Tranny Question Please Help!!!!!!

[DANTIP]

My '72 K-10 4x4 has an automatic transmission (TH350). The tranny shifts fine but it does not want to down-shift when the gas pedal is floored. The detent cable appears to be fully pulled-out when at full throttle but it does not kick-down to a lower gear. As I slow down (like approaching a stop) the tranny down-shifts properly. Any ideas?

[crazy4chevs]

Take the cable and pull it out all the way like you floored it and see if there is any pressure on it trying to pull back. It should have a little spring pressure at the end pulling back if not then it probably came unhooked in the trans. If this dosnt help maybee someone else can help offer more suggestions.

[crazy4chevs]

OH, forgot I believe the downshift is done by the govenor not the kickdown cable so it shouldnt affect it.

[Longhorn Man]

The cable controls the "passing gear" and also holds first and second (depending on road speed) when you have it floored. If your cable is too loose, or broken, streached, or disconnected on either end, it will not preform these functions proberly.
The govenor will force an upshift at a pre0determined RPM regardless of what gear the selector is in.

[Stout72]

I'm experiencing the exact same problem as DANTIP is. How about some more insight in correcting this problem with the TH350. I'm not so schooled in transmissions. Thanks.

[COBALT]

Both the TH350 and the TH400 have different mechanisms for inducing a downshift on acceleration (400 is electrical and 350 is mechanical) but they both work on the same principals. The TH350 uses a cable that connects to a valve pin inside the case using a cotter pin. First thing to do is check the tension on that cable. If it's loose enough to move it around then it's too loose. You may just be taking up the slack when you hit the gas.

The basics of shifting aren't too difficult. The vaccum modulator helps control upshift from 1-3 under normal acceleration using vaccuum from the intake. Similarly downshift from a specific RPM down to a stop is a similar process. When you mash the gas the detent cable is supposed to force actuation of that pin, and force the downshift. The governor uses counterweights to determine when to shift based on road speed. It has a gear that runs on the output shaft. Both have to work right for your transmission to know how your engine is performing and how fast you're going to determine when to shift and in what direction.

If the governor gear is stripped or the counterweights need attention then your normal upshifts and downshifts would be irratic and you'd know it right away. Similarly if your modulator vacuum diaphram was leaking you'd have difficulty shifting normally as well. Both are real easy to fix, but that doesn't sound like your problem.

Since the detent is probably the culprit I think everyone's right when they suggest just checking the detent cable. Heck, the cotter pin in the case may just be broke...have someone get in the cab and mash the gas with the truck OFF. Watch the cable and see how it moves....if it seems to be working ok, you may have to yank the pan to check how it's connected inside the case.