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914World.com _ 914World Garage _ 915 Transmission Questions
Posted by: iiibdsiil Dec 16 2005, 03:57 PM
What's the deal with the 915 transmissions? My 901 in with my 3.2 is screwed up, and I could get it repaired. Or, I could just upgrade and save myself some more headaches in the future.
What's a good price for a 915? Do I need to change anything to mate it to my 3.2? What years for the 915? Anything special I need to know?
Yes, I did a search, but I couldn't find much.
Thank you in advance guys!
Posted by: lapuwali Dec 16 2005, 04:14 PM
The chief issue with the 915 is getting a shift linkage to work. You can buy your way around the problem with WEVO parts. The 915 should bolt up to a 3.2, since that's what was in the 911 to start with. However, you'll need to swap back to a 915 flywheel and clutch from the modified flywheel you're running now.
Posted by: olav Dec 16 2005, 04:26 PM
What's screwed up and how did you do it?
Posted by: East coaster Dec 16 2005, 04:37 PM
Bring $$$$
I'm up to 9K so far and still don't have shift linkage!
Posted by: GeorgeRud Dec 16 2005, 04:45 PM
I switched to the 915, and have been very happy with it. I'm just running a 2.7, but am hoping to up that to a 3.2 or 3.6 this winter. The WEVO kit seems to be the best way to go, and the transmissions are pretty strong. You should be able to find a 915 for ~$1000 or less, but by the time it's rebuilt, the ring and pinion flipped, speedometer magnet ring pickup modified, etc., etc., it does run into some money.
I used the Vellios kit with good luck, but it did take a lot of car and measuring to get the linkage to work well. It really shifts nicely though, and I don't have to worry about ripping up the old 901 trans any more. Good Luck with your project!
Posted by: LvSteveH Dec 16 2005, 04:52 PM
Not to rain on anyone's WEVO inspired parade, but there are plenty of guys running around with home made linkage setups that work fine. It's just a little geometry, and small threaded rods with heim joint ends to actuate the gear selection properly. I know for a fact that several successful racers are doing just fine with it. It takes more time to set up initially, but any 915 with the ring gear flipped with work.
Posted by: GeorgeRud Dec 16 2005, 04:59 PM
I'd agree, the most difficult step was to get the linkage just right. Take the slop out of all the bushings and have the right sized metric tubing, and it works just fine.
If anyone made the side shifter parts available by themselves to fit a 915, a lot of money could be saved. I had to look long and hard to get the Vellios parts, but when we set up the transmission well, it worked great. It just seems that WEVO has done a lot of your homework for you, making it a more or less bolt in sort of setup. I personally enjoyed making up the linkage myself!
Posted by: jim912928 Dec 16 2005, 08:09 PM
Can anybody show us some pics of the "home made" solution? I'm keeping my 3.2l matched to it's 915..so I have to either do the wevo thing or maybe make my own? How did you fab the tranny mounts? Is it hard to flip the ring and pinion? What do you have to do for the speedo?
Jim
Posted by: JOHNMAN Dec 16 2005, 08:22 PM
Pic 1
Attached image(s)
Posted by: JOHNMAN Dec 16 2005, 08:23 PM
pic 2
Attached image(s)
Posted by: JOHNMAN Dec 16 2005, 08:24 PM
pic 3
Attached image(s)
Posted by: jim912928 Dec 16 2005, 08:41 PM
John...i should come and see this setup sometime. I work for harley davidson so I'm there at the kansas city plant occasionally.
Posted by: rick 918-S Dec 16 2005, 09:03 PM
Really cool!
Posted by: JOHNMAN Dec 16 2005, 09:46 PM
Um....
This is NOT my car.
I took pics of it at Heartland Park in Topeka last summer.
I liked what he did and plan on duplicating it on our future race car. I made some hand sketches and was going to draw it up and make me a BOM for the components needed, but so far I haven't had the time to reverse engineer it. (The stuff is still buried in my pile of projects to do on my desk...
I currently have a Vellios kit installed in the track car and it works excellent. I also have plans on converting another 915 with a second Vellios kit I have obtained. (This second will go in my street car currently slated for a 3.2 transplant when I get all my parts together. It will happen before spring.
If you are in the area (from HD, you could get to my house in less than 30 min.), feel free to contact me.
Last summer there was a second car with a home made linkage, but I liked this first one better.
Posted by: iiibdsiil Dec 17 2005, 09:58 AM
| QUOTE (olav @ Dec 16 2005, 05:26 PM) |
| What's screwed up and how did you do it? |
Drag racing
18 years old at the time, what did you expect?
