Myth or not? TH400 Tranny in our trucks
 

I’ve heard may folks here claim they have a factory TH400 transmission. I have the 68 resto pack and a lot of sales literature for our series of trucks. Nowhere is there any mention of any automatics other than the Powerglide or Turbo-Hydromatic. (I presume they are talking about the TH350.)

Was the TH400 really offered in these trucks or is it a myth? Who here can prove that they have a true FACTORY TH400 equipped truck and not the just a TH350 equipped truck? Did GM differentiate between the two automatics in their literature? What was the first year of the TH400? Was it available in all Light duty trucks or just the H.D. C/20’s and C/30’s?

I’ve been wondering about this for a while.

Absolutely fact. If you had a big block (396 or 400/402) and a "Turbohydromatic", it was a TH400.

Oh, that's the designation of the TH350 and the TH400.

TH350 = TurboHydramatic for a 350cu in engine
Th400 = TurboHydramatic for a 400 (396/402) cu in engine.

:bowtie:

G.M. NEVER PUT A T-350 BEHIND A BIG BLOCK. EVERY FACTORY AUTOMATIC BEHIND A BIG BLOCK WAS A T-400. :D :D JOHN

Even without a truck you can verify this with the aluminum rivited tag on the side of the TH400 case. I have three TH400 transmissions (one in the truck which is original). All 3 of them belong to Chevy Trucks.

ckhd is right on the money.

so 68 was the first year for the TH400?

On my 68

TH400= Turbohydramatic for a 327ci engine.

Not only is it a turbo 400, but I was told by the trans rebuild guy that is the very desirable one that has the straight cut gears? I guess they were used on Motorhomes and heavy duty trucks too?

my 67 has a th400 and the 327 engine. I believe it designates the turbo 400 on the tag in the glove box

Typically it doesn't say that on the option sheet. It'll say "Turbohydromatic" or "Powerglide". The only way to be sure is to see if you still have your build sheet under the seat or behind the seat in front of the fuel tank. I don't know for sure if there was a TH400 for a chevy truck in 67. The only TH400s I've seen are for '69 and up.

TH400s were originally produced in 1965. The issue is just whether or not they made it into our trucks by 67.

Here is what my Option sheet shows but I have a BB.
The 72 restoration guide shows 2 auto trans under that option ,one for the BB and another for without BB .?
There is also a 10 dollar difference in price .

it is elementary my dear watson, indeed there was a factory th400 setup for our trucks. I know this due to the fact that the cab floors had a larger tranny "hump" so when your ordering carpets say you had the factory th350. I said that I had a 400, not knowing there was a difference, and recieved the wrong carpet kit.

I think 1966 was the first year for th400 in pickups. That was the first year for 327's and they were equipped with them. I bought one that year. John

high hump, low hump is not 100% correct... this truck had a low hump and TH400 behind a 350. 72 Cheyenne that sacrificed itself so others could live.....

I can put this myth to sleep. GM didnt make the t350 until the end of 1968. So 1969 was the first year for those. Everything before that had the turbo 400 or powerglide.

From my understanding, this is correct.

Thanks for the info. I've always wondered about the TH350 vs TH400 option in these trucks.

So.... In conclusion,

The TH350 came out AFTER the TH400 in 69?

Any "Turboautomatics" in 67-68 (and before) were TH400's?

Glove box option sheets don't list the TH350 or TH400 as different options just the "Turbohydromatic"option?

GENERALLY Turboautomatics after 68 were either TH 350 if mated to a SB/I6 and a TH400 if Mated to a BB?

I just always found it odd that in 68 anyway they go to great lenghs to explain availability of various manual trannys with various engines but they only mention ONE turbohydromatic transmission. I always thought the TH350 came first.

a little known fact, the th400 takes around 35-40 hp more than the th350 to turn the pump.

Jay

Some early to mid year 69s also recieved the TH400 in a half-ton with lwo hump cab, my 69 has factory TH400, and I've seen several others.

69 3/4 ton Custom Camper with 350/400 here

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

I think the figures I have heard is more like 15hp.

My burb is a low hump turbo 400.

THM400's came out in 1964 and were changed very slightly for 1965. THM350's came out in 1969, don't know what month.

I have never seen a small block?th400 truck with the high hump. The only time I have seen high humps over TH400s was big block trucks, and now 2 V-6 trucks, but only in 1/2 ton. (Finally able to explain the high hump in my GMC)