C6 Transmission Issue

[Jim and Jutta]

Sometimes after sitting for a few day/weeks the transmission doesn't want to shift until it's warmed up so I have to shift to 2nd manually which works fine. After driving it a few miles all is well, in fact as long as it doesn't sit for more than few days the issue doesn't come back again and the transmission shifts great, firm shifts right on time with no slip at all. There are no leaks and it doesn't use any fluid. The fluid in it was changed a little over a year ago.

I'm thinking something is drying up when it sits for several days/weeks allowing pressure to escape????... any recommendations on additives, solutions?

 

[TommyK]

Sounds like a stuck governor. You can try driving at a low speed and shifting from 1st to 2nd repeatedly to try and free it up. If that doesn't work you will need to remove the tailshaft to access the governor and clean it.

This is sometimes a symptom of debris in the fluid but not always. Sitting for long periods of time can do it to.

 

[marks73]

It's always a good idea to manually shift an automatic that sits for any period of time. It helps to lubricate the the clutch packs and valvebody.

 

[Totalled]

Your C6 doesn't leak when the car sits..? Are you sure it's a C6?

 

[Jim and Jutta]

Your C6 doesn't leak when the car sits..? Are you sure it's a C6?

LOL...yeah I know, amazing but not a drop.

 

[don29163]

pull the rubber hose off the modulator valve and see if trans fluid runs or drips out of it...do this before you start it up. If there is fluid in the hose, the modulator valve is bad...easy cheap fix.

 

[Jim and Jutta]

Sounds like a stuck governor. You can try driving at a low speed and shifting from 1st to 2nd repeatedly to try and free it up. If that doesn't work you will need to remove the tailshaft to access the governor and clean it.

This is sometimes a symptom of debris in the fluid but not always. Sitting for long periods of time can do it to.

Tommy, it only happens after it's been sitting for a long period of time and it does free up after it's warm, manual shifting it does free it up but next time it sits it does the same thing. I don't think it's debris in the fluid since the fluid was recently changed...but I guess it's possible.

pull the rubber hose off the modulator valve and see if trans fluid runs or drips out of it...do this before you start it up. If there is fluid in the hose, the modulator valve is bad...easy cheap fix.

Don, sounds like an easy check, I'll do it this weekend...if I can google and find where the modulator valve is.

 

[Totalled]

Passenger rear of the trans. Has vacuum hose(s) going to it.

 

[Jim and Jutta]

Passenger rear of the trans. Has vacuum hose(s) going to it.

Thanks, found it. I pulled the hose loose and yep, a small amount of transmission fluid came out, I'll stick on a new modulator valve as Don pointed out and see if that fixes the problem.

 

[will e]

Well that would be cool if it was a cheap fix.

My engine has to warm up for about 3 minutes before I drive it so it's never really a problem.