Thanks guys, I didn't realize the conversion was so much work and money. I might start pricing it out though.
Post more pictures!
Posted by: rick 918-S Dec 17 2005, 10:12 AM
I'm confused.. What costs so much? 
I just went to car-part.com and did a search. Used boxes averaged $ 1250.00.....
What's involved in flipping the ring gear? 
Is the starter location the same as the 901-914 box? (flywheel diameter..?) 
Can you use the box on a 4 cylinder with a a stock flywheel?
Where can we find out about gear ratio's?
I need a "H" gear for 5th. Or something like it.
I'm thinking it will cost me a bunch of money to go through my stock box, maybe I should do this.. 
Is the box longer than a stock 914 box?
Posted by: J P Stein Dec 17 2005, 10:42 AM
Dunno bout youz guys, but I saved those linkage/mount pics to my files.
I have more fabricating skills than money. 
Posted by: rick 918-S Dec 17 2005, 11:02 AM
| QUOTE (J P Stein @ Dec 17 2005, 08:42 AM) |
| Dunno bout youz guys, but I saved those linkage/mount pics to my files. I have more fabricating skills than money. |
I did the same thing! 
Posted by: brp914 Dec 17 2005, 01:14 PM
| QUOTE |
| I'm confused.. What costs so much? I just went to car-part.com and did a search. Used boxes averaged $ 1250.00..... |
freshen/rebuild = several $1000's
wevo = $2000 (I'm goin' this way - more $ than fab skills here)
axles/cv = several $100's
915 style shifter = several $100's
tranny mounts
exhaust/muffler (wevo will interfere w/stock muffler)
shift linkage
clutch/flywheel/clutch linkage
electronic speedometer
starter
flip r&p
modify side cover for speedo
tb diff? = $1500+
I'm in process now - will post soon...
Posted by: rickyhgarcia Dec 17 2005, 01:58 PM
| QUOTE |
| I need a "H" gear for 5th. Or something like it. |
I bought my 5th H gear from Brad Mayeur ( 914ltd@earthlink.net ) for about $300.00.
Posted by: rick 918-S Dec 17 2005, 05:20 PM
| QUOTE (rickyhgarcia @ Dec 17 2005, 11:58 AM) | ||
I bought my 5th H gear from Brad Mayeur ( 914ltd@earthlink.net ) for about $300.00. |
Ya, I have an HB. But does anyone know what the 5th gear is in the 915?
Posted by: rick 918-S Dec 17 2005, 05:27 PM
| QUOTE (brp914 @ Dec 17 2005, 11:14 AM) | ||
freshen/rebuild = several $1000's wevo = $2000 (I'm goin' this way - more $ than fab skills here) axles/cv = several $100's 915 style shifter = several $100's tranny mounts exhaust/muffler (wevo will interfere w/stock muffler) shift linkage clutch/flywheel/clutch linkage electronic speedometer starter flip r&p modify side cover for speedo tb diff? = $1500+ I'm in process now - will post soon... |
Car-part.com. Rebuilt listed for sale $ 1650.00.
I'm talking a good used box $ 1250.00 Ready to flip the R&P.
Are you saying it costs $ 1000.00 to dismantle a box, flip the R&P and reassemble?
I just read the bolts need to be machined to clear the cover and maybe something about machining a little clearance in the box. I can't imagine it would cost $ 1000.00.
I have a good clutch.
And oh ya, I have skills.
Sounds like your doing a bunch of stuff that wouldn't normally need to be done to convert the average 914.
Why are you converting to an electric speedo?
Whats special about the starter?
I bought my 911 starter from Oklahoma foriegn for $ 50.00 no core. It had a Bosch rebuilt tag on it.
Posted by: McMark Dec 17 2005, 05:38 PM
I've been led to believe that 915s have a bearing race issue that makes used trannys untrustworthy. Of course you can always run it till it explodes.
Posted by: anthony Dec 17 2005, 05:40 PM
At minimum, most 915s (even good used ones) probably need synchros and dog teeth for 1st and 2nd. Then if you start doing the "while you are in there" stuff you'll easily speed $2K for a very basic refresh.
Posted by: SirAndy Dec 17 2005, 05:42 PM
| QUOTE (McMark @ Dec 17 2005, 04:38 PM) |
| I've been led to believe that 915s have a bearing race issue that makes used trannys untrustworthy. |
yes, a lot of them do. the 915s are getting old as well ...
most of the used ones will need a rebuild, and a lot of them have the "bearing race" issue.
