my 86 w/ 149k on the clock runs great when cold, when warm the transmission won't upshift and the rpm will be 3000 at 30 mph! any ideas, i don't want to drop alot of $ into a 21 yr old car, but she does look and drive great, (other than this problem).
ps if i come to a stop, put the car in park and then drive, it will upshift to a higher gear for a few seconds and then downshifts and won't upshift again!!

The external part that tells the trans when to shift is the bowden cable. It's operated by the throttle cable. Perhaps something has gone wrong there.

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2012 E350
2006 Callaway SC560