Jeep Cherokee Forum

Jeep Grand Cherokee 1993-1998: Transmission Diagnostic Guide

Automatic trans problems can be really scary and expensive too. But they aren't always, as we will see.

By Mark Garrett - October 13, 2015

This article applies to the Jeep Grand Cherokee ZJ (1993-1998).

Nobody wants to have trans problems, as they are usually stupid expensive, but that may not be the case with your Jeep. In fact, it would be unusual if it is something big—unless that boulder you crawled over broke the transfer case! We will look at the top causes, so you can check them off of possible issues and by the end you will probably be back on the road, or trail.

Materials Needed

  • Transmission fluid
  • Rags
  • Screwdriver
  • Assorted wrenches

At some point, you may need to pull the trouble codes from the PCM (Powertrain Control Module), but there are things to try first.

Step 1 – Check for leaks

The trans cooler lines at the radiator are a known leak issue with your Jeep. Part of the factory fittings are plastic and breaks over time. You are better off fixing them yourself rather than buying factory replacements for $175. Just run the appropriate hose from the metal lines to the radiator and use a hose clamp tighten well.

  • Figure 1. Cherokee factory trans cooler fitting.
  • Figure 2. Cherokee factory trans cooler line fitting cut off.
  • Figure 3. Cherokee factory cooler fitting replaced with hose clamp.

Pro Tip

While this may not look like the factory setup, it will work quite well.

Step 2 – Check your trans fluid

Low trans fluid can cause all kinds of things.

  • Make sure your Jeep is warmed up and setting level.
  • While it is running, pull out the trans dipstick and make sure the level is between the marks.
  • If it is not, carefully add fluid.
Figure 4. Trans dipstick.

Pro Tip

While you are checking the level, see if the fluid is pinkish and smells fresh. If it is brown and smells bad, you have another opportunity.

Step 3 – Replace fluid and filter

Dirty fluid is like poison. Dirty fluid needs to be changed. The fluid is what makes your transmission work, so it needs to be good. Take a look at the related article How to Change Transmission Fluid to find out how.

Figure 5. Dirty trans fluid on dipstick.

Pro Tip

Don't be concerned if you need to change your trans fluid, it is pretty easy.

If all is fine so far, try Step 4.

Step 4 – Adjust TV cable

The Throttle Valve (TV) cable tells the trans when to shift. Over time, it can get out of adjustment. If it is, up-shifts may be delayed or not happen. This is another easy fix for your Jeep. Check out the related article How to Adjust Kickdown TV Cable.

Figure 6. Jeep 4.0 TV cable.

If your Jeep is stuck in gear or will not go into Park, try Step 5.

Step 5 – Adjust shift linkage

If the shift linkage is not adjusted properly, the transmission will not know what to do when shifted.

There have been issues with Cherokees not being able to be taken out of Park, put into gear, or being difficult to do. There have been recalls, but if all it needs is adjusting, you can do that.

Figure 7. Shift cable adjuster.
  1. Shift trans into Park.
  2. Raise vehicle.
  3. Release cable adjuster clip at transmission end of cable to unlock it.
  4. Remove cable from cable mounting bracket on transmission.
  5. Slide cable end off transmission shift lever.
  6. Verify transmission shift lever is in Park by moving lever, so cable would be all the way in if hooked up. Last notch is Park position.
  7. Be sure the shift lever is fully engaged in Park. Drive shaft will not rotate when park lock is engaged.
  8. Slide cable end onto transmission shift lever.
  9. Put shift cable back into mounting bracket on transmission.
  10. Lock shift cable by pressing cable adjuster clip in until it snaps into place.
  11. Lower vehicle and check shifter detents in car.
Pro Tip

If your Jeep still will not go all the way into Park, go to the dealer and see if it is covered under the recall to get a new shifter plate.

If your Jeep will not start, see below.

Step 6 – Check the neutral safety switch

If this switch does not tell the PCM that it is in neutral, there is mass confusion.

The neutral safety switch (NSS) tells the PCM that the transmission is in neutral. If it can not sense this, your Jeep will not start. The NSS switch is a common issue with Jeeps. Fortunately, instead of spending $400 at the dealer, you can clean it yourself. The NSS is on the transmission and can be taken apart to be cleaned.

  • Figure 8. Cherokee neutral safety switch.
  • Figure 9. Switch disassembled.

Step 7 is another solution to no shifts.

Step 7 – Replace speed sensors

The speed sensors tell the PCM what to do.

Trouble code P0720 points to a bad speed sensor. Depending on which trans you have, there are either one or two. They are relatively cheap at $20 to $30 each and take 10 minutes to change. There are two styles, the bolt-on or screw-in.

Figure 10. Speed sensors, bolt-on

Pro Tip

You can check the sensors with an Ohm meter. If they show open, the sensor is bad.

Things get more tricky if those don't help.

You would want to get the PCM codes read for sure if you still have issues. Worst case, you have bands that are needing adjusted, a shift solenoid is faulty, a P1756 code indicates a faulty governor solenoid, or you may actually have a bad trans, which is rather rare fortunately. Remember if the problem is tricky, there is no shame in asking for a pro to help.

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