Andy
Posted by: dwillouby Dec 17 2005, 05:58 PM
Check with Rod Simpson. I believe he has the shift linkages and mounts. I saw them at his shop a few years ago.
David
Posted by: rick 918-S Dec 17 2005, 06:05 PM
Sounds like a negociation opportunity. So lets say you don't get Dirk Wrights disease.... and you just flip the R&P, install the box and use it. Sounds like you could blow the first box up twice before you've spent the cost of a rebuild. What are the odds of getting three bad boxes in a row..
We are 914 people------People. I'm looking into this.
Back to the questions;
Is there a site that lists 5th gear letters for the 915 by year?
Anyone know if the 915 box has a 5 gear near "H"
Oh, this may be the wrong question.
First; what is the R&P ratio of the 901/914 box?
then I found this;
The 915 appeared in 1972 with a major upgrade in strength, compared to its predessor. The first ones didn't shift as well as the later ones due to some improvements in the shifter and syncro's. 915's were made with magnesium cases from 72 until 77. Some of them had aluminum final-drive cases in 77 before the entire gearcase was made from aluminum in 1978. 915's used 7:31 ring & pinions until 1975 when they switched to the stronger 8:31. These later ring & pinions are the preferred item for racing or high-horsepower applications and the later 915's had stronger differentials and mainshafts.
I attached the link to a Lambo conversion site.http://www.rennsportsystems.com/1-d.html
Posted by: jim912928 Dec 17 2005, 06:13 PM
Rick,
When I get back up to Milwaukee sunday night I'll pull my 911 manuals and my SC and Carrera manuals and get the gear info. All I know is that when I drive the 911SC the gearing is great....car is not screaming in 5th at 90 and you don't shift out of 1st the minute you put your foot in the gas. I took the donor 3.2l car out last month (was starting to think 901 for this springs project) and was at 60 or so and still in 2nd gear...no more thoughts of the 901! After driving both 911's and seeing how well the tranny and gear ratio's seem to be aligned I don't think I'd want to bother hooking up my 901 to the 3.2l engine.
Posted by: jim912928 Dec 17 2005, 06:16 PM
ahhh...looks like the gearing info is in the link that Rick put in his last message.
Posted by: rick 918-S Dec 17 2005, 06:25 PM
| QUOTE (jim912928 @ Dec 17 2005, 04:13 PM) |
| Rick, When I get back up to Milwaukee sunday night I'll pull my 911 manuals and my SC and Carrera manuals and get the gear info. All I know is that when I drive the 911SC the gearing is great....car is not screaming in 5th at 90 and you don't shift out of 1st the minute you put your foot in the gas. I took the donor 3.2l car out last month (was starting to think 901 for this springs project) and was at 60 or so and still in 2nd gear...no more thoughts of the 901! After driving both 911's and seeing how well the tranny and gear ratio's seem to be aligned I don't think I'd want to bother hooking up my 901 to the 3.2l engine. |
See, that's what I was thinking.
The 901 seems to be better suited to the 4 cylinder task. We can use them with our V8's but the RPM's are up there on the freeway.
When I was coming from Mike Ginters house heading for Vegas for the WCC "05" I ran the Alien up over 100 on a long section of open highway. I probably held it there for 30 miles before I backed down. I don't have a tach but based on my years of Big Block Chevy's I'd say I was twisting 5000 to 5500 RPM's. Based on the cost to go through my sick 901, I think I could change to the 915, fab some new linkage and be in better shape over the long haul.
Posted by: rick 918-S Dec 17 2005, 06:27 PM
| QUOTE (jim912928 @ Dec 17 2005, 04:16 PM) |
| ahhh...looks like the gearing info is in the link that Rick put in his last message. |
Ya, But how does that compare to the 901?
Posted by: JOHNMAN Dec 17 2005, 06:31 PM
A 915 shifter should be able to be had for $150 or so,
The axles can be made from 914 axle shafts (with a little machining) and 911 (or 944) CV joints (depending on the splines on the axle shaft).
A shift rod would need to be created.
A way to release the clutch would need to be fabbed as well.
I know for a fact that I can fabricate or modify all these parts.
I think that the stock 915 gearing (1984-1989) is similar to the stock 914/901 gearbox. I may be wrong, but I didn't notice much if any difference in gearing when we switched from the 914/901 to a 915 in the race car. (3.2)
just my $0.02
I may be able to scrounge a few more pics of linkages. I just have too many pics to search......
