C6 shifting problem. Need advice
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C6 shifting problem. Need advice
My 1983 C6 2WD is only shifting into first and second, but not third? What causes something like this? I got the truck with bad headgaskets and finally got it on the road tonight and noticed a shifting problem now. Any help would be appreciated.
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floor it and see how fast it will run, you won't blow it up, but it may start shifting with some rough treatment. and sometimes, if you put it in neutral, it will shift to 3rd. can you hear-feel every click? park, reverse, neutral, 3,2,1? there should be 5 clicks, put it in the 3rd click no matter what the little thingy on the dash says and then run the **** outta it for a little while. it may start acting fine. just a thought
Mountain Pass
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Assuming you have reverse, the hard parts of trans are working. If the modulator was not working, the 1,2 shift would be delayed. Make sure you have proper vaccum at the modulator (maybe the vaccum is low) and that the shifter is properly adjusted.
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I have the proper fluid level. I have no leaks that are visible. I do not have the kick-down rod in place. It was not fitting properly, so I just left it off. I get all the clicks, and I have reverse, neutral and 1 and 2 gear. I will get out there and check the modulator. How much vacuum should I be getting there?
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Mountain Pass
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The modulator receives its signal from the Vacuum Regulator Valve located on the side of the Injection pump. Compare the vacuum on the vacuum pump side of the VRV (engine running) with the vacuum at the modulator at idle they should be close. (Must be at least 13 in.) When you apply throttle the vacuum to the modulator should drop . The VRV is adjustable. Also make sure the modulator is not leaking Trans fluid and can hold a vacuum.
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Is it possible for the kick down mechanism in the tranny to not work? I moved the lever all the way in woth directions, and no difference. Still no third gear. I will check the modulator. I was told by a tranny guy that 3rd gear is the weak point in the C6. Maybe third gear is bad? How can I tell what kind if modulator I have "green stipe" or "purple Stripe"?
Mountain Pass
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High gear in a C6 uses the forward clutch. This is used in all fwd. gears. It also uses the reverse/high clutch. If the truck will back up that clutch must be working. If you have first and second the forward clutch must work. Try reverse with the brakes on to see if the reverse/high slips. if the engine revs high maybe that cluch is slipping.
The modulator will have that colour stripe on the body. Don
The modulator will have that colour stripe on the body. Don
Last edited by Don Senkow; Nov 8, 2004 at 04:01 PM.
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Great. Will try that. I will also try to adjust or check the VRV. Not sure how, but will look at it tonight. Also, I will try to put the kick down rod back in place and see where things line up. Maybe the kick down sensor is stuck in the 2nd gear possition. I moved it all the way front, and all the way back, with no difference. Maybe I will try to make it fit correctly and install it rather than leaving it off.(it hits the IP a bit). Maybe some bending would help that problem.
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I was under the impression that the kickdown mechanism can keep it in 2 gear? I got this truck and it had head gasket problems, so I took it appart to fix that. I never drove it before now, so I don't know what happened. I am trying to dignose the issues without knowing history. Now the engine runs good, and I just need to figure out tthe tranny problem. Have not had a chance to work on it again. I will need to check vaccuum and modulator, next.