 Flipping the gears |
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| Bleyseng |
 Jun 14 2003, 12:52 PM
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#1
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Aircooled Baby!  Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest  |
Well, I have been busy rebuilding a transmisson and went ahead with flipping 5th and 3rd gears for AXing. It's been interesting to say the least but not too hard. Here is a shot of the assembled gear stacks.
Geoff Attached image(s) 
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| seanery |
Jun 14 2003, 12:59 PM
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#2
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
I don't really get what you get out of doing this.
Can you put it in Moron terms? |
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| Bleyseng |
Jun 14 2003, 01:49 PM
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#3
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
A close ratio tranny. By flipping 5th into 3rd's place you get a shorter gear. So 5th gear is then also a little shorter too but I don't go 120mph anyway.
Right now AXing, the problem is when to shift to 3rd, we are reving 2nd out to 5000 but sometimes the drop seems too great when you hit 3rd gear unless its a long stretch on course. Soo, you kinda hang at there trying to decide should I shift or not...then the rev limiter hits (5800) so you know you are losing time. I have a chart on the other computer I can't get too to show the change.. I look for it online. I am rebuilding this orginal to the car tranny because the other one is having problems. (bearings) Geoff |
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| Bleyseng |
Jun 14 2003, 01:56 PM
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#4
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
The chart:
Attached thumbnail(s) 
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| ChrisReale |
Jun 14 2003, 03:51 PM
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#5
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Sleazy Group: Members Posts: 2,665 Joined: 20-January 03 From: San Francisco Member No.: 176 |
So, instead of just replacing 5th with another 5th, yo are using the flipped third? Is the tranny together yet? How does it drive? When are we doing mine? (IMG:style_emoticons/default/smash.gif)
I just ordered a set of Panasport wheels and V Racers (IMG:style_emoticons/default/boldblue.gif) |
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| Dave Cawdrey |
Jun 14 2003, 04:31 PM
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#6
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Dumbo going poop, Daddy :) Group: Members Posts: 818 Joined: 22-January 03 From: Seattle, WA USA Member No.: 182 |
On/in my future setup, I will have a 78 stroke. Thus, giving me a bit more low end UMPF...
My thinking, flipping would not benefit me. Or am I another moron? Enlighten me... |
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| tat2dphreak |
Jun 14 2003, 06:03 PM
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#7
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region  |
I already know I'm a moron... but humor me, doesn't that take out your top end?
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| TimT |
Jun 14 2003, 07:41 PM
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#8
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
Using the stock gears on the track or at an AX you will never ever see the "top speed" of the car.
For a race car you gear the transmission so you can use all the gears. The 901 based gear boxes offer a wide range of gear choices. porsche designated them alphabetically A through ZD (I think) some gears are very rare and costly. A easy way to fill the hole ion your gear selection is by inverting a gear take a Z (29:23) and flip it you now have almost an M (22:29) There is no reason at all to have gears to go 155 mph if you dont have the power to get the car there. My cars are geared to a max of about 145, but I can use all 5 gears.... The RPM drops on each shift decrease in a good way... 2-3rd is about 1000, 3-4th is about 800 ,4-5th is about 600.. This keeps the car in its power band.. The faster the car is going the harder it is to push through the air.... hence wanting less rpm drops. close ratio gears lets you get the most out of your engine.. |
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| Aaron Cox |
Jun 14 2003, 07:45 PM
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#9
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
do you have a "street" trans, and a "race" trans? or just one total
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| tat2dphreak |
Jun 14 2003, 08:30 PM
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#10
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region |
(IMG:style_emoticons/default/huh.gif)
ok, now I get it, thanks.... as I said, I know I'm a moron esp. when it comes to AutoX... |
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| Dave Cawdrey |
Jun 14 2003, 09:08 PM
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#11
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Dumbo going poop, Daddy :) Group: Members Posts: 818 Joined: 22-January 03 From: Seattle, WA USA Member No.: 182 |
QUOTE(TimT @ Jun 14 2003, 05:41 PM) Using the stock gears on the track or at an AX you will never ever see the "top speed" of the car. For a race car you gear the transmission so you can use all the gears. The 901 based gear boxes offer a wide range of gear choices. porsche designated them alphabetically A through ZD (I think) some gears are very rare and costly. A easy way to fill the hole ion your gear selection is by inverting a gear take a Z (29:23) and flip it you now have almost an M (22:29) There is no reason at all to have gears to go 155 mph if you dont have the power to get the car there. My cars are geared to a max of about 145, but I can use all 5 gears.... The RPM drops on each shift decrease in a good way... 2-3rd is about 1000, 3-4th is about 800 ,4-5th is about 600.. This keeps the car in its power band.. The faster the car is going the harder it is to push through the air.... hence wanting less rpm drops. close ratio gears lets you get the most out of your engine.. Tim, After reading your post, I am thinking that flipping or changing will benefit me (see my first thought above). See, I am building this car for a specific driver. He is an excellent driver. I feel comfortable sacrificing a little high end for a bit more torque and bite in the bottom end ONLY because he (the driver) can handle all the extra "squirliness" in the tight corners. Constant shifting (up/down) will be smooth thanks to Rennshift. So, am I correct in my thinking now? That, due to the fact that I could shift sooner, the RPM's drop less, and use 3rd and 4th rather than 2nd and 3rd. Then again, with the closer ratio gearing, you'd be finished shifting and have to start the next shift (IMG:style_emoticons/default/wacko.gif) |
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| Bleyseng |
Jun 14 2003, 11:06 PM
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#12
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
The idea as TimT said is to stay in the power band with your gearing. I know top hp for me is 5200 so I want to shift just after that and be in the engines power in 3rd without it dropping revs too far drop out of the top power range. Anywho, I am giving it a try. Nothing lost, nothing gained.
