916 kit on 915 trans, Who dunnit? Options

[East coaster]

I'm very happy with my Wevo 915 behind my 3.6. I thought about going with a beefed up 901, but felt I'd always be paranoid to really hit it hard and I couldn't see building a 3.6 914 that I had to baby.....just my $.02.

[Dr Evil]

Some really good info here. Thanks for sharing (IMG:style_emoticons/default/smile.gif)

[Joe Bob]

Deckman runs a 915 in his....

[Dr Evil]

Lightening the 1st and 2nd gears is done on the 901 gears as evidenced by the large groove on the undersides. I hadn't thought about that until you mentioned the 915 gears with the material removed.

[SirAndy]

I thought about going with a beefed up 901, but felt I'd always be paranoid to really hit it hard and I couldn't see building a 3.6 914 that I had to baby.....just my $.02.

(IMG:style_emoticons/default/confused24.gif)
I run a bone stock 901 behind my 3.6L and some of the local CA guys can tell you that i don't "baby" my car ... (IMG:style_emoticons/default/biggrin.gif)


Like i said earlier, as long as you don't use 1st gear, the 901 will last a long while for a fraction of the cost of a WEVO 915 ...
(IMG:style_emoticons/default/shades.gif) Andy

[PRS914-6]

I thought about going with a beefed up 901, but felt I'd always be paranoid to really hit it hard and I couldn't see building a 3.6 914 that I had to baby.....just my $.02.

(IMG:style_emoticons/default/confused24.gif)
I run a bone stock 901 behind my 3.6L and some of the local CA guys can tell you that i don't "baby" my car ... (IMG:style_emoticons/default/biggrin.gif)


Like i said earlier, as long as you don't use 1st gear, the 901 will last a long while for a fraction of the cost of a WEVO 915 ...
(IMG:style_emoticons/default/shades.gif) Andy

Yep, Andy is correct. There is no doubt that 1st is the weak part of the 901. It is cantilevered off the back with no support and pops off like a bottle top when abused. If you are willing to live with a 4 speed without the ideal gearing, it's certainly a smart decision when it comes to $$$$

As I stated earlier, losing a gear and living with a low 5th is not a a situation I wanted and the 915 build is VERY expensive. However, once you decide to regear, add posi etc you have to decide if you want to invest large sums of money to get a marginal tranny that can not use 1st for any abusive driving. Remember that when Porsche went to a 3.6 they went to a G50 tranny which is far better than a 915 and has a nice "overdrive" for the freeway. A G50 compared to a 901 is ....well it's not worth comparing.

Bottom line: The 915 is a very expensive compromise but you can get the gearing and strength to tolerate the torque of a 3.6 (barely). The light weight of the 914 saves most of the trannies anyway.

The 901 does not have the design to tolerate big torque in first and you will live with a 4 speed. However used 901's can be found for pennies. Regearing can be done but cost a lot and you still have the inherent weakness of first

So it ultimately boils down to $$$. The 915 is stronger, gears are easily available and all 5 speeds are usable for BIG $$ The 901 is dirt cheap, easy to find and easy to replace. Is it worth pouring money into? Only you can decide....... You could build at least 3 or 4 901s (or more) for the price of a WEVO 915

[Joe Bob]

The 915 is not a cure all. Weak point is the intermediate plate....the bearing shell gets loose and then the shaft flexes breaking second gear.

The fix involves pressing in a sleeve, new bearing and a WEVO or Guard GT bearing retainer that ties the two shafts together. BTDT.

The retainer is stock in the 930 and G-50 boxes.

[PRS914-6]

The 915 is not a cure all. Weak point is the intermediate plate....the bearing shell gets loose and then the shaft flexes breaking second gear.

The fix involves pressing in a sleeve, new bearing and a WEVO or Guard GT bearing retainer that ties the two shafts together. BTDT.

The retainer is stock in the 930 and G-50 boxes.

That's a point that I didn't even bring up.....The later 915's made out of aluminum eliminated the steel cast into the middle for the bearing bores. The bearing races are pressed into the bare aluminum. I haven't seen a high mileage aluminum 915 come apart that didn't have worn out bores. The solution is to buy the earlier magnesium trannies that have steel cast in at the bearing bores. They were used in the early 2.7 engines that were low powered and typically didn't see much abuse. I never understood the drive by everyone to get the aluminum 915's. Yes, aluminum is stronger but how often do you see a broken Mag unit? Add a one piece bearing retainer (more $$) and that problem is solved.

Indeed, every tranny alternative has a drawback or two and the 915 is certainly not exempt but probably a better starting point.

