Recently picked up a 99' Sierra (GMT800) regular cab short bed (RCSB) that I'm planning to put my carbureted 6.0L (LQ4) into. One of the issues us carbureted LS guys run into is transmission selection. When running a carburetor w/o a factory PCM, you cannot control a 4L60E / 4L80E electronically. I'm considering the possibility of using a powerglide with a manual valve body. I like them because they are inexpensive, easy to work on, lightweight, and have alot of aftermarket support. I'm wondering if anyone has run a powerglide in a GMT800 truck (or any full-size) and how their experience has been? Obviously would suck giving up overdrive, but seems like a better option than a TH400 to me based on weight / size / difficulty to rebuild (obviously give up the more aggressive 1st gear, but I'm okay with that). My other option would be to run a 4L80E with a plug-in that allows to shift manually. I've used these in the past on 4L60Es and it makes the shifts insanely harsh. Another downside to the 4L80E is the torque converters are super expensive (I believe cause they have lock up). I'd need a fairly aggresive torque converter 3000+ stall to match my camshaft (summit pro LS stage 4).

 

you already have the glide so use it and see if you like it.

 

4L80e or TH400 would be my pick. What is the truck used for? Dedicated track-only truck or mixed use/daily driver?

I've always thought you could build a stronger TH400 with less money vs a Powerglide. But I don't really know much about the Powerglides TBH.

A 4L80e is essentially a TH400 with overdrive and electronics.

I drive a 99 Silverado ECSB 2wd with a 5.3/4L80e 3.42 and 31.5" tires. Basically stock, cruiser/daily drive/weekender truck but I really like the transmission over the original 4L60e.

 

Powerglides are usually used in lighter vehicles than a full-size pick-up truck.

You did not say what you intended to use the truck for. For drag racing only it may work, but IMO a 3-speed trans would be a faster transmission. If truck is intended to be street driven using a powerglide and a 3000 + stall torque converter, IMO is asking for trouble. I feel that the torque converter will slip way too much and overheat the trans. This is just my opinion, but I would at the very least use a 3 speed for drag race and a 4 speed for street/strip use.

If naturally aspirated install a turbo spline input shaft, a high clutch hub and add a few more clutches in the high clutch drum and the powerglide should be strong enough to meet your needs. I don't see you making over 600hp, if that.