What HP level requires transmission upgrades?, I have 200 HP to the wheels, what do I need? Options

[FourBlades]

I realize it is probably torque that kills a transmission, but I don't know the torque output of my engine.

I am building a 901 transmission for my IMSA 914 and wonder what upgrades it will need. I have some possible upgrades I could do now.

First, I have a set of 930 stub axles, CVs and the corresponding sway-away axles for a 914. They are stronger and the CVs are available for $80 from pelican. Downside is I have to destroy the existing rear bearings in my axles to use them, which were rebuilt by PMB.

If I have 200 HP to the wheels are the 930 CVs a necessary or worthwhile upgrade?

Second, should I upgrade to the billet intermediate plate at this HP level?

If I do, will I have to reset the pinion depth? That is something I can't do myself and would need to find a shop here in Florida that can do it. I know this is overkill for a typical 914, but with 12 inch rear tires and a 2.5L six, is this when the upgrade is worth while?

I am not adverse to starting with the 914 axles and upgrading down the road. Pulling the engine and transmission is not that time consuming. I would hate to break the smaller axles or CVs the first time at the track though.

I have a stock gearset and know there are probably better gear choices for Sebring, Daytona, etc. No idea where to start with those.

I will be running a transmission cooler to start and may move to gear set spray bar over time. I have read that the mesh point of the gears is where to aim the cool oil sprays, not sure this is correct.

I appreciate any advice people have.

John

[campbellcj]

My experience has been similar to above. My box had been built by John W at Ottos many years ago and was behind a relatively low torque 2.2 at first, then the significantly stouter 2.7. It has a 904 mainshaft, oiling mods, billet int plate, guard TBD and short gears.

By the last couple track events I did it was really shot including the R&P, several gears, synchros and various other bits. All freshened-up now including new clutch & flywheel, intermediate plate, and rebuilt diff as well but I still have no cooler on it. I actually have one in a box taken off a retired POC 914-6 racecar, but haven't pulled the trigger on the install and am not sure how much fab is entailed. It's definitely on my list as I don't want to have to rebuild that extensively again anytime soon (ever) and this car sees significant heat loads - high RPM in desert conditions.

In terms of the intermediate plate, my old one (Weltmeister) apparently had no bushings/bearings and was showing some galling, and also may have had some heat deformities, possibly was the culprit of the thing jamming in 4th prior to being replaced. The new one is bushed. Anyone have experience or thoughts on that?

[Charles Freeborn]

My experience has been similar to above. My box had been built by John W at Ottos many years ago and was behind a relatively low torque 2.2 at first, then the significantly stouter 2.7. It has a 904 mainshaft, oiling mods, billet int plate, guard TBD and short gears.

By the last couple track events I did it was really shot including the R&P, several gears, synchros and various other bits. All freshened-up now including new clutch & flywheel, intermediate plate, and rebuilt diff as well but I still have no cooler on it. I actually have one in a box taken off a retired POC 914-6 racecar, but haven't pulled the trigger on the install and am not sure how much fab is entailed. It's definitely on my list as I don't want to have to rebuild that extensively again anytime soon (ever) and this car sees significant heat loads - high RPM in desert conditions.

In terms of the intermediate plate, my old one (Weltmeister) apparently had no bushings/bearings and was showing some galling, and also may have had some heat deformities, possibly was the culprit of the thing jamming in 4th prior to being replaced. The new one is bushed. Anyone have experience or thoughts on that?

I have it on rather good authority that the Intermediate Plate made for and sold by California Motorsports is of good quality. https://californiamotorsports.net/collectio...ermediate-plate