[123pugsy]

The RV TH400 has some kind of drum parking brake on it. Not sure if the extension housing and output shaft are the same as a car/truck unit.

 

[Paulz]

Didn't some of the RV Th400s have straight cut gear sets?

 

[RWENUTS]

Go with the turbo 350.
The t400 eats up about 30 hp more to the rear wheels.
The rv might be a turbo 475. I think that’s the straight cut gear trans.

 

[BadWally]

A turbohydramatic 400 from a motorhome is a heavy duty trans. It may have a drum emergency brake on the output yoke. This was cost cutting measure by Gm to not have to put cables to the brake on the dual wheel rearend. The case should have "HD" cast into the bellhousing area. These have straiight cut gears sets which are stronger however make a noticible whining noise. They also have increased fluid capacity due to and deep pans, some on bigger vehicles have extra cooler lines on the back of the trans. They have modified shift points to hold second gear for pulling on long hills/inclines. The clutch packs may also have short pistons for additional clutches for high gear. They are a super strong unit, however Motorhomes were primarily used in summer months and possible pulling a trailer, which means lots of abuse and heat. .
Depending on who owned the motorhome and if it was cared for and maintained, I would have no problem using one of these units behind a 350. Check the fluid and filter, a clear indication of condition. Most likely the last transmission you will ever have to use. It will probably out live you. But hey, Just an opinion, to me reliability and toughness is of primary importance. Good luck on your project!

 

[Mudless]

Thanks everyone! I think I'll go with the T350.

 

[cerial]

Didn't some of the RV Th400s have straight cut gear sets?

Yea. Easy to check