Auto trans TC lock up ?
 

My TC doesn't want to stay locked in 3rd. In overdrive it locks as soon as I hit the go peddle. It seems to soon almost lugging. I can tow locked up in overdrive 65- 70 mph just fine. I come to a hill where I can't pull, the engine will lug and not unlock TC. I switch off overdrive, the engine just races, no lockup. If I drop speed to about 35-40 mph I can sometimes coax it to lockup, but it won't stay locked. Over the hill switch on overdrive again it locks again everything is fine. I want to switch the TC soon but I need to find the time and money to do it. The truck has low miles, 56k. Any ideas will be welcomed. Thanks

Well if your TC holds in OD lockup it is NOT the cause for the problems you have now!
Did you check codes? Your year will need a scanner to do it.
If that doesn't give any hint I'd go for a pressure test. (Shop manual is about 90US$ and the best thing you can buy for your truck.

HTH

AlpineRAM

I did take it to the dealer a year ago. They reflashed the computer. But they really couldn't find anything wrong. Driving on flat ground with no load. The truck drives fine unloaced except for the quick lockup in overdrive, which seems early. But I have nothing to compare it with. Shouldn't the TC lock and stay locked in 3rd?

Yes the TC should lock the same in 3rd as in OD (same rpm and same throtle position)- OD lockup can occur as soon as 40mph.

HTH

AlpineRAM

How do you unlock the TC? Can you step on the throttle? I have to switch off overdrive to release the TC. Then in 3rd it doesn't want to lock, even on the flats. Only once in awhile if I vary speed it will lock but if I give it a little throttle it releases. When I'm towing in overdrive locked up and step on the throttle I think it down shifts to third engine races, high rpm, then I let off it shifts back to overdrive then 1 to 2 seconds later locks up. It pulls fine in OD not 3rd.

Sounds like an electronic problem to me- reason is that the lockup clutch will apply and hold so the solenoid is good and there is pressure. I assume that your tranny fluid isn't burnt and is at the proper level etc.
Normal behaviour of the tranny- light to 3/4 throttle approx- OD on- will upshift from first to 4th and will lock up then. Applying more pedal eg in 4th lockup will make the tranny unlock then downshift. It won't lock up in 3rd then. If you press OD off it will have 1-3rd and will lock up in 3rd. Same rules, if you are slow and apply go pedal it should unlock or unlock and downshift.

AlpineRAM

gwatson;

I believe i have the same syptoms as you. I have a 01 with 38K, and have good shifts 1-2,
2-3 but when it should go into lockup it just wants to continue to rev until i feather the throttle and then it will shift into OD/lockup around 50mph. This happens with no load in bed and not towing. It seems the 3rd lockup is real sensative. I started a thead last week asking basically the same question. Was told to have pressure checked, but believe i might need a aftermarket torque convertor and valvebody or possibly have the pressure increased.

sound like u need 2 replace the solenoids...they may have developed internal seal leaks.

RAM2940, gwatson: To me it sounds like you possibly have a lot of noise on the APPS signal to the PCM. You can check it out with an OBD2 reader by monitoring throttle position from the PCM with the reader. If you keep your foot steady the percentage should not change. Try this while driving in the situations when you experience this lockup problems.
The pressure check should be done anyways to be shure that it's not an hydraulic issue. For a stock engine the stock tranny in good shape will not slip, so there's no need to change the TC or the VB if the rest of the tranny is OK. If there is an internal leak a VB is only a band aid. The leak will stay the same and the pump output won't change with a VB so the actual apply pressure for the clutch may still be too low even with a modded VB. A new TC with lower stall will increase your problems if you have internal leakage because the engine RPM will be lowered and therefore pump output is also lower- combine this with more torque input and you can smell the burning clutches :(
HTH

AlpineRAM

One more thing. With OD off my RPM's are 3000 at 65 MPH. Does that confirm the TC is not locked?
Thanks