I can't believe I am the only one with pics of such linkages.
Posted by: JOHNMAN Dec 17 2005, 06:36 PM
You know, this same fabricated linkage and support could be applied directly to 930 transmissions as well (for those V8 guys).
On another note, The starter is in exactly the same place as on a 914/901, but I couldn't tell you if you could bolt it up and use a stock 4-cyl flywheel. I know it will bolt to the 4-cyl, and AFAIK the 914-4 and 914-6 used interchangable starters, so I would venture to guess that the starter would work with a 4-cyl flywheel.
Posted by: rick 918-S Dec 17 2005, 06:37 PM
I bet Brad has some but he's too busy... 
I bet he could answer all our questions too...
Posted by: jim912928 Dec 17 2005, 06:40 PM
901 gears off of PET for a 75 914
1st: 11:34
2ND: 18:34
3rd: 23:28
4th: 27:25
5th: 31:22
ring gear: 7:31
915 gears off of PET for an 84 911
1st: 11:35
2nd 18:32
3rd 23:29
4th: 26:26
5th: 38:30
ring gear: 8:31
Posted by: spare time toys Dec 17 2005, 06:43 PM
| QUOTE (jim912928 @ Dec 17 2005, 07:40 PM) |
| 901 gears off of PET for a 75 914 1st: 11:34 2ND: 18:34 3rd: 23:28 4th: 27:25 5th: 31:22 ring gear: 7:31 915 gears off of PET for an 84 911 1st: 11:35 2nd 18:32 3rd 23:29 4th: 26:26 5th: 38:30 ring gear: 8:31 |
I may be doing the math wrong but wouldnt those make RPM higher with the 915
Posted by: JOHNMAN Dec 17 2005, 06:54 PM
| QUOTE |
| I may be doing the math wrong but wouldnt those make RPM higher with the 915 |
I think it is ever so slightly lower RPM with the 915, but like I said before, I didn't notice that much difference in gear ratios when we did the swap. (1974 914/901 to 1986 915)
Posted by: rick 918-S Dec 17 2005, 06:56 PM
Anyone know what gear set makes the 38:30 5th gear ratio?
Posted by: rick 918-S Dec 17 2005, 06:57 PM
Someone had a link to a gear set chart... Aaron?
Posted by: sj914 Dec 17 2005, 07:12 PM
http://www.pelicanparts.com/techarticles/mult_tranny_ratios/mult_tranny_ratios.htm
Here's the charts.
Posted by: rickyhgarcia Dec 17 2005, 08:13 PM
5th Gears
24:27 1.13
25:27 1.08
25:26 1.04
26:26 1.00
26:25 0.96
27:25 0.93
27:24 0.89
28:24 0.86
29:23* 0.79
29:22 0.76
29:21* 0.72
31:21 0.68
32:20 0.63
from www.powerhausii.com
Posted by: J P Stein Dec 17 2005, 08:36 PM
| QUOTE (spare time toys @ Dec 17 2005, 04:43 PM) | ||
I may be doing the math wrong but wouldnt those make RPM higher with the 915 |
Using the same rpms, the 8:31 in the 915 represents about a 11% increase in speed over the 7:31.... per gear.
Posted by: brp914 Dec 17 2005, 09:13 PM
| QUOTE |
| Sounds like your doing a bunch of stuff that wouldn't normally need to be done to convert the average 914. |
yeah, for instance?
| QUOTE |
| Why are you converting to an electric speedo? |
my 915 is already elec. speedo. even if you get an early box w/ mech speedo, its in the wrong place, and I doubt it will hook up to 914 cable, and if it did the speedo will be wrong.
| QUOTE |
| Whats special about the starter? |
nothing special, its just different than my 914 one
| QUOTE |
| Are you saying it costs $ 1000.00 to dismantle a box, flip the R&P and reassemble? |
no. if you dismantle, bring it for r&p flip and machining, then you reassemble, prolly half that.
| QUOTE |
| Car-part.com. Rebuilt listed for sale $ 1650.00. |
whats the core charge? dunno about you, but I'm wary of generic rblts. what does rblt mean? If you look at the cost of parts, you'll find that rblt isn't buying you much.
regarding shift linkage, just cuz some guy hooks up some rods and joints, doesn't mean it works well. Probably shifts like crap. even a lot of the vellios could barely be made to work. you can try to go cheap, but I'm guessing it wont be reliable and/or enjoyable to drive.