[pcar916]

The 915 is not a cure all. Weak point is the intermediate plate....the bearing shell gets loose and then the shaft flexes breaking second gear.

The fix involves pressing in a sleeve, new bearing and a WEVO or Guard GT bearing retainer that ties the two shafts together. BTDT.

The retainer is stock in the 930 and G-50 boxes.

That's a point that I didn't even bring up.....The later 915's made out of aluminum eliminated the steel cast into the middle for the bearing bores. The bearing races are pressed into the bare aluminum. I haven't seen a high mileage aluminum 915 come apart that didn't have worn out bores. The solution is to buy the earlier magnesium trannies that have steel cast in at the bearing bores. They were used in the early 2.7 engines that were low powered and typically didn't see much abuse. I never understood the drive by everyone to get the aluminum 915's. Yes, aluminum is stronger but how often do you see a broken Mag unit? Add a one piece bearing retainer (more $$) and that problem is solved.

Indeed, every tranny alternative has a drawback or two and the 915 is certainly not exempt but probably a better starting point.

There is one more cool thing about early 915's. They use the same carrier bearings, shims and spacers, and LSD as the 914 box. Why is that cool you ask?

I just put a new LSD into my 914 transaxle after 15 years of hard running. I also, over the years, acquired 2 early 915 boxes. One, with a not-so wonderful case, has a broken tooth on the pinion, but is otherwise in good shape. The other is very nice but neither has an LSD. A later reinforced side-cover and single-piece bearing retainer and I'm in business... ok I still have to install a shifter but I'm good. BTW they are both still 7:31 and yes... I know.

If I want to build one up for my 914 I'll transfer the LSD to it. Life is good sometimes. The moral of the story... always be lookin' for stuff.

[Steve]

The 915 is not a cure all. Weak point is the intermediate plate....the bearing shell gets loose and then the shaft flexes breaking second gear.

The fix involves pressing in a sleeve, new bearing and a WEVO or Guard GT bearing retainer that ties the two shafts together. BTDT.

The retainer is stock in the 930 and G-50 boxes.

That's a point that I didn't even bring up.....The later 915's made out of aluminum eliminated the steel cast into the middle for the bearing bores. The bearing races are pressed into the bare aluminum. I haven't seen a high mileage aluminum 915 come apart that didn't have worn out bores. The solution is to buy the earlier magnesium trannies that have steel cast in at the bearing bores. They were used in the early 2.7 engines that were low powered and typically didn't see much abuse. I never understood the drive by everyone to get the aluminum 915's. Yes, aluminum is stronger but how often do you see a broken Mag unit? Add a one piece bearing retainer (more $$) and that problem is solved.

Indeed, every tranny alternative has a drawback or two and the 915 is certainly not exempt but probably a better starting point.

There is one more cool thing about early 915's. They use the same carrier bearings, shims and spacers, and LSD as the 914 box. Why is that cool you ask?

I just put a new LSD into my 914 transaxle after 15 years of hard running. I also, over the years, acquired 2 early 915 boxes. One, with a not-so wonderful case, has a broken tooth on the pinion, but is otherwise in good shape. The other is very nice but neither has an LSD. A later reinforced side-cover and single-piece bearing retainer and I'm in business... ok I still have to install a shifter but I'm good. BTW they are both still 7:31 and yes... I know.

If I want to build one up for my 914 I'll transfer the LSD to it. Life is good sometimes. The moral of the story... always be lookin' for stuff.

Curious will the 7:31 915 ring and pin rev high in 5th like a 914 901 trans? I am running a 3.2 with a stock 901 trans and yes 5th gear is rather irritating on the freeway.

[PRS914-6]

the 7:31 box uses a taller 5th than the 8:31 but only because the R/P ration is lower. What I did was to take the taller 5th from a 7:31 box and used it in my 8:31 tranny. Gives a nice tall gear for 3.6 torque in a light car. Gets almost 30 mpg. Note the 8:31 is much stronger if you are running big torque.

Here is a chart for your review

[-JR-]

Paul are your 1st and 2nd gears custom machined by you or did you get these from a shop? Do you know if they required re-balancing after they were lightend?

I'm not sure if anyone here is with Patrick Motorsports, but I noticed that all of their big 6 street 914-6 cars are outfitted with 915's exclusively. I didn't even see one G50 despite all of the G50 goodies they make as well.

I've been thinking of the G50 as well, but I hear the G50 when inverted doesn't fit with the rear trunk also installed. I'm not into cutting up my project car's trunk.

I'm with Paul and East Coaster... When building a car like this and putting enough cash into it to make it nice... But then putting in a 901 only to not be able to use all that power at will. So if I have enough in my budget I will install a 915, but if I'm running short I'll run my 901 to get it going and upgrade to the 915 later.

