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

[slivel]

My Experiences:
I ran a 914 transmission in a dedicated track car for 23 years. Over time I upgraded the gear box to billet intermediate plate, steel synchros, modified gear set (AFNSY), external oil cooler, pump, and spray ports.

Heat is the death of transmissions and I was working it hard with a 3.4 liter twin plug at nearly 290 rwhp.

In 23 years I had two on-track failures and they were before the cooler and spray ports. One failure was ring and pinion, and one was 3rd gear. I did refresh the box about every 3 or four seasons depending how many events I did. A big year was 10 events.

I used 1st gear sparingly - only to get moving and loading the trailer. Most tracks involved using only gears 3,4,5.

My CV joints and axles were 100 mm CV's sourced from a 944. Direct bolt-in if you also source the trans output flange and hub flange from early 911/912. Never had a CV failure.

I used a thermo switch epoxy to the side of the case which energized a relay to turn on the cooler pump at 180 degrees F.

Sorry about the filthy condition of the parts in the photos - best I could find in my archives.



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