Math lesson: 3.6 +915 = $$$$$

[tshebib]

I gambled and lost. I was hoping to get the season out of my stock tranny on the track but looks like I'll be upgrading mid season. This is a picture of a piece of my 2nd gear. I'll be getting the retainer and side-plate upgrade from our host but where should I look for a new set of teeth. I would like to put a second gear set from a 930 (much beefier and a little taller)
Any thoughts??
Tom

[Dodge Man]

Is it an early 915 with 7:31 R&P or later 915 with 8:31 R&P. To set a benchmark, I have an 86 915 and it was slightly stressed with an OEM Euro 3.2 so it came with a cooler for the Autobahn. A RUF or G50 conversion is a lot of work & $$$$. However, replacing gears is expensive too. A racing 3.6 is a heavy load for a 915. Best of luck.

[Sboxin]

We have had good service from CMS
California Motorsports - Porsche transmissions, transaxles, gears, differentials, parts, service, manufacturing

Give Roger a call -- he is very helpful.
They have bins of used trans parts.
They just rebuilt a 915 for our 3.8L 911SC race car.

There is probably someone closer geographically to you.

Matt Monson at Guard in Colorado makes really nice gears and parts too.

Are you doing your own work or a shop??

Regards,

[tshebib]

My Good friend Larry is doing the work on it. he called me this morning with the good news that everything else inside is in good shape----got lucky (he already did a rebuild on the tranny 4 years ago).
I just got off the phone with Mat from Guard Transmission. He was very helpful with deciding on the gear ratio. I'm going with 1.65:1 which is a little taller than the stock 1.8:1. This should keep me in the power band going uphill from 2nd to 3rd at our local track. Thanks Mat. I also ordered the one piece bearing retainer and heavy duty side cover and gasket kit. I already have an external oil cooler on the tranny. Hopefully we'll have everything back together for the mid Aug. DE..... as long as customs doesn't delay things.

[Matt Monson]

You're welcome.

Regards,

Matt

[gtihop]

3.6 + 915= That's why they made Visa!

[175K911]

I don't know, I know several folks with nicely built 3.6's bolted up to 915s in track cars that haven't had problems. But they also don't bang gears and run good Swepco fluid which gets changed annually. And have tranny coolers

You'll like the new 2nd gear if you've got some fast 2nd gear turns. I run a 20:32 2nd (1.6) in my 915 and I use it a lot at many of the tracks I run. On the plus side it's good for close to 82 mph with the 7200 redline I used to run with the old engine, and the rpm drop from 2nd to 3rd is very close which is especially nice in close competition. Down side in racing is that I'm too far down the power band for most rolling starts where the pace is usually just 45-50mph to the green flag. But I've run this gear ratio in the past 3 911's I've owned and am quite happy.

[Matt Monson]

Originally Posted by 175K911

I don't know, I know several folks with nicely built 3.6's bolted up to 915s in track cars that haven't had problems. But they also don't bang gears and run good Swepco fluid which gets changed annually. And have tranny coolers

It's not a question of if, but when. You put enough race hours on a 915 and you'll blow either 2nd or 3rd. Ask the PRC Spec911 guys in NorCal. They only run 3.2's and they buy a lot of 2nds and 3rds. Enough of them that I started manufacturing stock ratios for them because class rules require no ratio changes.

Also, annual gear oil service is too long an interval if you are doing more than a couple of events. I recommend changing the oil every 4-6 weekends.

Regards,

Matt

[Joe Bob]

Mine went as well, the addition of the WEVO intermediate retaining plate was a worthwhile upgrade.

[Joe Bob]

Welcome to Windrush Evolutions - WEVO - Porsche Products

[175K911]

Originally Posted by Matt Monson

It's not a question of if, but when. You put enough race hours on a 915 and you'll blow either 2nd or 3rd. Ask the PRC Spec911 guys in NorCal. They only run 3.2's and they buy a lot of 2nds and 3rds. Enough of them that I started manufacturing stock ratios for them because class rules require no ratio changes.

Also, annual gear oil service is too long an interval if you are doing more than a couple of events. I recommend changing the oil every 4-6 weekends.

Regards,

Matt

No doubt Matt. My annual fluid change was aimed at the DE folks who only do 4 or 5 weekends a year. I dump my 210 after 5 or 6 weekends, depending on the track, if one of my friends "borrows" my 911 at a DE a few times, or if I get bored between events. Gotta protect the Guard diff and the expensive gears in there.