C6 transmission not going into reverse.
Trailering
Joined: May 2024
Posts: 20
Likes: 8
From: Downey, CA
On a C6 for reverse the low/reverse and high/reverse (direct) clutches are applied. See if you have manual low 1 with engine braking. It feels different than 1st gear in D. In low or 1 it should feel like a manual trans vehicle in 1st gear when you let of. That's the engine braking. If you have that and it shifts into 3rd in D position, obviously, your clutches are good. Also smell the fluid. If a clutch is bad fluid will smell burned and be black. If everything is good so far the you have a valve body issue.Block the wheels. Pull the pan and valve body and find the one for reverse that is stuck. You'll probably have to open the valve body to do this. You need at least one gasket maybe some o-rings. You can get some wet dry extra fine sandpaper and clean up the crud on the valve. Check torque spec's. usually in inch pounds for reassembly. Don't guess here.
Mountain Pass
Joined: Mar 2017
Posts: 181
Likes: 18
i had a trans shop take care of mine and while the trans came out fine, they didn’t tighten down the cross member.
Trailering
Joined: May 2024
Posts: 20
Likes: 8
From: Downey, CA
A couple things I forgot in my other reply. Check the shifter linkage to make sure it's adjusted properly. I erred when I said to check the fluid. If the fluid is good it doesn't mean your in the clear and might only be a problem in the valve body. Bad seals in low/rev. clutch would cause no reverse and wouldn't make the fluid smell burned, brown or black. Do the road test in all the gears especially Low 1 and second 2 to check for engine braking. Then in D check for a shift into high 3rd gear.
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Mountain Pass
Joined: Feb 2011
Posts: 186
Likes: 13
A couple things I forgot in my other reply. Check the shifter linkage to make sure it's adjusted properly. I erred when I said to check the fluid. If the fluid is good it doesn't mean your in the clear and might only be a problem in the valve body. Bad seals in low/rev. clutch would cause no reverse and wouldn't make the fluid smell burned, brown or black. Do the road test in all the gears especially Low 1 and second 2 to check for engine braking. Then in D check for a shift into high 3rd gear.
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Mountain Pass
Joined: Feb 2011
Posts: 186
Likes: 13
Yeah I like to do as much as I can myself, especially since this truck is more of a project/weekend cruiser compared to my other vehicles.
Trailering
Joined: May 2024
Posts: 20
Likes: 8
From: Downey, CA
Like if the shifter doesn't want to easily go into park or stay in park. Many years ago mine jump into reverse for some unknown reason but never done it again. I've seen cars neutral creep then eventually jump into drive because worn bushings and maladjustment. The shift valve will be just far enough towards D to let a little bit of fluid leak past it. Eventually enough does and it applies the forward clutch and away it goes! If it goes into park and doesn't want to jump out and goes into Low 1 and doesn't want to jump out then you're there. The shift collar can also wear and cause problems. Linkage can get so sloppy from worn parts then someone will come along and "adjust" it. Many times you can have a problem with the valve body and the rest of the trans. is fine. I'd guess that most people in this forum have never had an auto trans. completely disassembled and are not fully aware how they work. The clearances in a valve body are extremely tight. Any varnish, rust or corrosion on a valve can make it stick. Even incorrect torque on valve body bolts or valve body to case bolts can cause a problem. But I'm getting too far ahead here.
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