94 K1500 shifting hard

[acewelderman]

I had a bunch of work done recently, New heads & a hot chip .I noticed the trans reving a bit more than usual & I wrote it off as the new chip must be making it rev then shift harder.1600 miles later its starting to intensify,From a stop it revs to 3000 rpm then shifts,same for 3rd & 4th.It dosnt slip.Trans is full & cooler is clear,I am going to throw a filter & oil cng on it this wk end.Just seams a bit wierd the way its reving .I have a th400 in my other truck & if you keep it in low 1 itwill rev for a few then shift to 2nd & 3rd.(some kind of govoner thing I think)Basicly what my 94 is doing but I keep the shifter in od.Any ideas???Hoping filter will save the day!!

[Cadillakin'98]

I believe GM built in a some kind of safety deal that makes the tranny automatically shift into 2nd at a certain RPM, regardless of where the shifter is (even if put in 1st). But I think thats the only safety thing built into the trannys. Back to your problem however, is it possible that part of the vacuum advance (?) on the throttle body may have come loose and/or not fuctioning properly? When you start it up, does it rev a little higher than normal? Maybe something was missed when it was getting put back together. 've done it, and seen many others do it; pros and rookies. Happens to the best of us ya know. If that isn't the answer, only other thing I can think of depends on if any work was done to the throttle body assembly. If work was done on the TB, what exactly was done?

[2000CAYukon]

Make sure the TPS is installed correctly. Check for the correct voltage at idle and WOT using a scan tool or probe.

//2000CAYukon

[acewelderman]

No we didnt work on the tb BUT it does rev a bit higher when cold!!I will go ck for leaks right now.I also didnt muck w the tps but it may also be suspect cuz it did rev up & down a little on the way to work this mrning.THANX I will post what I find.

[2000CAYukon]

The TPS is used by the PCM to control shifts. Since you had new heads put on, the intake must have been removed and the TPS disconnected. It is possible that it moved when the wires were reconnected.

//2000CAYukon

[acewelderman]

Yeah your right!But it ran normal for 1000+miles & never missed a beat!I looked for vac leaks & found none.Im leaning to the tps I just dont know why it would go bad.Its acting just like my th400 would if you disconected the modulater & ran it thru the gears.