Izzone

One of my gearboxes has a 7:31 R&P....last weekend after appx 50 hours it decided to give up

1st I decided to install a cooler, hopefully add some life

2nd I need to find a replacement. Guard and Albins make a 8:35 that gives close to the final ratio of a 7:31. 8:31 is not an option since I do not want to re-stack the box

Does anyone have experience with aftermarket R&P and the durability vs OEM?

amso3

Randy

I have the 915 oil cooler set up on the later euro trans if you want to go that direction. I also have the 74 RSR setup which adds a pump in the nose piece and an oil squirter tube over the gear sets and r/p and has fittings to add an external cooler.

MUSSBERGER

Was heat the reason for the failure?

Izzone

I would assume it just timed out....I wasn't running a cooler. Went for power in second gear exiting the keyhole at mid ohio and it let go. thankfully only pinion was broke the rest of the gearbox is fine.

Ordered the WEVO bottom outlet cover....and am going to pump the oil back to the pinion and try to keep it cooler

Have a used 7:31 spare I can put in the box, but if I can verify a 8:35 aftermarket is stronger I will probably buy one

Good thing I have a spare box with a 8:31 and a similar output

pu911rsr

What size engine are you running, the 7:31 are known to be a weak link in high torque/hp motors. I'd call one the 915 tranny experts and ask them. I think the best thing you could do would be to swap out R&P fairly frequently - not an inexpensive solution. if the aftermarket stuff has stroner more fatigue resistant materials that may be a solution.
Phil

Toby Pennycuff

After the fixed 3rd gear dropped a tooth as I was prepping for TWS last year, I decide to add an oil cooler to the transmission along with new 2nd and 3rd gears. Hayden (Wevo) offers a GREAT setup with the sump plate and Weldon pump and associated plumbing. He also offers an enhanced oil spray bar that oils all four gears in the transmission housing as well as the pinion where it meshes with the ring gear. I added an external Setrab cooler along with a SPAL puller fan. Almost done with the installation. Also running Swepco 201.

As for the differential,, I think both Guard and OS/Giken offer LSD's for the 915. Guard should also have the 7:31 R/P. If not, check with Steve Weiner at Rennsport Systems in Portland. He was able to get stock gears for me and should be able to get a R/P in 7:31. Good luck.

Toby

Izzone

Im buying 1/2 the WEVO set up...race shop says spray bar isn't needed just cool oil to pinion gear

running Quaife LSD in both transmissions

Ill call Steve Monday...good idea

Izzone

engine is a 3.0L

never been on a engine dyno just bolted some parts together ...but its somewhere north of 350 HP, max rev of 8,200 rpm

im hoping someone on rennlist has experience with the 8:35 stuff...one more tooth should make it stronger than a 7:31....assuming the metal is created equal

Matt Romanowski

Before you put the box back together, send the ring and pinion, all the gears, bearings, and races to http://www.cryosciencetechnologies.com/. Tell Mike I sent you. Have it all cryo treated and REM polished. You'll lose around 40* F without doing anything else. If you are curious or don't believe it, email me and I'll send you the data.

car_slave

I believe that kind of pinion failure is the result of flexing under heavy torque. I studied up not this after I ran into problems with my Range Rover diff. The solutions are thicker crown wheels or the addition of a backing plate behind the crown where it meets the pinion - no idea if this is possible to do on your gearbox.
Here's a good reference for this mod:
http://www.ashcroft-transmissions.co...f-pegging.html

blue911rsr

I have had some of those failures in multiple 915 trannys with big motors . Want happens is side cover flexes what cover do you run? Flex is greater with 7 : 31 than 8 : 35 I have run8 : 35 for long time now with out problems and also do have a new old stock one for sale

Izzone

What brand of 8:35 do you run

I have a thick aluminum side cover that says 915 on it, no idea on brand

I'm happy with the life of the pinion I got..just looking for something to last longer

blue911rsr

I run albins and oe race part both seem to be fine with out problems . The cover you have appears to be albins as well which would be fine do you have main case insert from wevo if not that would be nice upgrade also one piece bearing retainer a must for big bore car hope this helps

GTgears

A couple of comments. Do your homework. Quaife doesn't manufacture lsds. They make torque biasing differentials. There is a difference and many technical discussions on this board about the technical and functional differences between the two.

Number 2. We make an 8:35 cwp because it is stronger than a 7:31. Porsche had the 8:35 homologated because it was stronger. Francis Tuthill runs ours exclusively as do Bernard Munster and Romain Dumas. I have them manufactured by Ricardo, the same Ricardo who makes the 991 Cup gearbox. I was working then 5 years before Porsche Motorsports was. Yep, it is more expensive than an Albins version. But then Albins made all of Powerhaus' gears. They went bankrupt in 2008.

GT won 4 national titles last year. And has been around for 25 years. You get what you pay for.

Ps. Google "gotta get a giken" if you head to head to head Giken versus GT. Every Cayman in CTSSC fighting for the title next week runs a GT. 2 seconds a lap worth $500 when the championship is on the line. He'll, Foss and Mossing even jumped chassis and didn't touch how I tuned that LSD

Regards

Matt@guard

Izzone

Thanks Matt, that's what I was looking for

Zotz Racing takes care of my car....was going to have Ron call you this week to discuss

You are correct...quaife is not a lsd lol, but it is what is in the box

Another question anyone have experience with the wevo / ap 915 clutch kit?