Posted by: JOHNMAN Dec 17 2005, 09:59 PM
| QUOTE |
| just cuz some guy hooks up some rods and joints, doesn't mean it works well. Probably shifts like crap. even a lot of the vellios could barely be made to work. you can try to go cheap, but I'm guessing it wont be reliable and/or enjoyable to drive. |
On this point we obviously differ in opinion. The pics that I posted were of a race car that worked incredibly well. The linkage took lots of time setting up initally and he swapped the pressure plate to a different style, but other than that it worked and felt as positive as any 911 shifter that he had used. From seeing that linkage in person, and making some sketches, I am convinced that there is no reason why it wouldn't be a solid and reliable linkage.
I agree with you that the low budget "rebuilds" are probably not rebuilt well and are more likely just expensive cores, and that this is definately not an inexpensive modification to make.
Posted by: rick 918-S Dec 17 2005, 10:04 PM
Dude... Have you seen my car? 
I made everything from the engine mounts to the nylon throttle cable bushings
I drove from MN to Southern Cali., Ran the car at Willow and drove home.
You can get Dirk Wrights Disease or you can drive your car some day...
Posted by: Aaron Cox Dec 17 2005, 10:15 PM
all this talk about 901's being geared wrong blah....
jim912928... you are using a 4 CYLINDER 914 box as a comparison? how is that fair to the 901?
pick up a 914/6 box, and your 2nd gear ratio would be taller (like you said "60 in second" ) and you would need a taller 5th, (flipped H , HA, HB) for your desired cruising rpm.....
just asking for ya to be fair in your comparisons... a /6 box with a taller 5th would be fine...but you want to side step the clutch and drag race... a 915 is for ya...
i dont know about you all....
ill blow up 7 or 8 901's before id pay for a 915....
a few people (racers) are running 3.6+ motors through 901's.......
just my opinions....
AA
Posted by: rick 918-S Dec 17 2005, 10:28 PM
| QUOTE (Aaron Cox @ Dec 17 2005, 08:15 PM) |
| all this talk about 901's being geared wrong blah.... jim912928... you are using a 4 CYLINDER 914 box as a comparison? how is that fair to the 901? pick up a 914/6 box, and your 2nd gear ratio would be taller (like you said "60 in second" ) and you would need a taller 5th, (flipped H , HA, HB) for your desired cruising rpm..... just asking for ya to be fair in your comparisons... a /6 box with a taller 5th would be fine...but you want to side step the clutch and drag race... a 915 is for ya... i dont know about you all.... ill blow up 7 or 8 901's before id pay for a 915.... a few people (racers) are running 3.6+ motors through 901's....... just my opinions.... AA |
That's tellen us Aaron! But do you know what letter the 5 gear is in the 915? All the charts have the gear ratios listed but no letter..
Posted by: nine14cats Dec 17 2005, 10:29 PM
I just went through a full 915 WEVO box upgrade with about every option known to man and the price tag can add up. It's just what you want from the box that will determine the price.
Flipping the ring and pinion for mid-engine will run 2 to 4 hours of labor if your paying for it. Clearancing does need to be done inside the transaxle because of the flip of the R&P. It's minimal, but needs to be done. A hole needs to be machined in the other side of the box for the magnet of the speedo if you choose to run it. That is another 2 to 4 hours of labor if you go that route.
For shift linkage I went with the WEVO setup. If you go this route, the actuating lever (dongle) inside the trans is swapped out for a shorter piece from WEVO. WEVO takes the old dongle as a core. If you do not want to spring for a WEVO tail housing, Rod Simpson's linkage is based on the 901 tail shifter linkage geometry. I talked with Rod at length when I was researching which way to go. His linkage is very competitively priced if you are on a budget.
Both Renegade and Patrick Motorsports also sell cable shifter setups for the boxes. I don't know how they compare in price.
If you get into the box for synchro's, bearings, gears, etc., it adds up since it's a $100 here and there and it just adds up. Additionally, I had a bad bearing housing in mine, so that was replaced as well.
Minimally, if you have a good working 915 to start, you can flip the R&P, have the speedo machined and use Simpson's linkage and be on the road for ~$1500, not counting the cost of the 915. On the other end of the spectrum, my race box WEVO cost $8K not including the cost of the box. But this was for a pure track car and as I stated above, a street car version can be had for a reasonable price.
FWIW, the WEVO tail piece is a thing of beauty! So far, everyone I know that runs it has good things to say.
Bill P.
Posted by: Aaron Cox Dec 17 2005, 10:30 PM
915's dont have names im aware of...just ratio's (which is all that matters no???)
