Auto trans,

[hugger6933]

There is a current thread running about a 71 Custom Camper and what trans it has. Most answers are it is a 350 trans, I replied that I would thought the 3/4 tons had TH400 in them. Now is a TH350 a trans that would be in the 3/4 ton? What about a one ton? I have a C30 and am wanting to go auto instead of the four speed in the floor. Could that truck[ with a small block]have a TH350 too? I think I have a couple extra 350's around but only one 400 and it is in my Big block GMC. I also have a ton of 4L60E but not one 4L80E right now that doesn't need a build[and the stand alone for them is more $$$$. Jim

[jocko]

the auto transmissions were primarily by motor size, but it's evolved over the years. TH350 was primarily paired to sbc and TH400 was paired to bbc. Exception to this rule is in the prior generation of trucks - when TH400 first came out, it could be had in a 66 with a 327. Have seen a few 66 Custom Campers with 327s and ORIGINAL TH400s floating around lately.

[hugger6933]

Jocko, would that be primarily due to the year thing? wasn't the TH350 out in like 69? I may be way wrong on that year it just seemed like it came out later than the 400 witch was like 64 wasn't it?
I know in the later years all of the trucks i owned that were 3/4 ton or 1 ton they had the TH 400 so I assumed[you know what happens when you assume] that it was always that way with the 350 trans in the 1/2 tons and the heavier trucks got the 400 trans. But I'm only going off of what I owned I had a 82 3/4 ton traded to me and a 84 and I built a bunch of 88 89 and that body trucks that had 400's in them. I even had a 4.3 truck with out air and a th 400 in it from the factory.

[FirstOwner69]

My 69 3/4 ton CST with a 350 has a TH400. It has all the required equipment for the Custom Camper nameplate option, but it is not a "Custom Camper". This is just 1 piece of evidence that at least some 3/4 tons with 350s had TH400s. Maybe it was dependent on GVWR. Mine has the maximum 3/4 ton GVWR of 7500#.

[jocko]

Originally Posted by hugger6933

Jocko, would that be primarily due to the year thing? wasn't the TH350 out in like 69? I may be way wrong on that year it just seemed like it came out later than the 400 witch was like 64 wasn't it?
I know in the later years all of the trucks i owned that were 3/4 ton or 1 ton they had the TH 400 so I assumed[you know what happens when you assume] that it was always that way with the 350 trans in the 1/2 tons and the heavier trucks got the 400 trans. But I'm only going off of what I owned I had a 82 3/4 ton traded to me and a 84 and I built a bunch of 88 89 and that body trucks that had 400's in them. I even had a 4.3 truck with out air and a th 400 in it from the factory.

correct - TH400 only until the TH350 came out, regardless of engine size (I guess I could've worded that more clearly the first time, sorry). Wasn't sure when TH350 came out, but discussion above makes sense 69-70 or so. Had seen recent examples where they were paired as early as 66 in trucks (with small block, the only choice in 66). TH400 was available in cars as early as 65. Anyhoo - I'm most interested in toomuchstuff's last comment - 1 tons with TH400 but also TH400 in a C20 with a 350 engine. That's the case I would not have expected from the factory, but I learn something new every day. I learned this lesson in a strange way - so, perhaps that is why I remembered it as I did. Bought a 71 C20 Cheyenne Super - I expected it to have a TH400, and the seller indeed stated it was a TH400 (cl long distance buy, big risk!). When the semi was bringin it my way, the trans konked out and the driver couldn't even get the other vehicles off enroute - so, he rolled it off the back of the truck and left it for dead on the side of the road somewhere in WA state. So, seller had to retrieve it (I was in CA), I wasn't too happy at this point. Anyway, then he bragged about his quick fix with a fully rebuilt TH350 he installed. I reminded him I bought it with the original TH400 and he changed his story - TH350 original and that is what konked out and got tossed aside. Anyway, long story short, still bought it and did some research. Everything I could find pointed to TH350 more likely in a 3/4 ton with sbc. Sure WISH it had had the TH400.... But I digress.. Oh, and it is true that all K's had TH350 only - no TH400s in 4x4s until the next gen trucks.

[Bigdav160]

From the information on the GM Heritage site, the Powerglide and Turbo Hydramatic were both available, as an option, in 2WD with small and big blocks. This would have been the TH400

4WD shows manual transmission only until 1970 when the NP205 started being used. That would also be the start of the TH350 in the trucks.

Funny, Corvettes and Z28 Camaros didn't use a TH350 until around 1976.

[FirstOwner69]

Originally Posted by Bigdav160

From the information on the GM Heritage site, the Powerglide and Turbo Hydramatic were both available, as an option, in 2WD with small and big blocks. This would have been the TH400

4WD shows manual transmission only until 1970 when the NP205 started being used. That would also be the start of the TH350 in the trucks.

Funny, Corvettes and Z28 Camaros didn't use a TH350 until around 1976.

The 1969 Service Manual and Overhaul Manual both have sections dealing with the TH350. Therefore, it must have been available at least as early as 1969.

[too much stuff]

Most 69s and older i have seen were either the powerglide or 400. I think the rpo code is just for a turbo hyromatic which could be a 350 or 400. My 72 one ton cheyenne camper is a 350 engine and 400 trans if i remember correctly.

[Keith Seymore]

Originally Posted by too much stuff

Most 69s and older i have seen were either the powerglide or 400. I think the rpo code is just for a turbo hyromatic which could be a 350 or 400. My 72 one ton cheyenne camper is a 350 engine and 400 trans if i remember correctly.

The "merchandised" RPO (MX1) is just for a turbo hydromatic, regardless of size.

The "non-merchandised" RPO is then driven by the engineering specifications (not selected by the customer) which then differentiates between a TH350 or TH400 (M40).

Another example: let's say a customer wants a three on the tree. The salesman would choose RPO MM3 (the merchandised RPO) and the engineering specifications would then drive the correct trans based on other powertrain and gvw considerations, either non merchandised RPO M62 or M64.

Just to finish this thought: it becomes moot when only one transmission is offered. For example - for a three speed + overdrive manual transmission the merchandised code is MM7, but there is only one choice (RPO MY6, which was the New Process A833 trans).

K

[picklito]

I personally know of a 69 C20 with 350 engine and 400 trans. I don't think that's unusual, but I remember crawling under a potential purchase C20 that had 350/350. I was surprised, but it was original.