Transmission or something else?

[PonyUp]

I had my tranny rebuilt and it still is not shifting properly. First it was the 14-18 MPH range. If I was moving along and car was slowing down due to a curve or turn, it would hesitate going back into gear when I accelerated. Vacuum modulator? was changed and then it did it at 36-45 MPH range. Had a filter/fluid change done and nothing bad in the pan. Up inclines or curves where acceleration is slowed and I accelerate to maintain speed. It tries to goes into gear( upshift?) but it is like something makes it stop. I have let it do that (lurch forward then go down, lurch forward then go down) 8 times, every time it does it before I gave up, just let off gas and went below 36 until I got past curve or hill. There was "slop movement" in the rear end and car has close 200,000 miles on it. So I had rear end rebuilt. Guy said he adjusted the accelerator cable? Well now it is doing the same thing between 44-55 MPH. The RPM needle goes up and down as it tries to upshift. Tranny guy put synthetic tranny fluid in. Could bad spark plugs or spark plug wire have anything to do with it? Those were all changed out 22,000 miles ago. Tranny guy said it is not the tranny. Thanks.

 

[MikeG]

It sounds like a transmission issue to me, but years ago I had some weird shifting issues that I was *sure* were the transmission. Took it to a transmission mechanic, he told me it was the coil packs! Kinda doubted him but replacing them did in fact solve the issue. No longer remember what testing procedure he used to figure that out, but rode along while he demonstrated he could make the behavior happen under certain throttle conditions. So yeah it could be something else. Wouldn't have believed it, other than it happened to my truck.

Anyway maybe this helps, maybe not. Don't really know how to test the coil packs. Or if there is a better way to test transmission. Good luck.

 

[PonyUp]

Thanks Mike G. Coil was replaced along with some other electrical components. I checked the spark plugs wires and they are in good external condition. Car runs great on a flat road at any speed. It is just when RPMs slow down on incline and I accelerate to maintain same speed or have to slow down on a incline for another driver and then try to get my speed back up. Only happening now at 45-55. Have to let foot off gas pedal and drop back to below 45 to make it stop the loop. As soon as I get to top of incline and then accelerate, it will shift fine. It has something to do with small inclines/small hills. Not good at any rate but certainly not good as I live in The Texas Hill Country and I have already put quite a bit of money into my car. Ouch.

 

[RonD]

duplicate post

 

[PonyUp]

duplicate post

I apologize if I have something wrong here. Please enlighten me.

 

[RonD]

It reads like trans issue, could be computer issue though, at 45-50mph i.e. torque converter lockup

Vacuum modulator should be the adjustable type, has hex key adjuster on it, you could try turning it a 1/4 turn one way then the other way to see if issue goes away or gets worse, remember which way you turned it, maybe mark the modulator and screw for reference before adjusting

EDIT
My post was the duplicate

 

[rusty ol ranger]

Check the vacuum line running from the engine to the modulator

 

[PonyUp]

It reads like trans issue, could be computer issue though, at 45-50mph i.e. torque converter lockup

Vacuum modulator should be the adjustable type, has hex key adjuster on it, you could try turning it a 1/4 turn one way then the other way to see if issue goes away or gets worse, remember which way you turned it, maybe mark the modulator and screw for reference before adjusting

EDIT
My post was the duplicate

Thanks. Tranny guy replaced the module and checked line right before rear end rebuild. Problem started after tranny rebuild and then an electrical "meltdown" due to the wrong alternative/harness installed prior to tranny rebuild over a year ago. Took 2 months to replace wiring, relays etc. Tranny guy replaced 2 of the solenoids and the plugin after meltdown. Weird thing is after second module replaced, the shifting issue changed gears. Thinking rear end may have been the issue. After rear end rebuild it changed gears with shifting issue again. Will ask tranny guy about torque converter and adjusting the modulator. I have a good computer from a donor Bronco and will pick up in a couple of weeks. Thanks again RonD.

 

[PonyUp]

Check the vacuum line running from the engine to the modulator

Will clarify with tranny guy. He said he did when he put second modulator in. Thanks.

 

[PonyUp]

Hopefully the end of tranny saga. I replaced spark plugs and that did help a tad but still not shifting right. Didn't get to the spark plug wires as they had to be ordered. 9 days after rear end rebuild I could feel and hear interior vibration on front right when tight turning wheels in either direction. Took to 2 shops and nothing wrong with front suspension system. Second shop diagnosed issue with noise as "clutch chatter". It went back to guy who did tranny and rear end rebuild. Clutchs were bad in new rear end part. After he put in new part, no issues just yet after 60 miles of driving.

 

[19Walt93]

Before ripping into the rear end again try adding friction modifier and doing some figure eights to work it into the clutches. We always soaked the clutches in friction modifier before installing them to avoid the customer having to break them in, I'll bet he didn't because the modifier sticks something awful.

 

[PonyUp]

Before ripping into the rear end again try adding friction modifier and doing some figure eights to work it into the clutches. We always soaked the clutches in friction modifier before installing them to avoid the customer having to break them in, I'll bet he didn't because the modifier sticks something awful.

THanks for your reply. He did put the additive in the first time and the second time. Until yesterday, car only did the shift slip thing 2 different times within 400 miles and it only "lunged" twice before kicking in when it did happen. Before this last last rear end "clutch/part replacement", it would just keep lunging until I let off gas or floored it. Yesterday, it did the "shift slip/lunge" 3 different times/places when in the 38 to 48 MPH range, going up a small incline and me attempting to maintain speed. Was so hopeful. Will ask him about the "soaking/breaking in" part today.

 

[PonyUp]

torque converter lockup

Thanks RonD. Sorry for delayed reply. I am going to ask the Tranny guy. He comes highly recommended but no human is perfect and not all new car parts actually work as expected. Hard to explain, prove something when I cannot get it mess up on command. .