AA -> 901 fan
Posted by: rick 918-S Dec 17 2005, 10:36 PM
| QUOTE (Aaron Cox @ Dec 17 2005, 08:30 PM) |
| 915's dont have names im aware of...just ratio's (which is all that matters no???) AA -> 901 fan |
Ya, But I was wondering if the HB gear I have is equal to the 5th gear ratio in the 915 box.
I'm clueless. 
Posted by: Aaron Cox Dec 17 2005, 10:37 PM
| QUOTE (Aaron Cox @ Dec 17 2005, 09:30 PM) |
| 915's dont have names im aware of...just ratio's (which is all that matters no???) AA -> 901 fan |
im a doof...
cut from carquip website....
Attached image(s)
Posted by: TimT Dec 17 2005, 10:45 PM
901s had letter names to the gear set,
915s they just published numerical ratios
Find what an HB is numerically and find a matching 915 gearset
Also the R&P ratio on 915s and 901s are the same 7:31, unless a special ratio was ordered.
Also the gear sets in 901 and 915 changed almost yearly, as new more powerful engines were brought online, the transmissions were geared to take advantage of the additional power
and bottom line 915 transmissions are stronger than 901s
I do have a 901 bolted to my modded 3.2, but I have a transmission on standby, and a few parts transmissions at hand also
Posted by: jim912928 Dec 17 2005, 10:47 PM
Aaron,
I wasn't really trying to compare them to start any controversy...just my seat experience of driving my 911's versus driving my 914. It's about the tall gearing for highway speeds for me. I have a 3.2l engine to put in my 914 that already has a rebuilt 915 attached to it...I'm just planning on keeping them mated since they were made for each other versus cutting on my 901 to fit the sensors and putting in a taller 5th gear. Just adding an opinion. I do hear too many talk about the gearing for cruising at highway speeds as an issue with the 901's (which I do alot of highway driving). With the taller 5th and the different sized ring gear...seems like my 915 will be better suited for me.
Jim
Posted by: Aaron Cox Dec 17 2005, 10:48 PM
| QUOTE (TimT @ Dec 17 2005, 09:45 PM) |
| 901s had letter names to the gear set, 915s they just published numerical ratios Find what an HB is numerically and find a matching 915 gearset Also the R&P ratio on 915s and 901s are the same 7:31, unless a special ratio was ordered. Also the gear sets in 901 and 915 changed almost yearly, as new more powerful engines were brought online, the transmissions were geared to take advantage of the additional power and bottom line 915 transmissions are stronger than 901s I do have a 901 bolted to my modded 3.2, but I have a transmission on standby, and a few parts transmissions at hand also |
werd...915 is stronger.... but a pita and the wallet to utilize...
rick ollah.... a flipped HB is a ... 31:19
| QUOTE |
| Flipped HB 5 31 : 19 (0.613) |
Posted by: TimT Dec 17 2005, 10:57 PM
Use a gear calculator to put together your gearsets. I thought there was an Excel spreadsheet in the download area.. if not I have a couple of gear calculators I cen email
You enter tire diameter, final drive ratio, redline, shift points.. then plug in gears and see how they work..
Posted by: Aaron Cox Dec 17 2005, 10:59 PM
| QUOTE (TimT @ Dec 17 2005, 09:57 PM) |
| Use a gear calculator to put together your gearsets. I thought there was an Excel spreadsheet in the download area.. if not I have a couple of gear calculators I cen email You enter tire diameter, final drive ratio, redline, shift points.. then plug in gears and see how they work.. |
tim... i think i have most of the data charts you have...
mind sending me what you got?
acox914@comcast.net
Posted by: TimT Dec 17 2005, 11:04 PM
They are excel spreadsheet been around for awhile. Ill email them, but Ill have to fire up some of my laptops and see which one they are one
but yea Ill shoot them over to you tomorrow maybe
Posted by: Aaron Cox Dec 17 2005, 11:08 PM
| QUOTE (TimT @ Dec 17 2005, 10:04 PM) |
| They are excel spreadsheet been around for awhile. Ill email them, but Ill have to fire up some of my laptops and see which one they are one but yea Ill shoot them over to you tomorrow maybe |
coolio.
i think i have all the same ones... but its good to check
thanks tim
AA
Posted by: Britain Smith Dec 17 2005, 11:18 PM
I have every calculation sheet for every 901 and 915 version...let me boot up my laptop...hold on.
