Early planning options on transaxle

Hello,
early planning of build and curious as to what are the mostly used transaxle for the gt40? my engine would most likely be s 427 stacked. Ive searched and found good things on the 930 4speed as far as strength and durability. I spoke with fran a few weeks back and even he had mentioned it. Thoughts and/or other options. HP goal would be 600whp min.
thanks
joe
 
The trade off here is simply bragging rights vs drivability. 600 rwhp will mean a BIG cam. One will which will make the engine a bit of a handful below 2000 rpm. And you are unlikely to get that power down on street tires.
 

Chris Kouba

Supporter
Then you'd probably be better off with a 302/331 (~350 bhp) with Webers for show.
FWIW, that's what I have and that's what I do and it's a lovely combination (302, 345 hp/345 tq). Actually, not the Webers, but I think it's a great combo. It feels like I'm taking a racehorse to a carousel.
 
JOE,
HAVE HAD A CHANCE TO RIDE IN A GT40 WITH 450 HP? 600 REAR WHEEL WILL NEVER HOOK UP. IT TAKES A LOT OF MONEY TO MAKE 600 HP AT THE REAR WHEELS.
I HAVE 470 HP AND 450 FT LB TQ AT THE MOTOR. MORE THAN ENOUGH POWER FOR SUCH A LIGHT CAR.

JUST MY 2 CENTS
 
JOE,
HAVE HAD A CHANCE TO RIDE IN A GT40 WITH 450 HP? 600 REAR WHEEL WILL NEVER HOOK UP. IT TAKES A LOT OF MONEY TO MAKE 600 HP AT THE REAR WHEELS.
I HAVE 470 HP AND 450 FT LB TQ AT THE MOTOR. MORE THAN ENOUGH POWER FOR SUCH A LIGHT CAR.

JUST MY 2 CENTS
No,I’ve never even sat in one lol.Agreed but I have a sickness with overpowered as my last build is a 700+hp ff cobra On a mild tune. id like to be in the range of 550-600hp.
 
The trade off here is simply bragging rights vs drivability. 600 rwhp will mean a BIG cam. One will which will make the engine a bit of a handful below 2000 rpm. And you are unlikely to get that power down on street tires.
agreed and I really don’t want to run a vacuum pump at idle. Is it true the 930 transaxle is capable of the hp thought? I read the gears are strong and thick compared to others?
 

Howard Jones

Supporter
Call California Motorsports and talk to them about a custom-built 930. Be sure to tell them your HP requirements.

My advice is to hold power to 500. I really think 400 would be much better but you want 600 so I think you would completely discount my advice if I told you that. Be prepared to spend twice the cost of your motor for the rest of the power train at 600 hp. Race quality everything.

I would also recommend a Quaife torque biasing differential, max power 935 CV's, M300 stub axles, and driveshafts as well as a multidisk clutch rated 1.5 times your torque output.

You will need to have a good think about wheel sizes and the availability of tires that will not just turn to snot with that much torque.

My guess is you will be north of $50K for the whole power unit by the time you get it to work.

Will a 930 break? Yes. 600hp will break any streetcar transaxle including a 930 if you push it hard enough. It's the stub shafts, CV's and axles that I would be worried about if you put tires with enough grip in them to work with that much power. Maybe run shitty tires and just use them as a fuse.
 
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Mike Pass

Supporter
The UK based Ultima GTR has 720 hp and uses a Porsche G50. However it uses wide 19" and 20" wheels. It holds some world records for 0 -100-0. It is also unofficially the fastest car round the Top Gear track

Some transmission chat here from the Ultima forum that may be of interest.
Or more is more......

Cheers
Mike
 
A bit out of left field for this discussion, but an indication of what can break... we have a saloon series here in NZ that started out with Richmond 4speed ( Super T10 for older folks), these were fitted with a Pifitzner (spl) straight cut dog engagement kit and later moved to a Jerico straight cut dog box ( 4 spd ), engines were ~ 480hp max and car runs on ~ 10" wide slicks. I had a couple of cars/owners that were getting me to rebuild trans etc, Ive never seen so much damage to Jericos etc, some due to driver abuse, you could actually see the taper wear pattern on the gears from the main trans case twisting torsionally on down shifts etc. By comparison the trans in the TVR has been in use for 16/17 years and still OK and shift dogs look as good as the day it was fitted. I guess what Im saying is a lot of trans failure is from abuse and some drivers can break anything... you decide which camp you belong to.
 

Eddy McClements

Supporter
See here:-


Particularly from 4:05...

Harris "What was the most difficult component to make last 24 hours?"
Norbert Singer (thinks) "Ach...it's the gearbox". Then goes on to explain the challenges of endurance racing.

And if you're talking about Group C-levels of power, you're going to need to drive like Ickx and Bell....not like Ken Block!
 

Eddy McClements

Supporter
Oh...and I understand that you can retro-fit a GT3 gearbox oil pump into a G50, but I don't know whether this still applies when the gearbox has been inverted for mid-engined uses.

Eddy (closet P-car fan).
 

Julian

Lifetime Supporter
I have an Ultima with 600HP hooked up to a G50 that has seen a lot of track use, never any issue; Howard's advice is solid, my G50 was built with billet side plates, internal oil spray bars, upgraded diff, side shift conversion etc. and was a $16k investment in 2004 dollars.
 

Howard Jones

Supporter
Listen to Jac! Jac is always right! Really................he is.

I used a 125cc motocross bike to run some 4-hour enduros a long time ago. Me and a buddy won a couple of those in an everything, 125 - open bikes, in run what you brung, free for all event. Anyway later on another guy, I shared the bike with broke the gearbox in the first 30 min stint. DNFed that weekend. We chalked it up to a bad gear. 3rd had the dogs sheared off. So a couple of weeks later we did another race only I ran the first 40 min stint. All was well and we were in the top 5 and in contact with the lead. The other guy takes over and in exactly 30 min.......................ya you guessed it...........ruined 3rd and 4th this time.

Oh, and in the end, they separated the 125's from the rest..................it wasn't power, it was weight and # of fuel stops, that pissed them off.

Mario Andretti calls it mechanical sympathy. Some guys will break anything you hand them, others never break anything. I call it "drive it like it's your money"

There's no real answer to this question. It's really about how much you have to spend and what you what the car to represent to you. I say do what you want. At least when it's done you won't regret not going for it. After all, it's your money!
 
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