Vedalkin

96 cherokee se 4.0 4x4

I spent about an hour searching and didn't really find any definitive answers, so I thought I would throw this issue at ya.

Doesn't happen all the time, but it is happening more frequently. It drops out of overdrive(well tc lockup), however, if I push my pedal down about half way it goes back into overdrive. As soon as I let back up on the pedal, the tc drops of lockup. Weird..

Several years ago I had replaced the TC solenoid(not fun). But it had just stopped going into OD completely. This week I replaced the TPS. No change.

I have read about it possibly being the temp sensor, or the brake switch, the ECM, NSS... But short of throwing parts at it, any ideas?

Seems to run fine until good and warmed up. So I assumed it was temperature related. Then on the way to work it happened and I had to stop for gas, and it drove fine the rest of the way to work... so...yeah...

00t444e

Overdrive and TC lockup are two different things, does the converter lock when it is in the 3rd gear position? I would start by checking the fluid level and adjusting the TV cable.

Vedalkin

I'm sorry for any misunderstanding. It was explained to me that the AW4 is a 4 speed auto with TC lockup, and that the TC lockup was kinda like overdrive. If that is wrong then I stand corrected. The cable has been adjusted and the fluid is great.. I have been running ATF 4 since I purchased her with 37k. I just hit 317k on this original trans, so I swear by the ATF 4.

jordan96xj

Your transmission has 4 gear ratios. The 4th being over-drive. 3rd is direct drive (as in a 1:1 gear ration between the motor and drive-line. That is why 4th in this case is called over-drive. The torque converter lock-up clutch is a separate item and is responsible for locking the torque converter once the 2 halves of the converter are spinning at similar speeds - which helps with efficiency so that energy is not robbed from the motor in the form of heat build up in the torque converter (which until the lock-up occurs is just a fluid based connection). You can watch youtube videos on how torque converters work for more information.

To test the lock-up functionality on its own:
1. With the vehicle in drive (gear selector D).
2. Drive 55 mph straight and level (cruising).
3. Note the engine RPM at this speed.
4. Tap the brake lightly/quickly - not enough to slow the vehicle, but just enough to make the brake lights blink
5. Engine RPM should jump up about 300 RPM (this is the lock-up disengaging because of receiving a signal from the brake switch)
6. After just a few seconds the RPM will drop down the original RPM noted in #3 (this is the lock-up clutch locking back up again).

If you do not observe this change in RPMs as noted in the test above, it can point to a failure of torque converter lock-up. Which can be caused by a failing solenoid (one solenoid in the transmission is dedicated to this function). Or it can also be caused by the computer receiving erroneous input from things like the brake switch, or throttle position sensor, such that the computer believes that it should not lock-up the converter.

(Incidentally, your mechanical fan clutch in the XJ operates like a small simple torque converter as well, where heat from the radiator causes it to lock-up more and more as it gets hotter by opening/closing a small port through which the fluid moves between the two halves of the fan clutch. The more it locks up - the faster the fan spins in relation to the belt/pulley speed.)

Vedalkin

Uhmm, thanks...

wauto

Check and clean all body and engine block grounds first. They cause all kinds of gremlins.