-Britain
Posted by: J P Stein Dec 17 2005, 11:23 PM
| QUOTE (Britain Smith @ Dec 17 2005, 09:18 PM) |
| I have every calculation sheet for every 901 and 915 version...let me boot up my laptop...hold on. -Britain |
Ah, Britian lives.
What's going on with the 912?
Posted by: rick 918-S Dec 17 2005, 11:24 PM
Thanks for all the great info guy's!
My head is swimming
If I'm reading this correctly the 901 ZD gear is the same ratio as the 5th gear in the 915. Looks like they both have the same R&P so I'm not saving anything by buying a 915. I will have to have the R&P flipped, machine work done, install my HB gear, shorten the bellhousing for my conversion, build a tranny mount, build linkage, have a custom speedo cable made, adapt axles, etc,
I guess my 901 goes out for a build.
But I like that cool linkage!
Posted by: Aaron Cox Dec 17 2005, 11:29 PM
| QUOTE (rick 918-S @ Dec 17 2005, 10:24 PM) |
| Thanks for all the great info guy's! My head is swimming If I'm reading this correctly the 901 ZD gear is the same ratio as the 5th gear in the 915. Looks like they both have the same R&P so I'm not saving anything by buying a 915. I will have to have the R&P flipped, machine work done, install my HB gear, shorten the bellhousing for my conversion, build a tranny mount, build linkage, have a custom speedo cable made, adapt axles, etc, I guess my 901 goes out for a build. But I like that cool linkage! |
a 901 gear wont fit on a 915........
ZD 5 is too short for small tires and high freeway speeds on a 901.....
thus flipped H, HA, HB applications....
use the 901
be donePosted by: Britain Smith Dec 17 2005, 11:37 PM
Ok, here is an article of every Porsche tranny ratios:
Page1:
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Posted by: Britain Smith Dec 17 2005, 11:37 PM
Page 2:
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Posted by: Britain Smith Dec 17 2005, 11:40 PM
Just in case you wanted to know the Cayenne ratios...its on there.
Now for the calculation sheets...they are in excel format and I am not sure if they will load here...lets try the first one.
-Britain
Nope...won't do it. Let me load them to my site.
Posted by: Aaron Cox Dec 17 2005, 11:42 PM
thanks for sharing brittain
AA
Posted by: rick 918-S Dec 17 2005, 11:43 PM
Wow! Cool!
Posted by: Britain Smith Dec 17 2005, 11:43 PM
| QUOTE (J P Stein @ Dec 17 2005, 10:23 PM) | ||
Ah, Britian lives. What's going on with the 912? |
Hey JP!
Not much going on here...freezing my ASS off!
I need to get a heater in the garage...it is just too damn cold to work out there.
My new years resolution is to get the car running...wanna help?
You getting your car back together? Let me know when you are putting the tranny back in, I will come up and help out.
-Britain
Posted by: Britain Smith Dec 17 2005, 11:46 PM
Alright, this is what I got.
All the files are located here:
http://britainsmith.com/Porsche/TransmissionCalc/
FYI: You have to right click the files and save to your computer...
Now, I made these some time ago. Let me know if you have any issues. Remember to enter the correct tire sizes (i.e. 205/50/15) to make the speed calculations work. Also, these sheets are based off engine RPM and torque values.
-Britain
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Posted by: Britain Smith Dec 17 2005, 11:51 PM
Just is case...here are some instructions:
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Posted by: Britain Smith Dec 17 2005, 11:55 PM
Also, remember to check the tabs at the bottom...there are additional charts.
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Posted by: Britain Smith Dec 17 2005, 11:55 PM
Another...
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Posted by: Britain Smith Dec 17 2005, 11:55 PM
Last...
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Posted by: davec Dec 18 2005, 12:02 AM
I have both the 916 transmission and a Velios conversion. Both have been worked on extensively.
The Velios is in the race car and is the smoothest shifting transmission you could imagine. It has the stock 915 shifter, relocated back about 2 inches. It also includes a spray bar, which helps keep the temp down to around 230 degrees on hot track days.
The 916 is an interesting tranny in that the magnesium conversion parts were made by Porsche (later copied by Velios, with improvements). They had some inherent problems (two gears at once- leaks) but were made with stock SC gear ratios. That combo is great with my 2.7l. I use a Wevo shifter, but made the rods from "73" pieces. They were a pita to set up, but it now shifts fine.
