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

[FourBlades]

Thanks for the great replies everyone!

Seems like the 901 should last a while with the right upgrades.

Love the gear ratio chart @slivel!

I plan to run the same cooling pump and radiator that were in the car when I got it.

Adding a spray to the diff seems like an easy upgrade and maybe a couple more, like 3rd, 4th, 5th gears.

Do most people use -10 AN lines?

If I use the billet intermediate plate, do I need to reset the pinion depth? That is a big question. If not, then I think it is a no brainer to get it.

Maybe the 108mm CVs from the 930 are overkill? Maybe the 100mm CVs would be enough?

John

[Charles Freeborn]

Thanks for the great replies everyone!

Seems like the 901 should last a while with the right upgrades.

Love the gear ratio chart @slivel!

I plan to run the same cooling pump and radiator that were in the car when I got it.

Adding a spray to the diff seems like an easy upgrade and maybe a couple more, like 3rd, 4th, 5th gears.

Do most people use -10 AN lines?

If I use the billet intermediate plate, do I need to reset the pinion depth? That is a big question. If not, then I think it is a no brainer to get it.

Maybe the 108mm CVs from the 930 are overkill? Maybe the 100mm CVs would be enough?

John

In answer to the billet plate question, yes and yes. The intermediate plate takes a lot I of abuse as the thrust is directed at it. The billet upgrade is very worthwhile for that as well as having a superior (and new) int main bearing retainer. It is also wise to drill out (ideally on a milling machine) the case and use through bolts and Jet nuts as the threads in the case are also stressed.
As for gear lash set up; yes. The int plate swap is a complete tear down so all the tolerances will need to be checked and likely reset. Get used to doing this regularly. Nothing beats up gears of any kind more than excessive lash.
Traveling at the moment but will post pics of my rebuild when I get home.