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TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale


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amcco220
New User

Dec 15, 2013, 1:53 PM

Post #1 of 4 (2563 views)
TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale Sign In

I recently bought a 1978 Chevy C10 4x4 “Heavy 1/2 ton” 350 V8 Turbo 400
“Less that 2,000 miles on crate motor and trans re-build” according to the sign in the window. Paid $3100 cash. Of course, about a month after I bought it, the transmission blew out.

Now, I hadn’t been driving it too hard, just a few camping trips and used it to move. Probably only put another 500 miles on it. This truck is my hunting/camping/firewood truck, not my daily commuter. I do want it to keep it for a while and maybe eventually put some larger tires on it and a cap. So I want it burly/heavy duty, like it supposed to be.

I hired a “mobile mechanic.” He came over and diagnosed the problem. He recommended we drop the tranny and bring it to a transmission shop, have them rebuild it, and then we put it back in at my house. Sounds good, but I had to diversify my options.

So, I went on Craigslist and I found a guy who was parting out a late-80s 2wd Chevy van, the engine from which he had put into his 80-something Chevy truck. Turns out we shared the same profession, so I dont think he ****ed me over. But who knows? It is craigslist after all. I bought a working turbo 400 + torque converter for $250 from this guy.

Anyhoo, the mobile mechanic and I dropped the transmission ONLY TO DISCOVER that when the truck was rebuilt they put a TH350 in it instead of a 400. The 350 looked like it had recently been rebuilt (or at least spray painted). My craigslist 400, however, was too long (by about 3 inches) to just be plopped in the truck and have me good to go.

Now here’s my dilemma, do I:
1) sell off the craigslist 400 turbo and bring the 350 into a transmission shop and have it rebuilt again, or
2) Do I have the driveshaft modified and buy the necessary parts to have my truck accept a 400 (from a 2wd) and plop in my craigslist tranny?

My main concerns are
1) the dubious nature of a craigslist auto part, and
2) did the 350 blow out because it was inadequate for the make & model of my tuck?


DanD
Veteran / Moderator
DanD profile image

Dec 15, 2013, 2:12 PM

Post #2 of 4 (2547 views)
Re: TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale Sign In

Short of you being an animal driving this truck the 350 is more then enough transmission for this vehicle.
You are all set up for the 350 and you're thinking of putting an unproven trans in; I think is a mistake. Tell the re-builder what you intend to do with the truck and don't cheap out on the internals for the build.

Dan.

Canadian "EH"






nickwarner
Veteran / Moderator
nickwarner profile image

Dec 15, 2013, 2:39 PM

Post #3 of 4 (2541 views)
Re: TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale Sign In

With Dan here. You got hosed on the truck, but if you have the TH-350 rebuilt at least you know what you have. Properly built these can take a hell of a thrashing. Your rebuilder can recommend some good aftermarket parts such as clutch kits and valve body upgrades to suit your intended use and make it worth your money spent. For the uses you want to use it for you picked the right truck for sure. I used to have one myself and they were built up pretty heavy and take a lot of abuse.

You'd have to modify the driveshaft to install the TH-400 that might not be a good unit. Lot of hot rodders build up TH-400s because of the heavier components in them, so I don't see you having an issue selling it and getting back some or all of your loss in buying it. Let a good rebuilder work his magic on the TH-350 and you'll be happy.


amcco220
New User

Dec 15, 2013, 3:24 PM

Post #4 of 4 (2533 views)
Re: TH 350 vs 400 turbo for my ’78 Chevy C10 Scottsdale Sign In

Awesome, I appreciate the responses, guys.

Yeah, I've read the TH350 is a pretty burly transmission in its own right, but then every write-up of the 400 mentions that is heavier duty than the 350. I agree that its a gamble to install this unproven transmission, but I just dont know the capabilities of the 350 vs 400 and all of my motor-head acquaintences and friends just didn't know enough about these older trucks and/or their Ford guys or what have you to give me a solid opinion on what I should do.

Yes, I kinda got hose on the truck. $3k for 35yo truck was a bit steep, but I was super happy with its performance when it was working. I took it up some jeep trails that defeated our work trucks (newer F250 w/ off road packages; I work for the USFS) couldnt get up in 4x4... and I didnt even have to shift out of 2wd! Also, it came with an 8000lbs winch and a gun rack, so it was already a pretty a nice mountain truck.






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