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High HP L28et transmission choice?


JacktheRiffer

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The T5 won't live. At 300ft-lbs of input torque they start breaking quickly, and be honest-you aren't going to baby it around. Not all the time, anyway.

 

The FS5W71C transmission will live at 300ft-lbs input torque for a while, but it will wear out quickly.

 

The FS5W71E transmission has some upgrades and can be strengthened further from stock, but again, limited life at the power you're talking about. When upgraded internally with stronger, bigger bearings (a lot of complicated machining required and I'll never do it again) I hope to get decent life out of mine.

 

The FS5R30A is the go-to here for strong transmissions. It's a lot of work and they're a bitch to rebuild, but once assembled properly and fitted to the car, it will last a long time under severe service.

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The T5 won't live. At 300ft-lbs of input torque they start breaking quickly, and be honest-you aren't going to baby it around. Not all the time, anyway.

 

It's not the 300ft/lbs that kills the transmission, it's the intense inertia energy release that happens when engine rpm is pulled down quickly. Even a 250hp engine can easily generate a 700+ft/lb torque spike at the input shaft, all it takes is an aggressive clutch coupled with sufficient traction.

 

A T5 can easily live at 400whp, you just need to pay attention to what clutch is in front of it. If clutch capacity is < 500ft/lbs or so, you will probably be fine. The T5 input shaft i have here on my desk has a minor dia of around .760" in the spline area. I'm not sure what alloy it is, but a treated 8620 shaft of that size would have a yield strength of about 1000ft/lbs. Mustang Cobra clutches are a pretty good match for a T5, lots of Mustangs running low 11's to high 10's 1/4's with a T5 using that clutch...they have a 10.5" organic disc and a PP load of around 2124lbs, shouldn't be too hard to come up with something close that will fit. Bottom line is you don't have to be afraid to run slicks if you choose the right clutch.

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The E is the 5 speed that was fitted behind the VG30E and VG33ER in (some) Nissan Frontier pickup trucks, the only changes are internal. All of the gear teeth are wider and the midplate is thicker, which allowed me to fit almost double the bearings into mine.

 

Yes, the E will bolt up in the same method. You can not modify an "A" bellhousing to fit, you must use a "B" or "C" bellhousing (both exist for the L6)

 

I would definitely be on the lookout for a diesel transmission, as they had cast steel front bearing plates instead of the alloy ones that the rest of the transmissions got. They are not spectacularly easy to find these days.

 

If you ask me, I'd not run anything less than a Z32 transmission if I was going to upgrade. It's not that much extra work and it's pretty much on par with all the other transmissions as far as "work needed to make it fit" so best to do it once and call it a day.

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