Can't swap valvebody's as the trans case casting is very different at one end of the valvebody in the TH-350C case. Pump passages area is different also, along with pump, input shaft, some other pieces.

You're going to have to go clear to the tailshaft, swap 9" output shaft and tailhousing into the TH-350 case in place of the 6" stuff.

 

thanks i figured as much just wanted to be sure

 

while im at this do u happen to have a list of the known weak hard parts in the th350
doing a lil experiment and want to swap a th350 inplace of the th400 in the car

 

Intermediate sprag assembly and outer sprag race is one, get improved sprag and hardened race. There is also a much, much better cam type sprag being sold by TCI, BTE and other transmission parts suppliers, it is a dogbone type sprag with 36 elements and similar to the TH400 34 element sprag, but you have to buy it drum and all as an assembly, around $275 last I knew but a must for over 450 HP/500TQ.

Low roller clutch sprag is another that should be replaced, the springs and roller assembly. Seems like IIRC the 700R4 piece is the upgrade for older 350's but check into that, I could be confusing that with something else.

Cut down forward clutch piston and direct clutch piston on a lathe to take one more clutch and steel for more holding power. Seems like this is also a place you can use thinner 700R4 clutches and steels to add more to each clutch pack, you'll have to do some more research on that also, as I don't remember it all anymore, been too long since I did much of it.

There is also a thicker wall sun shell to prevent cracking or stripping the spline out, don't remember the name of it (The Beast??)

 

thanks ive started collecting the parts i need , the beast sunshell is for the 700's

 

i use the 1987 up 700r4/4l60e center support with the wide sprag and 4l60e tubular steel clutches in the low and reverse clutch pack use the 350c planetarys because it will use bearings instead of thrust washers
use a clutch drum piston to allow 5 clutch plates in direct upgrade to a hd intermidate sprag race or a hd sprag and drum if funds permits also use a trans go shift kit