Bass GT3

Guy's,

I'm looking for a bit of informed knowledge from the racers here. I am currently building my 924 GTR racer, complete with 380BHP motor. Now i need to decide what gearbox to fit.
having searched extensively, there sems to be various issues with the 944/968 transaxles, and i would like to narrow down which is the better option.
The ideal box is the 944S box, as it seems to have fairly tight ratios, whereas the 944S2 is similar, but with a higher 5th. Then there is the 968 box, with narrower ratios, but this weighs 15kgs over the 944 boxes and requires major surgery to fit. So what are the respective weaknesses of these boxes??
The car weighs sub 2000lbs, but will run wide crossply slicks, 13" in the rear. Torque from the litle 2ltr won't compare to the 951 engine, but i really don't want to be blowing boxes every weekend.
Whichever box i elect shall be fitted with a Guard LSD as i currently have a Quaife ATB which is less than ideal for my racing.
So whats the considerdopinion here? s2 box? or 968 box? or 944S box??
Or is there the option to build a Frankenstein box, by combining the gearsets from one box withthe R+P of another, to overcome any inherent weakness in a particular model. also, take cost out of the equation. I am just looking for the optimal box, which is strong but has nicely stacked ratios to keep a buzzy little 2ltr spinning up to a max speed of about 150ish.
I would really appreciate your input here, as i need to decide on this as it impacts the basic build of the car if the 968 box is the choice.

Regards,

Steve

CPR

951 gearbox. period.

Bass GT3

Hi CPR.

Thanks for the reply. can you elaborate as to why? From my ratio sheet, the 951 box seems quite long legged between gears. This is not an advatage for my application. However, if this box is significantly stronger than the others, thats a major consideration

Steve

Van

951 gear box will handle the power better (read as a normal 944 box will implode if installed in a regular turbo).

If cost is your primary concern, I'd use an S2 box. If you have some money to mix and match, I'd put an S2 ring and pinion in a turbo S gear box (limited slip, oil cooler and hardened first and second gears).

If money is of no concern, I'd call Kevin Gross and have him make a custom box that is EXACTLY the ratios and strength you want.

Bass GT3

thanks Van,

Do you have a contact number or website for kevin Gross?

Thanks,

Steve

blown 944

I don't think this has been absolutely established as there have been a couple of 951 failures lately with the high HP cars.

I believe the consensus is that the S2 is stronger and the 968 is as well but may not be well suited for the power band of the larger engines.

Also it has been mentioned a few times that the 931 trans is the strongest (I may be wrong here) coming from the hybrids trans of choice for kit cars

There a re a few writeups about it one is in GeorgeD's thread including his failure

seattle951

I have a 968 LSD in my 1986 951. I had it installed by a professional mechanic. The only difficult part of the insallation was getting the speedometer to work. The 951 shift linkage had to be replaced with 968 components. I was told this step was easy but somewhat time consuming.

If you are looking for something with close ratios, this is a good choice.

Bass GT3

guy's,

Thanks for the replies. as i have a 968 box available, i might go down this route. I have a fantastic little engineering shop local to me here in the UK who do one off work for Quaife Engineering. i'm thinking that my best option is to strip the box down and have the gearset and R+P shot peened to add strength. They are also able to reharden and test the gears and can give a good indication of the max power capabilities of the gears. Although the 968 box is heavier, it's ratios are much nicer for my engine, which is the 924 turbo, not the 944. Consequently,it is a revvy motor best kept spinning as it doesn't have the natural torque of the 951 engine. My ECU also allows me to limit torque in the lower gears, so i can effectively reduce the stresses on the box off the start line and in the tight uphill corners. And an additional 15kgs in the rear would be off benefit as this is the area where most of the weight is removed from when lightening these cars.

Steve

MPD47

The 968 box doesnt require major surgery to fit. Just a different axle.

Bass GT3

Mike,

By major, i mean i need to cut out the stock 924 box cross member and fit in the 968 carrier. Not impossible by any means, but i just wanted to make sure i hadn't missed anything before i start cutting her up as non sunroof 924 shells are like hen's teeth over here..
I will also need to source the different axle, as i understand one side will carry over from the 944, and also the 968 gearchange linkage ect.

Steve

PorscheDude1

The passenger side axle is unique to the 968.

MPD47

Ah yeah, I forgot we had talked via PM about your 924. Nevermind it DOES in your case!

Bass GT3

Mike,

I am guessing that the 968 box will bolt up directly to the 944 torque tube?? And did you ever manage to take any more photo's of your set up?? Would be greatly appreciated if you have some you could mail me.
So the passenger side for you guy's is my drivers side(RHD!!) but your drivers side is a straight fit? I currently have late model 944 rear suspension fitted, icluding torsion carrier, trailing arms ect.

Thanks,

Steve

PorscheDude1

I am guessing that the 968 box will bolt up directly to the 944 torque tube??
Yes

So the passenger side for you guy's is my drivers side(RHD!!) but your drivers side is a straight fit?
Correct.

Nothing like a left hooker.

Bass GT3

Thats the problem. Mine is nothing like a left hooker!!!

Many Thanks Guys