Thread: High HP transmission mods

Hey folks,

I know there are a many an sr making 500hp+ on the forum, however our motors love the boost, but it's paired with a crippling weakness in our transmissions, besides going 6 speed and custom everything hell, what are some things one could get away with on a low mile b15 transmission?

Twin disk clutch set up is a must??
Enforce transmission casing? Tig all the gaps?
Bracketry?

Suggestions? Ideas? Personal experiences are all welcome. I know it can be done.

-Josh


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Twins is not necessary even at 500hp. We have one in our bracket car and seems like everytime we leave on the 2step another bites the dust. Most we can do is heat treat gears, weld the case for cracks and strap down the motor as best as possible. Good tranny oil can also help.

Yeah definately, cryo treat the gears? I have ES bushings for motor mounts. Just weld the case up solid


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Valvoline 85w140 either conventional or durablend. Trust me when I say it will make the gears last 10 times longer. Ive yet to break a 5 speed trans when using it and I was on a twin disk for a bit and an act extreme w/ 6 puck unsprung disk over 460whp and over 500 on high boost. Went from breaking gears every 3 months to same stack lasting 9 months and never breaking.

Make the power with revs and low boost to keep the torque low and you should be all set. Rev that thing out to 10.5k or so and you'll make 500 HP that won't destroy transmissions/clutches/halfshafts. Keep the torque curve flat at around 250 ft/lbs. and you're done.

I'm doing a marsh vvl head, I feel that might help lower the torque curve


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Gears: Cryotreat, Shot Peening, REM help the gears without a doubt.

Case: Tig it up - You can make aluminum fillers to weld in. It is VERY IMPORTANT to bolt the case down when welding so it does not tweak in shape. Also will likely require replacement of the trans shaft bearings.

Clutch Disc: Cryo & Shot the disc before the friction material is added. This will will help prevent stripping out the splines on the clutch disc & input shaft. I Sprung Hub is ideal (in my opinion) to help extend trans life as it helps to absorb the shock.

Suspension: Lower control arm bracing, uprated bushing

Engine: Solid engine mounts - Ideally the NISMO or JWT if you can find (Both discontinued years ago)


Good luck.

I would say that the way you drive/launch will be a huge factor in how long your trans will last

Completely. This ties in with what Ben said. Shift on the right curve and it will be butter

boost by gear is your friend and preload

have to understand big hp isnt going to break the trans its the tq coming out the hole and wheel hop also