[PRS914-6]

Running a 901 for awhile is actually a good move. You learn what you like and don't like about 901 gearing and can build a 915 accordingly. It's so expensive to build a nice 915 that when most people start adding up the cost they can't stomach it. I know I had that reaction at first but eventually just sucked it up. It can certainly exceed the value of the car or pay for a paint job. Here is what you are in for....

Core Tranny $500- $1000
First gear change (welded\changeable) $800\$1500
second gear $500
Misc bearings, syncros and dog teeth $1000
Used late style reinforced side cover $75-$100 or WEVO $300
WEVO kit $2000
5th gear (used early style) $200
Machine bolts and clearance case for R/P swap (estimate) $100
Rennshift $500 or used OEM 915 tower $100
Electric speedometer $75.00
R/P and carrier setup for proper load and clearance $250.00
One piece bearing retainer $200.00
Limited slip $1000
You assemble free/shop $500
Shift linkage?

And the list goes on. As you can see you are in for a $5k bill at the minimum. Swallow that one (IMG:style_emoticons/default/sad.gif)

The gears are made in Germany by custom gear manufacturers but can be bought from numerous vendors. A G50 is another matter especially since you will be required to use a cable shifter

[Steve]

[/quote]

There is one more cool thing about early 915's. They use the same carrier bearings, shims and spacers, and LSD as the 914 box. Why is that cool you ask?

I just put a new LSD into my 914 transaxle after 15 years of hard running. I also, over the years, acquired 2 early 915 boxes. One, with a not-so wonderful case, has a broken tooth on the pinion, but is otherwise in good shape. The other is very nice but neither has an LSD. A later reinforced side-cover and single-piece bearing retainer and I'm in business... ok I still have to install a shifter but I'm good. BTW they are both still 7:31 and yes... I know.

If I want to build one up for my 914 I'll transfer the LSD to it. Life is good sometimes. The moral of the story... always be lookin' for stuff.
[/quote]

I also have a 914 transaxle with an LSD. I am guessing that the 914 LSD would only work in a 7:31 915 Trans. The down side to that is the 5th gear is roughly the same in both boxes and would still rev high. Which is around 3500 RPMs at 80MPH. It would be nice to get 80MPH down to around 3000 RPM's in 5th.

[PRS914-6]

This is from memory....The early 915's I believe 915/02 and /06 is the same carrier size as the 914. These same trannies have the non bolt on front sleeve where the throw out bearing slides. They upgraded those trannies to a larger carrier bearings and being honest if you go to a 915 for big power, that's what you want. The 901 carrier bearings are really small for big HP. Unfortunately the 901 LSD won't fit the later 915's with the more appropriate and larger bearings. Again, that's from memory and I'm old.....

[Steve]

This is from memory....The early 915's I believe 915/02 and /06 is the same carrier size as the 914. These same trannies have the non bolt on front sleeve where the throw out bearing slides. They upgraded those trannies to a larger carrier bearings and being honest if you go to a 915 for big power, that's what you want. The 901 carrier bearings are really small for big HP. Unfortunately the 901 LSD won't fit the later 915's with the more appropriate and larger bearings. Again, that's from memory and I'm old.....

Thanks Paul!! BTW love the 3.6 project in excellence. Hopefully they will sell the series as a separate book, so we don't have to rip up a stack of magazines.

[turboman808]

I made a little price for a 915 build myself awhile ago with lots of wevo parts. It does really add up...

2000-transmission
2000-estimate for builder
895-gate shift
249
368
1975-side shift
oil system-700???
938-case mod 1
541-case mod 2
298-case mod 3

$$$9964

total estimate minus other parts like possible light weight gears that have been drilled.

quaife lsd $1648
shift tube and joint figure another $1000


roughly $12612 (IMG:style_emoticons/default/barf.gif)

[-JR-]

Paul you missed my question in my last post...

"Paul are your 1st and 2nd gears custom machined by you or did you get these from a shop? Do you know if they required re-balancing after they were lightend?"

Thanks!

[PRS914-6]

In my post above it says "The gears are made in Germany by custom gear manufacturers but can be bought from numerous vendors."

No balancing required and gear making is well beyond the average machinist. The holes are done in the machining process by the gear manufacturer. Basically you buy them and install them as is.

[-JR-]

In my post above it says "The gears are made in Germany by custom gear manufacturers but can be bought from numerous vendors."

No balancing required and gear making is well beyond the average machinist. The holes are done in the machining process by the gear manufacturer. Basically you buy them and install them as is.

Thanks Paul, I wasn't entirely sure what the context was for the statement in that post.