Myth or not? TH400 Tranny in our trucks

[GMC JUNKIE TOO]

Just to add to the confusion gm allso put th400s in 6 cylinder trucks my 69 gmc panel truck came with a 250, t400 and 4.11 positrac factory and its a low hump. I have noticed more gmc trucks have t400s than chevys.

[GSFMECH]

All the above sounds right for the 400 turbo behind the small blocks until 69. My buddy 65streetcruiser bought a loaded 68 CST back in the 80's that came from the factory with a 327 and 400 turbo. It was a nice old truck with a wood floor in the fleetside bed. They were a dime a dozen then and we wound up junking it out.

[kwmech]

Since many of you are throwing different possibilties here is mine 69 GMC C-30, small block, low hump, and no park gear, not even on the steering column. R N D L only.

[Longhorn Man]

cab chassis? I've seen this a few times. HD truck thing.

[1969 GMC]

Originally posted by badpeanut
I don't mean to hijack the post, but there weren't ever any TH400s in the 4x4s (all automatic trucks were TH350s)?

I'm 99% sure that in '77 and up K/30 trucks, if an auto tranny was ordered, then it was the TH400. I have seen them mated to both NP203 and NP205 transfer cases.
But in 67-72, all 4x4 auto were TH350.

[butter]

Anybody heard of a turbo 375 that what was in my truck. The yoke size is in between the 350 and 400. I found out because somebody stole my orignal drive shaft. This trans was in 71 bb camper special that I bought to rob the motor and trans out of for my other project. I had never heard of this trans before.

[GSFMECH]

Yes I have heard of it, my brother had one. My book says they were offered from 72-76 and has THM375 cast into the bottom of the extension housing. My book also says they made a THM475??? used in 71 up med. duty trucks, buses and motor homes and a dead ringer for a 400, the only way to ID it is the tag. This is the one with the straight cut planetary gears. Learn something new every day. I have the book THM 400 transmission book by Ron Sessions, it's got a ton of info on identifiying them.

Mike

[Gee_Emm]

Is there such a thing as a turbo 300? I saw someone mention somewhere that they wanted to swap a th300 in but I assumed they meant 400

[kwmech]

Originally posted by butter
Anybody heard of a turbo 375 that what was in my truck. The yoke size is in between the 350 and 400. I found out because somebody stole my orignal drive shaft. This trans was in 71 bb camper special that I bought to rob the motor and trans out of for my other project. I had never heard of this trans before.

It is a 350 yoke, same splines as a 350---[27] Have the same thing in my truck, uses the smaller 1310 series u-joint at the trans then goes to the 1350 series at the diff.