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Discussion Starter #1
I have a C6 from a '72 mustang behind a 351C engine in my '70 coupe. Problem is the transmission has a good hard shift into reverse and also it goes into gear in drive when started cold. Once temp comes up to 190 and you place the shifter into park and then back to drive, nothing. Reverse always works. Rev it up and it just slips, nothing. Trans was rebuilt and I removed and cleaned the valvebody, worked for a bit but now is the same. Could this be dirt? Is there a way of working the dirt out of the trans in the car?
 

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Low and reverse servo piston may need to be replaced. This part does not have a removable seal, not routinely replaced in an overhaul.
 
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??? C-6 has 1 servo, C-4 has 2. C-6 servo is second gear only. I suspect the forward clutch pack has excessive clearance. If there's a tranny problem with a C-6... I've had it. That's what I said when I went to a C-4 in my drag car. Sounds like a re-build. It's cheap & easy. If you want to tackle it yourself I have a ton of info & pics.
 

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Sounds like one of the problems I had with my C6.We found , even though it was suspose to be "newly rebuilt" the steel clutches had rusted and rust was stuck to the fiber clutches. replaced the clutch pack, fixed it...
 

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Try shifting it down to manual low or manual 2nd and report what you find; if either of those two work, try driving a bit in those gears and lightly accelerate and decelerate, noting vehicle/engine reaction.

Try running the same tests, including a drive range test, with the car up on stands so the wheels can spin freely. Note the results.

What, if any, debris did you see in the pan when removing it to clean valve body?

Do you have a transmission service manual? Do you feel you have the requisite skills to perform diagnostics on the trans?

Get back to us...
 
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Discussion Starter #7
Is there a difference between some C6 forward clutch packs. ie. the number of clutch discs. Did '72 C-6 transmissions behind 351C-CJ have more discs. If so could this be why the trany does not go in gear once warmed up?
 
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Discussion Starter #8
There are several C-6 variants with from 3 to 6 forward clutches but that won't matter if the clearance was set right to begin with.
 
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