Porsche transaxle

I am considering using a Porsche g/box as Renault boxes as rare in N.A. I have noticed references to G50 and 915 boxes in previous posts. What are the differences and which one is better? Also what is involved with flipping the ring and pinion gear if that is required?

Trevor,

The G50 is a later model gear. It is considered to be much stronger than the
915.
As far as modification, only the vent and
drain need to be reversed.
I have a G50 with a Quaife limited slip,
behind a 351W of about 500HP. I have done
serious "testing" of the gearbox, and it
hasn't skipped a beat.

Bill

Bill,

Thanks for the info. I guess I'll have to come clean. I'm planning to build a bookend for my GT40, namely a Porsche 906. This is turning out to be a much bigger job than I first thought since getting hold of authentic body sections is proving very difficult. If anyone out there knows of a source I would be grateful.

I was planning to use a 911 motor, but need to reverse location; ie engine in front of transaxle so not inverting the tranny but flipping the r and p would save a lot of work as long as flipping diff wasn't too big a job.
If anyone has done something like this before I would be interested in hearing from them.

Trevor,

There was a 906 replica on the www.mecanicimport.com website a while back.
I'm not sure if it is still available,
or how accurate it really is. The MKIV
replica that they had wasn't too accurate,
but the 906 might be worth a look.

Bill

[ October 30, 2002: Message edited by: Bill Bayard ]

[ October 30, 2002: Message edited by: Bill Bayard ]

[ October 30, 2002: Message edited by: Bill Bayard ]

[ October 30, 2002: Message edited by: Bill Bayard ]

Great input. Thanks guys. A 915 tranny it is then. I guess the old Porsche 914s back in the 60's and early 70's must have run something similar and some of them were modified to run 6 cylinder motors (914-6).

The G50 is stronger but the 915 would be better if your going to use a porsche motor. The 915 will handle anything it can put out short of twin turbos.

The factory torque specs (VERY conservative) are
915---- 237ft.lbs.
G50---- 300ft.lbs.

typically the 915 is good to about 350hp and 350ft.lbs torque, while the G50 goes to almost 500.

The 915 can flip the ring gear for reverse operation. The G50 cannot and has to be run upside down.

The 915 weighs about 100lbs., the G50 about 125lbs. The 915 is lighter and smaller and costs about 30 to 40 percent less.

Both are available with factory LSD, which usually adds quite a bit to the price.

'89 and earlier are the best years for the G50 if your going to run a V8. No bolt on gear reduction starter is available for '90 and later, and the stock starter won't turn a built V8. You can modify the later G50's to accept the pre '89 A.M. gear reduction starter, unless you do it yourself it's about a 500.00 machining operation.

Another thing to look out for with the later G50's is some come with an extended mount out the back which won't fit within the GT40 body. This can be removed but again its another machining operation.

[ November 05, 2002: Message edited by: Kalun D ]