1996 2 Door Cherokee, 4.0L ~218k miles
Hey all; anyone have any comment on how long the transmissions last on the 96 models? I bought mine some years back at about 170k miles; so far as I know it's still running with the factory transmission, not sure of the specific model number. According to my local transmission expert, they last until 250k miles and than die; just curious if any other owners have had such an experience.
I happen to be posting now because I had my first issue with it yesterday when I started up and it wouldn't downshift automatically. Anytime I pulled away from a stop in Drive I had almost no power/acceleration, felt like it was pulling away in 3rd. Shifting it back manually worked though, and I made the rest of the trip that way, starting off in 1/2 and shifting up to 3 and D as I got up to speed. This morning I went out planning to leave it at my garage for a look, and everything was working fine again; drive away in D and it shifts up and down exactly as I'm used to. So it's not an immediate problem, but again, curious if anyone's had a similar experience, and wondering if/when the problem reappears it might make more sense to go right for the overhaul rather than trying to fix it piecemeal.
Any thoughts welcome, thanks.

 

Well I'm at 260+ thousand miles and mines fine. My buddy who bought my previous xj just replaced his but it has 400+ thousand miles. I've never completly change the fluid I just drop the pan and clean the screen and add more fluid has worked for me for many years. That said your problem could also be the tps or tcu just a thought though.

 

If the fluid is changed regularly the trans may outlast the engine.

Your problem sounds exactly how mine started. I had to replace the S1 solenoid to resolve it. It could be as simple as the throttle position sensor or kickdown cable, but I doubt it. Adjust your kickdown cable and try it. If that doesn't help, check the voltage in/out of your TPS, or replace the TPS. You should test the resistance of the solenoids cold and hot.

I didn't have any CEL showing, and no codes present.

PM me for the AW4 diagnosis manual.

 

Well the transmissions actually outlasted the engine already :P; had the original replaced last year with a much younger 97 engine I got a really good deal on.

I did check the fluid level and it looks good; that said I'm not sure when the last time the system was flushed/changed.

No sign of the CEL light, but I'll have a look at the TPS. A couple other people I mentioned it to thought the solenoid was the likely culprit. excess, did yours act up intermittently at first also, or did it just stop shifting until you replaced the S1?
Thanks.

 

Solenoid or a throttle position sensor are suspects.
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted acordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the deined acceptable range causing the ECU to incorrectly fuel the engine. This is noticable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

 

Mine was intermittent at first. It would occasionally not downshift when at a stop sign or light. I thought it was temperature dependent, but eventually ruled that out. Changing the fluid didn't help, and the problem got worse over time until it would never go into 1st when put into D or 3. It worked OK, sort of, when shifted manually. I notice later that it didn't necessarily want to stay in OD or would slip out of lockup for no reason. It wouldn't shift down to 2nd when the throttle was fully depressed, either. Manual shifting seemed to point to an electrical issue. 1-2 always seemed to get 1st, and shifting to 3 got a higher gear, but it was 3rd and not 2nd. If in 1-2 and turning 4500rpm+ it will shift to 2nd by pressure if the trans is OK internally, and mine did.

I tested the TPS, and wasn't exactly sure if my voltage output readings were in spec or not, so replaced it. It made no change in shifting or voltage output. The kickdown cable had been adjusted several times with no change. I swapped out the TCU and VSS with no change.

After searching and reading as much as I could stand, I did find the AW4 diagnosis manual online. My S1 solenoid was definitely out of tolerance. Since its been replaced, my trans has worked very well. The observed issue with intermittent lockup and shifting from OD to 3 has gone away.

Over the 7/4 weekend we made a 860 mile roundtrip with combination of highway and rural backroads, and it performed perfectly. My gas mileage has improved considerably now as well.

 

These transmissions are probably the most bulletproof ones I've seen anywhere. We have combined mileage on both of our XJs of over 412,000 miles on the original transmissions without a penny in repairs done ever. Glad you got yours fixed.

Still, where did you find the AW4 diagnosis manual online? It would be good to have just in case.

 

I dunno, but I have it on my PC and can send it to you as an email attachment. PM me your email address.

 

The intermittent nature of my issues seems to match what Excess is saying pretty closely; I drove for an hour and a half yesterday with no trouble, then today, near the end of a 45 minute drive, the problem returned. Again, shifting back to 1/2 whenever I stopped seemed to keep things moving normally.

The info in the TPS is very useful and I'll see what I get from the multi-meter (though mines digital). If the TPS was bad though, I'd think I'd be seeing other issues like what tjwalker mentioned, and so far (at least between what the tach is reporting and the general feel and sound of the engine) the relationship between RPM's and where my foot is on the gas seems as tight as it ever was. Definitely leads me to suspect the solenoid.

 

Just in case anyone wanders by with the same symptoms I was having, looks like the solenoids are the culprit. I got them replaced (they come as a pack, do one you may as well do them all) a couple hundred miles ago and haven't had a failure to downshift since. Thanks to everyone who posted.

 

I know I blew the O-rings out of the pump on mine at about 190K so when I had the transmission down I had the insides taken a look at and they were in tip top shape for the age. I also had all the external seals replaced while I was at it since I could see some spots where the fluid was seeping out. Other than that I've had no issues with mine.