Turbo Hydramatic-400 Transmission Question

[Christopher R.]

Does anyone (Joe Lucia?) know the number of output splines (26 or 32) on a Turbo Hydro 400 transmission? I believe the mating driveshaft yoke part number is 3930827.

[Joe L.]

Re: Turbo Hydramatic-400 Transmission Question

Chris-----

All THM-400 were 32 spline output. GM #3930827 is the part number for the output yoke. This piece also is applicable to most 71-77 manual trans applications on Corvettes.

[Christopher R.]

Re: Turbo Hydramatic-400 Transmission Question

You're a mind reader, in addition to a parts guru. That was exactly why I asked. I believe I have such a '71-'77 Corvette manual transmission and front driveshaft yoke in my C1.

I have a vibration in the driveline. Thinking it was U-joints, I replaced them recently. The front U-joint takes a Spicer 5-3022X conversion U-joint. When I put the driveshaft back in, I remember thinking that the yoke did not go in very far. Most of it stuck out. I know that C1 yokes are longer than passenger car ones. So I thought that was the problem. I was going to buy the longer Muncie yoke made for C1s, but I believe that yoke is 26 spline.

It seems that somebody makes conversion yokes for C1s for Muncies with 26 splines. And the stock T10s with 16 splines. But I've never heard of a long yoke with 32 splines. Any suggestions?

[Joe L.]

Re: Turbo Hydramatic-400 Transmission Question

chris-----

There may be a truck-application THM-400 yoke that's longer. However, I'm not very familiar with truck parts appications

[Christopher R.]

Re: Turbo Hydramatic-400 Transmission Question

I thought the transmission was a Muncie. But the casting number on the main case is 3925656. I can't identify that.

I thought the transmission was out of a 1975 Camaro, but the casting date seems to be "Cnn1". (Where "n" = number.)

I'm trying to understand transmission outputs. It seems they come in 16, 26, and 32 spline counts.

I know all transmissions are the same length, but it seems Corvettes have longer yokes.

I know there are long yokes for at least Corvette applications for 16 and 26 spline counts. But what about 32?

If a 32 spline output transmission was used on a Corvette, what was the corresponding yoke part number?

[Joe L.]

Re: Turbo Hydramatic-400 Transmission Question

Chris----

The transmission that you describe is a later "Muncie" with a cast iron case. These were, basically, a slightly revised version of the Saginaw transmission used in the late 60s-early 70s for lower performance applications. These transmissions were used in most, if not all, L-48 Corvettes during 78-79.

The 32 spline output shafts were used on all 71-77 Corvettes with manual trans, most 71-76 Corvette with auto trans, except those few 76s equipped with the THM 350.

The "oddballs" are the cars equipped with the THM 350s and these "Muncie" manual transmissions.

[Christopher R.]

Re: Turbo Hydramatic-400 Transmission Question

"The transmission that you describe is a later "Muncie" with a cast iron case. These were, basically, a slightly revised version of the Saginaw transmission used in the late 60s-early 70s for lower performance applications. These transmissions were used in most, if not all, L-48 Corvettes during 78-79."

Do you know the spline count on the output shaft of this transmission?

"The 32 spline output shafts were used on all 71-77 Corvettes with manual trans, most 71-76 Corvette with auto trans, except those few 76s equipped with the THM 350."

Do you know if the yokes for these came in 2 different versions - one long one for Corvettes, and a shorter one for passenger cars?

[John H.]

Re: Turbo Hydramatic-400 Transmission Question

Chris -

There are several "standard" length 32-spline Corvette yokes ('71-'74 M20, '71-'72 M22, '74-'81 Super T-10, and TH-400, etc.), but I'm not aware of any C1-type "long" 32-spline yokes - just the 16 and 26.