Ok so ive heard alot about the 350 turbo and i think im saying it right the turbo 400. What i would like to know is what is the main differance in the two trans since if my understanding is correct they are both 3 speeds. also just for fun would a 2 speed power glide fit into and 3gen and why would you want too?

The TH350 and TH400 have very little in common other than they're both 3 speed GM transmissions.

Length is different
Output shaft size is different
Gear ratios are different
TH400 uses a center support which makes it a lot stronger

A powerglide fits very easily. Although GM put them into many cars, by today's standard, you want at least a 3 speed for street driving. A powerglide is a good transmission for drag racing. It's light, uses up very little HP and with a few modifications, it can withstand a lot of HP. With only 2 gears, there's only one shift point.

the TH350 has a low/reverse roller clutch support actually.
I've provided a pic so stephen can see what a heavy duty one for the TH350 looks like. If you notice it is a suppport that is held in just like the th400 with a snapring. There is no bolt that goes through it because it doesn't feed second gear like the th400. I like this aftermarket support in the th350 because it grabs another set of lugs in the case making the th350 much better, and as a benefit the upgraded support houses the wide sprag just like a 700r4! I consider it a must for performance builds-I just can't understand why hardly anyone but me knows that it exists-and the larger than me companies don't utilize it -I've seen too many th350 cases go bad because this part is overlooked that it makes me sick.

Where do you buy the heavy duty roller clutches?

they are supplied to me from Transtar Industries. they are online and supply parts to the rebuilders at wholesale prices. most are will call only though if you talk directly to a salesman he'll probably ship one to you if you whip out your credit card. another source might be "bulk parts". they carry a lot of parts aftermarket and stock. hope that helps

let me get this right typically the sprag goes bad in a th350. so they put a turbo 400 sprag n and they can hold a decent amount. im getting one built that way should hold 500 hp or more. i guess

it's not the sprag that is the problem it is the transmission case. a updated support is offered for the th350 that makes it as strong as a th400. personally I like the th350, but most people request the th400/I run the th400 faster than stephen-9.2's at 146 ha. 434 stroker 70 camaro, 330 shot, small block beating all over the big block

It's not that simple. To use the TH400 36 element sprag, you need an aftermarket clutch hub. The sprag and drum kit are around $320. Not all TH400's use the 36 element sprag. They went to a weaker sprag somewhere in the late 70's or early 80's. Even the 4L80E uses the weaker sprag but it's easier to upgrade a TH400 just by finding an older version and using the early clutch hub.

yes the 36 element is the cream of the crop in a th400, but the one that I use is still a 16 element and still pushes the car fine. Most people blow out the sprag in the water box by not doing a burnout correctly. If you're scared don't upshift in the box and the sprag won't be affected. here's a pic of the 36 in a th400