Transmission for a Turbochevy

I haven't owned a car or truck with a particularly powerful engine.

I think my next project should change that.

GMT-800 trucks with the 4.8 are plentiful, and E85 is available here.

With the appropriate turbocharger, I should be able to make 700 lbs*ft at 7500 RPM, with adequate charge air and water cooling.

What manual transmission would be able to tolerate that much torque and spin that fast, and also stand up to fairly light service for a half-ton (full bed frequently, 1000-3000# trailer a dozen times per year)?

With the weight of the vehicle, plus your power requirements, and intended usage, you are likely going to be looking at a pricey, beefy T56 variant, like a T56 Magnum or a Rockland Standard Gear "Tranzilla".

Magnum t56.

or 4l80e auto and enjoy not shifting thus keeping your turbo spooled at all times.

In most cases where people ask for budget transmission for gen III/IV engines I always back down to the early four speed boxes, but in this case I think the turbo would hate the wide spreads at those boost levels, though I don't have experience in that.

I'm with patrick. A well build 4L80E with a manual valvebody will get what you want I think.

Also the th400 as the 4180 is a 400 with overdrive . It will take huge power and more importantly torque.

what about a TR6060? A used on from a Gen 5 or 6 Camaro.

In reply to Gearheadotaku :

It's about the same expense to buy a new one.

We don't bother with trying to source used ones.

In reply to chaparral : I think that depends more on you than the transmission.  

How do you intend to use the truck? Wide open throttle under heavy loads?  OK, buy a new T56 hope it lasts, which if you’re driving wide open hauling heavy loads it’s likely to longer than other component parts will.  

If you once in a while go full throttle just to make smoke out of your tires.  You’ll probably be OK  ( Assuming the transmission is properly warmed up first etc ).   

It’s the engine I’d worry about.  You see pump  grade E85 is almost never 85% ethanol usually closer to 50% and sometimes as low as 31%. To add to the issue pump gasoline base stock  the 15% or more gas that E85 is mixed with varies in octane rating a lot.  Since ethanol is 114 octane and they don’t market the octane of E85  they can use pretty low octane base stock 

In reply to frenchy 

E85 is great but pump stuff is a big question mark. 

If you want 700 hp in a engine out of the Junkyard use the stuff from race gas suppliers. If you use E85 from the pumps play it safe. Use less timing, richer mixture, less boost.  Don’t keep your foot in it until pieces come out.   

And/or use an ECU that senses ethanol content. 

NV5600.  You'll never need the granny first or the really low reverse, but it is the go-to for beefy.

NV4500 is a 1/2-ton or light 3/4 ton trans with more workable ratios, but I think 700 torques will kill it pretty quick if you hook up the rubber.

T56 and Mag6060 have pretty terrible ratios for truck use.  You'll need at least 4.56 rear to be able to use it.  Think of it this way:  a 4L60E with 3.08 rear has the same basic final drive ratio spread as a T56 with 4.10s.  So add taller truck tires and the fact that you want to use it as a truck, and 4.56 will be pretty much bare minimum.  Balancing a driveshaft to 4000 rpms isn't easy or cheap.  Plus, even the beefiest T56s and Magnums like to give up the ghost somewhere around 600 torques.

If you don't need all the gears (or the nice shifting feel), go cheap and put in an SM465.  4-speed granny, but iron case and reliable as dirt.

So, 1100hp right? 750tq @ 7500 rpm...

Ancient history but still relevant.

I would do the th400 or 4l80.