Homey

Hello forum.

I have a 1998 Cherokee XJ with 4.0 liter and Auto Transmission.

I use this for work. While out working the Jeep idles all day long and is a constant forward, reverse, drive 200 or 300 feet stop again. In 8 hours I typically cover a total of 15 miles.
Thursday I had been doing this for about 5 hours when I had to move to another area a few miles away. The trany had been shifting slow most of the day and as I got on the main road it started to slip and within a mile it was slipping bad. Not going anywhere. I pulled off the side of the road. shifted in reverse would not move. Back into drive, 1/2 and nothing. It would not move at all. Shut her off and sat there for about 10 minutes hoping that I just got it too hot and fluid needed to cool. Fired it up and drove fine.. Drove back to my hotel 15 miles away and parked it. This was Thursday. Yesterday I drove 1/2 mile away to DD for coffee. Figuring as long as my fluid stays cool and I get it flushed soon I will be fine. That was wrong..
I was in there for less than 5 minutes, came out and it would not go anywhere. The tranny was not hot. The temp for the engine was only at about 150. Turned the truck off only to find that it would not turn over.. So with the key turned I started wiggling the shifter and bam it fired up... Tranny seemed to work fine all the way back to the hotel. Did not drive anywhere else..
Today I went out to go DD for coffee again and stop by the 2 local auto parts stores for a diagnostic. The truck would not start. Put it in Neutral and it started, but it would not go anywhere. Turned it off, started it up again (wiggling the shifter) and it works but not 100%.. It now takes a long time to shift between gears. But at least I can drive a little bit..
Went to both stores only to find out that neither one would run a diagnostic on it for me. And if I knew what part I needed for certain they could not get it for me..
So now it will not start unless I push the shifter as far forward as I can or put it in Neutral. It shifts gears and takes off fine but shifts slow, meaning it is a long, slow shift as you can feel the next gear engage slowly. Some times it will not move at all but If I turn the truck off then start it again it works..

So what is it? T.C.U going bad? N.S.S gone bad? One of my speed sensors? One of the solenoids bad? All of them going? Is my tranny shot?

I need some help here please. As I said I am in a hotel, with a vehicle I am scared to drive very far. 16 hours from home and do not have a ton of cash to stay here long..

Thanks

Jesse Hallum

The no-start problem sounds like a classic NSS issue. The "slipping" transmission can be any number of things. Check fluid level and condition. If it looks/smells burnt, you will likely need to consult with a transmission expert for options. If it has not been serviced and filters changed in a while, it may just need some attention. I've seen neglected transmission filters so clogged that it causes problems that you describe.

Homey

Thanks for taking the time to answer.. My fluid is fine.. Slightly over full but not burnt or dark. That was the first thing I checked..

I do find it odd however that this problem with the tranny not moving and the NSS all in the same day. Unless it is the NSS or the TCU are causing all the problems..

Jesse Hallum

Glad to hear the fluid looks okay. This is very likely NOT a transmission problem.

I would start by isolating the NSS as one problem. If it will start by shifting to neutral after a no-start in park, or by jiggling the shift lever while holding the key in the start position, replacing or cleaning the NSS should remedy the no-crank problem.

On the transmission shift issue, I know that the NSS controls OD/gear 4 and 1/2 gear engagement. One other input sensor that most often causes transmission shift problems is the TPS. I had transmission shift problems on an old Ford in the 90's that traced back to a bad TPS, and I was convinced it was a transmission issue before the MIL lit up. If yours is original or was replaced with an aftermarket cheapie at some point, it's worth replacing with an OEM part as a maintenance item anyway.

Homey

Thanks for the response again.

TPS? As in throttle position sensor?
Would this sensor keep the transmission moving in forward or reverse. Like It was not in gear at all?
When it won't move it acts like it is neutral when I am in drive or reverse.

As far as I know it has never been replaced. I bought this jeep in 05 and it has never been replaced since I have owned it.

Radi

Jiggling the shifter to start is a dirty or bad NSS. You can remove and clean them.

The shifting issue- if the problem clears temporarily when you turn the ignition off then back on, it's almost certainly an electrical issue, not an internal transmission issue.
TPS has a lot of input into shift decisions, as mentioned previously.

Another thing to try is to disconnect the TCU (or pull the fuse) and try shifting manually. 1-2, 3. That shifts the transmission through the valve body instead of the solenoids. If that works normally (not shifting to second until you hit high RPM is normal in 1-2), check the resistance of the solenoids, the wiring harness, voltage and ground to the TCU. Might be the solenoids are sticking, or have insufficient power applied or a bad ground.
FWIW, if the transmission operates normally when shifted manually with the TCU disconnected, it's perfectly fine to drive home that way. You won't have overdrive or TCC lockup though.

Homey

What is TCC lock up? And exactly how far and long is it safe to drive like this?
I pulled the wire harness out of the TCU and Reverse work good. Then I can manually shift 1/2 to 3 that all works fine.. Just can't use drive like normal.
You said home but over 1000 miles? I can deal with no OD not a big deal unless I want to drive on the Interstate.. But what is the TCC lockup? And do I lose anything else having the TCU unplugged?

Jesse Hallum

I agree, and Radi makes a very good point: with the TCU out of the loop *and* the transmission shifts okay, the problem is likely not the transmission, but the computer.

This may not make any difference, but perhaps clearing/resetting the computer will clear the problem up? The steps are outlined below, it costs nothing and it just takes a minute to complete. Let us know if it helps.

Running 1000 miles w/o gear 4 or overdrive will not hurt your Jeep. Do what you have to do to make it home, and don't worry: your horse will get you there.

---------

To reset the computer, remove the positive battery cable; touch it to the negative battery cable for 30 seconds. Reattach the positive cable back to the battery. Now turn the ignition to ON but do not start; turn headlights on, then off. Turn key to the OFF position. Your computer has been reset, and will now begin to relearn how to efficiently manage powertrain operations during the next 20 minutes of driving.

----------

Radi

TCC = Torque converter clutch. It locks the torque converter above 40-some MPH under steady load to increase MPG and keep the trans a bit cooler.
You can drive as far as you want with the TCU unplugged, you'll just have a bit worse gas mileage. Interstate driving is fine without Overdrive, the rpm's will just be a bit higher. That motor was designed long before Overdrive became common, the AMC version spent plenty of time churning plain old 3-speeds.

RedHorsey

sorry for hijacking, but does anyone have/ know of correct voltages for the TCM wiring harness? My 95 XJ is stuck in 4th no lockup D, stays in 1st in 1-2 selection, and 3rd selection gives me 3rd no lock up. Its like the TCM is unplugged but it is. I have checked said TCM in another cherokee and its fine. any help would be appreciated.

BatmanXJ

Simple check free total of 5 mins with test drive. Would bebthe throttle kickdown adjustment. No start sounds like NSS.