My truck has a little 3 position toggle on the column that shifts it out of lockup (about 500rpm at 70 mpg difference). Even though the switch is 3 positions it only seems to do that one tning. First question is am i right about what that switch does?

Second question is: I have an intermittent problem when traveling in last gear the trans will shift in and out of what I think is lockup and even try to shift down a gear. I know the TPS was replaced recently but does that sound like the culprit.

Also, even when it's not misbehaving which it only does occasionally when I tap the break it will shift out of lockup. Is that normal.

I am hoping that I don't have some sort of electrical nightmare to deal with.

Thank you for your help.

 

Is the toggle factory? Or was it installed by someone else? Mine just has a pushbutton on the dash that disables O/D, still get TCC lockup though.

Need an answer to the first question before I can answer the second one.

Yep. When you hit the brake, it should disengage TCC.

Welcome to DF!

 

I doubt that it is factory but have no way of knowing. I do have the button that drops it out of overdrive like you do. The toggle drops the rpm only slightly and is very useful when pulling but I don't know anything about it.

 

If it's maintaining torque converter lock-up in third with no problems, then I would say that it is in the switch or wiring that was added.

If not, then it may be the lock-up solenoid, or the OD piston seals are starting to leak by in the trans. I would say more likely than not,that the OD clutches are starting to slip,giving you the up and down in rpms if it's happening under load.

 

It is shifting in and out of lockup and sometimes even tries to shift down a gear. It is very intermittent. Will go 100s of miles without doing it.

 

I think the toggle switch was installed by a previous owner. I would have a look at how it is wired. I suspect that some of the connections might be spotty......

 

http://www.tstproducts.com/Torque%20...p%20Switch.pdf

 

I am sorry I am late in arriving to this conversation, but I just found this forum via search for TCC's and TCM, after I posted this similar problem in another forum.

I am also having this same exact problem, with the exception of the pickup trying to downshift at times, and my pickup going 100's of miles without cycling in and out of lockup.

I am having issues with my transmission going in and out of lockup. I was cruising at about 60MPH about 3 months ago, with no load, without the cruise control on and I felt the accelerator pedal get lighter, (like a spring broke - I did check and I cannot tell if a spring broke as I cannot see very well around the linkage) and at the same time the transmission came out of lockup and then went back into lockup a few seconds later. Over the period of about 50 more miles it got worse really fast, now at speeds over 60 MPH it will slip in and out of lockup about every 5 - 10 seconds without fail. I have had problems with shifting when I first bought the pickup about 6 yrs ago where one of the seals was slipping to the point that it would not go into third or reverse and would take high RPM's to get it to go into second. I fixed this with a Lucas re-conditioner additive that a friend had told me about, and this IMMEDIATELY fixed the problem and the transmission has worked like new since then, until this problem. A shop was the one that told me the seals were worn and would cost more than $4k to rebuild.

This is on a 1995 2500 HD. I have changed the fluid several times since I bought the pickup and it is still red and does not smell burnt each time it is changed.

I am sure it is unlocking rather than slipping, is it is not a slipping feeling, it clearly unlocks, the RPM's immediately raise about 200, and then the trans locks back up and the RPM's quickly go back down about 200 RPM. It also only happens once you get to about 60 MPH or higher, no sooner, I have verified this several times.

 

Replace the throttle position sensor.

 

I checked the TPS and according to specs it is working. .78 volts at idle to 3.8 volts full throttle. Any other ideas? I know I am late but life has been financially strained and busy. Thanks for advise.