Thread: High HP transmission mods

300 horse is fun...for a while.

wheel hop will kill a tranny at an power level. I sheared a cv shaft in half on a stock b13 being to rough with reverse. I have not encountered any wheel on my current setup but I added traction bars. the traction bars helped traction but created lots more under steer than I would like.

I'm not really abusive as a driver as some, I am careful, I've been through 2 stock b13 transmission on stock power. They just gave out 5th and 3rd on one then the other or totally let go.

Currently have a b14 transmission.

I plan on doing more motor mods, I have a b15 transmission currently.

I have a t28 off a gtir, I hope to get close to mid 3's. However I plan on taking the motor out this winter, I'm doing a rebuild and have a Marsh VVL head built coming my way. I would like to mazworx main and headstud vet head gasket.

Internals I would like to do Manley rods, cp ve pistons and Acl calico bearings so I will be ready for a bigger turbo.

These are all great ideas I was running redline 255 shock proof and half mt 90 but currently running royal purple 75/90 and 140

Welding the b15 trans would be good, but replacing and doing transmission work I have a little experience with the b13 transmissions I know it wil get expensive, I don't plan on road racing at this point although the cooler would be a good idea.


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I already have es bushing everything. So that helps has anyone done the cryo treatment. I know welding on the would require all the bearings replaced however I don't know if the modification would make that much of a different, I would removing the gear stacks and have the cases welded up right?

Just getting prepped for throwing on a t3/t4 or gt35


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Does anyone have picures of they're outter case welded up? What about making a Miko brace up?


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the problem with welding the case is it just breaks in a different spot on the tranny case. the p11 and b15 housings are stronger but the gears are marginally stronger than the b13,b14 and p10. If your looking gt35 you better start with at least a b15/p11 box. I would start collecting parts for a 6sp swap.

6 speed or go home. Seriously. Who bothers with high hp on any of the 5 speed boxes. 17 passes at the track last night with 500+whp on street tires and there was even wheel hop a couple times in 1st 2nd and 3rd and it took every lick. Ive put some serious abuse on my 6 speed trans and it just keeps taking it. No worries even on the back of my mind with it.

Given that the 6 speed swap costs a lot of money and takes quite a lot of work -- which whp threshold would you advise to make the effort and spend the money to get the 6 speed? 400whp?

I did the swap with less power than 400whp b/c I wanted the highway gas mileage.
I do plan on hitting 400whp soon though.