I have been searching the threads all day on here and other sites for some time. This site seems to have more traffic and some pretty good insite so I'll post here.

C6 attached to a 460 w/ 78000 miles in a 1980 motorhome (I think they call it a long cone or something to that affect). Anyhow, I noticed about a year ago that the tranny wasn't shifting unless I let off the gas pedal. Did some researching and checked for vaccum, changed the modulator, hose, and changed the fluids & filter. No difference - kept driving it this year but would really like to get this squared away before taking the motorhome on a longer trip. The fluid did not have any metal and didn't smell burnt (from my nose). I checked the kick down lever and it didn't seem stuck.

I'm not a mechanic so bear with me.

1. If I was to have a shop rebuild it - what would I be looking at generally (I know it depends on location, blah, blah) but generally speaking?
2. If I was to replace it with another used one from a private party, is a C6 on a 460 interchangeable? Is a 2wd different than a 4x4 C6? Would my nose cone just transfer over?

I was thinking valve body is stuck or something but I couldn't really tell you where it's even located inside. I'm sure I'm best to just take it to a shop or find another one and try and swap them......

I appreciate your toughts.

 

nose cone = tail housing

 

Not an expert but have to say it sounds like a vacuum problem. With engine at idle, pull the rubber vacuum pipe off of the vacuum modulator at the transmission, you should hear the engine stumble if vacuum is OK. Put your finger the end of the rubber pipe and the engine should idle good again and it should feel like your finger is being sucked into the pipe. If that is good then it may be a sticking valve in the trans.
You cannot switch tailshaft housings without swapping the tailshaft also, this means a complete teardown of both transmissions. It would be easier to rebuild the one you have I would think. However the problem you have should not need a rebuild.
Hopefully some of the experts will give an opinion soon.

 

That sounds like a vacuum problem.

As was mentioned check for vacuum at the modulator.
The KD rod should also have a small return spring on it.

 

Should I measure the pressure with a tool or just know that there's lots of vacuum? I'll doublecheck on the spring..... I replaced the vacuum hose and know there's vacuum but no idea how much.

 

The vacuum modulator is adjustable, pull the hose off and with a little flat head screw driver adjust the screw out, start with a quarter to half turn at a time. If I remember right out will help it shift sooner and in will make the shift longer. There are different color strips on the modulators for different applications so you may want to try a different color.