Transmission trouble? 700R4

[Scotty.92]

Alright guys, I am having a little bit of trouble with my truck. It has to do with when I am just cruising down the highway. The problem exists with what RPM I am doing when cruising the highway in OD. What happens is that on some days my truck will rev at around 2/2.1k doing 70, and other days it likes to go at around 1700/1800 rpm doing 70. It does it some days, I would say it revs up higher more often than it does lower revs. I notice my check engine light comes on after usually 10-15 minutes of driving (Not sure how long it takes to come on, but comes on after a little bit of driving. Either in town or highway.) I have not checked the code yet because it goes off after I shut the vehicle off, and doesn`t come on until after driving a little while. I know OD works because I can shift it into and out on the highway.

The transmission had been replaced by previous owner (Not sure how many miles, if new or used) because OD went out of it. Was thinking that the torque converter was not locking up. Whenever I go on the highway next I was going to check if the lock up was working by lightly accelerating and start to brake slightly. I heard your rpm should go up because the converter goes out of lock up by around 300 rpm.

I am not sure if this has anything to do with it as well, but sometimes driving around town or highway. Mostly in town, you can hear a drivetrain noise. This also sometimes happens and sometimes doesn`t. I changed the rear end oil in fall and it was real dark looking. It`s an open diff so shouldn`t have required any special oil. It s filled to the top of fill plug. It makes an annoying humming noise, and does not make an increase in sound relating to speed or rpm.

*With the torque not locking, I heard it could be of 2 problems. The brake switch, and a TCC I believe it was*

Any help is very appreciated!!

 

[Scrufdog]

yeah, if the solenoid isnt locking up, its either to solenoid or the brake switch. It's usually the solenoid screwing up. You need to check the code, this will help.

 

[Scotty.92]

Went for a drive today on the highway; when I was going 105 I slightly accelerated and hit the brakes for a moment. The T.C had not been locked up, but after I did this it had locked in. On my way back it was not locked and tried but did not get it to lock. Any ideas as this helps any?

I will try to remember the code next time. IIRC, you have to turn off the vehicle and turn the key to run. I think the truck erases the code after you shut down though. Can you check the code when it is running with the paperclip trick? Or have to shut it off?

 

[Scrufdog]

i seem to remember pulling codes while running with no problems

 

[Scotty.92]

I had found the code I got was 11, that was with truck running/MIL on dash.
Right after when I turned it off, and turned key back to run, it flashed 12.

Not sure whats going on, I am sure the code goes off when I turn ignition off.

 

[Scrufdog]

Thats annoying. The next step is either hooking up live data monitoring or manually checking the brake switch and tcc solenoid. The brake switch itself generally has 2 circuits in it, one for the light and one for the solenoid.

 

[Scotty.92]

How do I check the brake switch - would you be referring to back-probing the brake switch and checking voltage with a multimeter? If so, what wire do I check and what voltage should be seen? I will look around on google to see what I can find, and probably look a wiring diagram and see if I can see the wire going to the TCC. I know my brake lights work, but also know they may still work if it doesn`t work anymore too. Thanks,

 

[Scotty.92]

Brought the truck to school and ran the snap on scanner on the truck and found code 32. It showed for the EGR system, and we got looking. The little hose front the EGR was broken and so we fixed it. MIL has not came on yet so thinking that was the problem.