[TailGater]

I have a 78 gmc half ton with a powerglide in it, and reverse isn't working in it.
The two forward gears work fine, and i also found out when i have the truck up on jack stands and put it into reverse both back wheels will spin forward very slowly, fluid level is good but somewhat burnt. (the previous owner tried moving the truck with next to no fluid in it and couldn't figure out why it wouldn't move at all )
It seems to me like a seal must be leaking in the valve body and some fluid is getting to the bands for 1st gear instead of reverse but I really don't know anything about auto transmissions so I'm just kinda grasping at straws on this.
If anyone has had this happen or might know what would be wrong I sure would appreciate some help

Thanks in advance!

Oh one more thing, I know this is not the original transmission, is there any way to find out what year it is? or what it might have come out of? Thanks again!

Chris

[Chazmac]

Powerglides will have forward motion when there is no load on the drivetrain due to the band in them (low gear). It has a tendency to self-energize with engine RPM when there is no other clutch applied. It probably will spin the wheels in neutral also. This is not your problem.

Several things can cause no reverse. Is the reverse clutch burnt? Moving the truck with no fluid is not a good idea as the reverse clutch WILL burn when the output shaft is spun (as in towing). No automatic likes this...

Also, was this trans rebuilt? If so, the rebuilder may have assembled the governor support/rear case area incorrectly, blocking oil flow.

Is this a transbrake trans?? If so, many of them require the solenoid to be energized when the shifter is in reverse.

In order to help I need more info.....

[TailGater]

Chazmac,
Thanks for the reply, I really don't know to much about the trucks history, I bought it last year as a project truck, the frame was cracked on one side and the guy i bought it from was planning on fixing the frame until he found out the trans was bad. I had the truck towed on a flatbed so the tow home should not have caused any further damage. I suspect that he tried moving it with no fluid in it and may have burnt the reverse band. Is there any way to check this without disassembly? Also it is not a transbrake trans.

Thanks,

Chris

[barnym17]

you will have to tear it down to check it out, the reverse clutches are at the rear of the case.but the good news is a kit does not cost much and they are easy to rebuild.

[TailGater]

So I'm pretty much looking at a rebuild then? how difficult are these things to build? I've never tore into a trans before,are there any specialty tools needed for the job? and is there anything i should consider upgrading while its all apart?
You guys are gonna be sick of my questions before i get this done lol

Thanks again,

Chris

[home brew]

You can probably get a rebuild manual with the rebuild kit you buy.