In very high-powered GT-Rs when launching, even with DOT R-compound road racing tires, not even drag radials, we have seen a few cases of differential case breakage. The ring gear wants to rip away from the pinion and puts tremendous stress on the cast aluminum case which flexes, making the problem worse, finally breaking. Since the differential case is part of the transmission case, the whole case is ruined which is sort of a moot point because Nissan sells no service parts, a very compelling reason not to break the diff case! Shep trans offers an optional billet diff cover made by PRL which comes with super-strong ARP bolts. This greatly reinforces this area which will give us a lot of peace of mind.
Another huge problem that we have run into before, even on road racing R35s was the differential itself wanting to crack the case and pull away from the transmission! To prevent this Sheptrans uses T1 Racew Developments Transmission brace. The T1 brace is two pieces. The first piece bolts from the top of the transmission case to loop around bolting to the differential cover.
The second piece goes from the bottom of the differential cover to the side of the transmission case. These two pieces are made of strong nickel-plated steel and will absolutely stop the differential from cracking away from the transmission and prevent the differential case itself from cracking. We would recommend these parts on any GT-R that makes decent power, drag raced or not.
With our car now having a transmission that we can launch to our heart’s desire, that can easily take our projected power level, and much more if our power goals get greedy, we can turn our attention to the engine. If your car has more power than ours, don’t fear Sheptrans has proven combinations that can reliably handle over 2800 hp and 2000 lb/ft of torque! Like our transmission, our engine build is suffering from supply chain issues that are preventing us from getting all the parts we need. Be patient, it will be interesting and worth it!
Sources
Sheptrans
Dodson Motorsport
Bulletproof Automotive
Drexler Motorsports
T1 Race Development
PRL Motorsports
7 comments
Are you sure you want to add “super-strong ARP bolts” in the blind holes machined in to the cast aluminum differential cover? Higher strength bolts means more clamp load to achieve the same stretch which in turns leads to shearing the threads in the non-serviceable transaxle. Those holes don’t look to deep so it would be a good idea to triple check the thread engagement calculations.
There is nothing wrong with that and its proven in competition.
Any significant penalty in weight or rotational inertia from the beefier gears?
It’s probably a slight penalty but when the alternative is breakage, it’s a moot point!
Is there some reason that they don’t go with straight cut gears? Seems like noise and vibration wouldn’t be a serious consideration in this application.
Personally, I kind of enjoy a bit of gear whine in a race car.
The helix of the gears is changed for more strength. Helix gears can be stronger although they do waste more power.
Best in the business plus he always helps you out with any kind of questions! Installed my SHEP stage 4+ and ready now for turbo upgrades.