For the 915 in general, you get a better shifting pattern! 3d and 4th are on the same shifting plane, very handy at the track. But my main point is that you can still buy the 916 tranny: they only made, what, 11 of the cars, but a slew of the transmissions. And I know of a fellow in PA who claims to have 2 of them for sale. He mentioned $2500, and all the tough work is done.
Once you blow up an engine with an antiquated 901 tranny with a mystery shifter, you tend to look for a better way. Now, if I could only find a good sequential box...
Posted by: jim912928 Dec 18 2005, 09:01 AM
Rick,
FYI so you make the right decisions. The ring gear is NOT the same ratio's at the 901 on the 78 and newer 915's. In 1978 the factory switched to an 8:31 from the previous 7:31's. This will help you out with your higher speeds and the later 915's taller 5th gear.
Jim
.
Posted by: jim912928 Dec 18 2005, 09:14 AM
Here is the explosion of an 84 915 gear set:
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Posted by: ClayPerrine Dec 18 2005, 09:41 AM
FYI... for those of you who were toying with the idea of tying a 915 to a 4 cylinder..... the factory did that. The results were called a 912E.
The 912e uses a special input shaft and clutch release arm to work with the 215mm 914 clutch setup. Both parts are very rare and expensive.
Posted by: rick 918-S Dec 18 2005, 09:44 AM
| QUOTE (jim912928 @ Dec 18 2005, 07:01 AM) |
| Rick, FYI so you make the right decisions. The ring gear is NOT the same ratio's at the 901 on the 78 and newer 915's. In 1978 the factory switched to an 8:31 from the previous 7:31's. This will help you out with your higher speeds and the later 915's taller 5th gear. Jim . |
Oh... So Who can calulate this? I wouldn't know how to do it if the instructions were on the back.
box (1) is 901 with an "HB" 5th gear.
box (2) is a 915 with the higher 8:31 final drive
Car has 28" tall tires
Q.) What is the RPM's at say 75 mph?
Does this seem like school to anyone?
Posted by: rick 918-S Dec 18 2005, 09:47 AM
| QUOTE (ClayPerrine @ Dec 18 2005, 07:41 AM) |
| FYI... for those of you who were toying with the idea of tying a 915 to a 4 cylinder..... the factory did that. The results were called a 912E. The 912e uses a special input shaft and clutch release arm to work with the 215mm 914 clutch setup. Both parts are very rare and expensive. |
Oh... see that's the kind of info we need. So if I got this right, there is definitely going to be the need to run a different pressure plate and "T" bearing.
Is that right?
Posted by: ClayPerrine Dec 18 2005, 10:06 AM
Nope. If you are using the 4 cylinder pressure plate and throwout bearing, you can use that with the 912E transmission.
But you have to find a 912E transmission first......
Posted by: rick 918-S Dec 18 2005, 10:16 AM
| QUOTE (ClayPerrine @ Dec 18 2005, 08:06 AM) |
| Nope. If you are using the 4 cylinder pressure plate and throwout bearing, you can use that with the 912E transmission. But you have to find a 912E transmission first...... |
wise guy!
Posted by: Aaron Cox Dec 18 2005, 11:31 AM
| QUOTE (rick 918-S @ Dec 18 2005, 09:16 AM) | ||
wise guy! |
the type 923
all of what 3000 912E's made or something?
Posted by: Britain Smith Dec 18 2005, 12:23 PM
You mean one of these...
This is my 923 Transmission. I got it as a core in nasty shape for $750 (from HPH). I replaced the 1/2 syncros and upgraded the 3/4 slider to the late model style. It was rebuild by WEVO with WEVO goodies. If you look closely, all of those screenshots of sheets I posted above where from the 923 transmission.
You are right, it has a 901 mainshaft and using a early 911 or 914 215mm clutch set-up. This particular one had the crossover point on the bottom where the cable goes knock off. I had to have it magnesiem welded. Here is a picture before I cleaned it up completely. 
This tranny also has a taller 5th gear that allows it to travel at highway speeds and the engine to not be screaming. 
It will go nicely with this:
Posted by: Britain Smith Dec 18 2005, 12:24 PM
| QUOTE (Aaron Cox @ Dec 18 2005, 10:31 AM) | ||||
the type 923 all of what 3000 912E's made or something? |
Actually, IIRC there there 2199 made.
I know where two of these transmission are possibly.
-Britain
Posted by: Dinobx Jun 24 2006, 07:10 PM
Hey all,
Have any of you ever had any experience with Rod Simpson's 915 shift kit?
Thanks.
Dino
Posted by: TimT Jun 24 2006, 07:39 PM
errrrrrrrr
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