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Discussion Starter #1
Rebuilt the C6 in a Mustang recently, but having a problem. When the xsmn is cold, it shifts perfectly. As it gets warm (15-20 mins on the road), it starts to hold its gears longer and longer before upshifting, and eventually will not upshift at all unless you manually move the shift lever and force it to upshift. I have replaced the vac modulator with no improvement. Since it is apparently heat/pressure related, can anyone give me some other ideas to look at here? Thanks!
 

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6,911 Posts
im betting some clearance gets larger as it warms up
 

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10,588 Posts
This page is an example of how a trans service manual can help you diagnose your problem...it's a handy thing to have.

What happens, under moderate throttle conditions, if you leave a standing start with the trans in drive range? Compare that to a WOT start...

How does reverse engage?

Are there any bubbles in the transmission fluid when the dipstick is pulled while the engine is running?

Get back to us...
 
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Discussion Starter #4
thanks for the reply.

1. From a standing start, if its not warm, its fine. The upshifts slow as it gets hotter. Downshifts remain fine no matter what the temp.

2. Reverse works fine.

3. I will try a WOT start, but, as it doesnt have a kickdown lever, that may not be informative.

4. I will also check for bubbles and report. Thanks again!
 
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