Hi Can anyone tell me what size transmission my 1975 class C has? Thanks

I'm gonna guess a THM-350, maybe 375, but a quick look at the pan shape should tell you....FMI:

http://www.nastyz28.com/chevy-...n-identification.php

I'd bet a THM-400 - they were pretty much standard on the cutaway vans of that vintage.

Some small block vans came with a TH350. TH400 was an extra cost option. The pan shape will tell you, for sure.

The TH400 is tougher, but TH350 has lower 1st and 2nd gear, better suited to a small block with a load, and still plenty tough.

If you have a 350, use the lever to shift down to 2nd instead of mashing the throttle. That gas pedal kickdown is a heck of a jolt on a 350. On the TH400, 2nd is closer to high, so the jolt isn't as hard on things.

75 G30 came with TH400s.

From the GM Motor Home Chassis Service Guide (Red):

"Chevrolet motor homes are equipped with one of two different automatic transmissions, the 350C (G-Series) and the 400-475 (P-Series). Both are fully automatic units which use a three-element hydraulic torque converter."

My 76 G30 has a th400 as did my 75 Class C.

Try this thread;

https://www.barthmobile.com/eve...943946077#5943946077

Pictures and discussion of the THM400 and trans coolers.

Does anyone know what the max temperatures for a TH475 transmission is? Keep hearing conflicting numbers from other sites......?

Thanks~

Here.

Optimum operating temps are 185°-205°F. Synthetics slightly raise ATF temperature tolerance, but the clutch faces still can fail with excessive temps.

Thank you, Rusty.

Depending on the location of the trans temp sender you may get way different values.

I had the sender in the (hot) line out to the cooler, often saw 300 degrees on long hills. I found this alarming. (Not sure why they put it there) When I put the sender in the trans pan I see about 160 to 180.

I have one Hayden cooler in the trans loop. I had two but temps were too low. I do not use the cooler in the radiator.

The hot line to the cooler runs hotter but by the time the fluid returns to the pan it is at normal temp. The fluid will oxidize more quickly at the higher temps but the short duration limits the damage. Meanwhile the internal trans temps are normal, so things are good for seals and clutches.

https://www.barthmobile.com/eve...1087061/m/5943946077