Aaron, I do have another street tranny in the car. It needs attention real soon! That is why I pushed doing the AX tranny now as the next race is on June 21st. Korijo, I don't have any idea what the power band of your motor will look like other than with all that stroke I would think it would be at lower rev's. Depends on the cam too. Jake Raby puts in a mild cam for bus motors so all the torque is down low. For the bugs he runs those 86a combo's which moves the band up higher. Geoff (IMG:style_emoticons/default/aktion035.gif) |
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| Dave Cawdrey |
Jun 15 2003, 12:02 AM
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#13
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Dumbo going poop, Daddy :) Group: Members Posts: 818 Joined: 22-January 03 From: Seattle, WA USA Member No.: 182 |
QUOTE(Bleyseng @ Jun 14 2003, 09:06 PM) Korijo, I don't have any idea what the power band of your motor will look like other than with all that stroke I would think it would be at lower rev's. Depends on the cam too. Jake Raby puts in a mild cam for bus motors so all the torque is down low. For the bugs he runs those 86a combo's which moves the band up higher. Geoff (IMG:style_emoticons/default/aktion035.gif) Cam is 86. Prolly puts me right in the middle (IMG:style_emoticons/default/confused24.gif) |
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| URY914 |
Jun 15 2003, 06:56 AM
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#14
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I built the lightest 914 in the history of mankind. Group: Members Posts: 121,017 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
Bleyseng,
Did you pull the tranny apart and make this change only using stanard tools? Or do I need to get those "special tools" I see in the catalogs? Paul |
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| Bleyseng |
Jun 15 2003, 08:09 AM
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#15
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
I already had the deep dish 30mm socket from changing first gears. Other than that just a small gear puller. It wasn't a hard job at all but time consuming like assembling a engine. Putting things together and then apart, test fitting, cleaning everything.....I used Red Beard's article plus the factory manual.
I will install it in the car in the next few days. Geoff |
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| EPK |
Jun 19 2003, 09:36 PM
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#16
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Newbie Group: Members Posts: 20 Joined: 26-May 03 From: Victoria B.C Member No.: 740 |
Very interesting transmission changes, of course you are declaring these changes when you AutoX. I would think that this would put a 914 into modified class. If not I will re-read this topic and maybe next year make the change.
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| Bleyseng |
Jun 19 2003, 09:52 PM
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#17
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Its legal in the class I run. Wouldn't want to cheat...besides Chris Reale reads everything I post so he would tell!
Geoff |
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| ChrisReale |
Jun 19 2003, 10:12 PM
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#18
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Sleazy Group: Members Posts: 2,665 Joined: 20-January 03 From: San Francisco Member No.: 176 |
I would'nt tell, I'd just copy you (IMG:style_emoticons/default/laugh.gif)
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| Bleyseng |
Jun 19 2003, 11:37 PM
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#19
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
I just finished putting the rebuilt tranny in. Now all I need is a clutch cable. The old one had 2 strands left so no wonder the petal felt weird.
Drained the oil out of the old tranny and its full of sparkles (IMG:style_emoticons/default/sad.gif) The pilot shaft also has lots of play in it which doesn't bode too well. (IMG:style_emoticons/default/sad.gif) (IMG:style_emoticons/default/sad.gif) Geoff |
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| RustyWa |
Jun 19 2003, 11:45 PM
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#20
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Working Member Group: Members Posts: 610 Joined: 2-January 03 From: Kent, WA Member No.: 72 |
I just drained my tranny oil a few weeks ago and it was full of "sparkles" also. I might have something like 1000 miles on the car since I last changed the gear oil. Is this normal wear? Synchros or what?
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