Category: Car repair

Choosing the correct Axle U joint for a Jeep Cherokee

There seems to be a lot of confusion over the correct U joints for the Jeep Cherokee at various parts stores. Autozone lists at least three different U joints for the axle shafts. Only two of the ones they sell actually fit a Jeep.

There are two different sizes of U joints for the front axle shafts. The 174 and the 297. The smaller joint is used mostly in axles with out ABS. The smaller joint has a 1.062 inch cap and internal c clips. The larger joint has a 1.189 inch cap. These were used in the early axles with ABS and later axles regardless of ABS.

The best way to make sure you get the right joint is to measure the cap. Buying by application is like a coin toss. Since the axle shafts interchange, the axle may have been swapped. Also, the AMC vintage Jeeps are known for having odd mixes of parts.

Autozone lists a 1.125 diameter cap joint (2-1175) for many of the ABS axles. I have never found an axle shaft that these will fit. In fact, the space between the clips is wrong and you can damage the axle shaft if you try to get it in. They also do not like to give refunds after you have attempted to install the U joint.

I generally prefer to use Spicer brand U joints like Jeep came with from the factory. These seem to hold up best. However, I no longer have a local supplier that stocks the Spicer Joints. So, if I am in a rush, I use Advance Auto or Auto Zone. The Spicer U joints are available through my Crown Distributorship.

Repairing an Axle Joint on a Jeep Cherokee

Last week I decided to repair the U joint in the right front axle of my Jeep Cherokee. I had noticed some rust stains around the grease seal a while back indicating that it had lost its lubrication. I recently noticed that the joint had some slop in it. Before leaving on a trip, I decided to replace the joint so it would not fail on me on the road.

I picked up a new U joint from the parts store on the way home. I picked up my Cherokee and removed the wheel. I then removed the brake caliper and rotor. Next I removed the 36 mm nut on the end of the axle. I then removed the three 12 point 13mm bolts from the hub.

AS usual the hub was stuck in the knuckle. I used my three sacrificial bolts to remove it. I threaded in the bolts a few turns into the hub and used a hammer to strike the bolts heads. These bolts have been used several times for this task and the heads are quite beat up now. Once the hub separated from the knuckle, I removed the bolts and pulled the hub and brake shield off. I then slipped the axle shaft out of the housing.

I carried the shaft to my vise and used my U joint press to remove the worn joint. The C clips were rusted in place. I had to soak the assembly with PB Blaster and use several strikes of the hammer on my specially ground chisel to get them to pop loose.

When using the press to remove a U joint, I have found the best success by tightening the press and then striking the press bolt with a hammer. The hammer does most of the work. Trying to tighten the bolt in the press enough to move a stubborn U joint has very poor results. I have much better success with the tighten-and-strike method.

One the U joint was out and I confirmed that one of the caps was totally destroyed by rust and wear; I opened the box for the new U joint. That is when I realized I had purchased the wrong U joint. I had forgotten that some years ago I had updated the front axle in this Jeep to a 99 axle which uses larger U joints than the 1991 originally came with.

Since it was well after closing time for the parts store and I had a trip to make the next day, I set about finding a temporary solution. I considered pulling a shaft from my off road XJ. I considered swapping in a couple of two wheel drive stub shafts.

I looked around and found a CV shaft in a pars Jeep behind the barn. The Jeep is a 1985 XJ but has ZJ axle shafts in it. Both of these Jeeps use a Dana 30 with CV axles.

I hammered the hub out and carried it to the shop to separate the bearing from the axle shaft. I inspected the boot. It felt stiff but there were no tears or holes. I slipped it into place and put my hub back on. Setting the bearing preload was a bit of a challenge with the CV axle. I normally just slide a bar through the axle yoke and use the torque wrench on the nut. Since there is no yoke on the CV shaft, I had to use the bar through the wheel studs. Having to pull two bars to 150 foot pounds was a bit of a challenge but I eventually felt the click in the torque wrench.

I then put the rest of the wheel assembly back and took it for a test drive. It felt nice and smooth.

After my trip, I picked up the proper U joint for this axle shaft. I used my anvil and a hammer to drive in the new joint. It went in easily.

I then pulled the hub off to remove the CV shaft. I noticed that there was grease on the brake caliper and on the inside of the axle housing. I rotated the shaft around and found a gaping hole in the boot. I also found a small twig in the grease. I guess the little piece of wood cut the boot or maybe it just failed due to age. Either way, I am glad I already had a replacement made up.

I slipped the axle shaft back in the housing. When I went to slip the hub back on, it did not slip freely on to the splines. Upon very careful inspection I found where the splines on the ale shaft had been slightly damaged while it was out; possibly during the U joint removal process. I used a three sided file to clean up the burrs until the hub slipped on easily.

I then bolted the hub in place and set the bearing preload to 150 foot pounds. This time I used a bar through the axle yoke being careful not to damage the U joint seals. I then reassembled the brakes and reinstalled the wheel. A test drive showed the new joint to be just as smooth as the CV shaft.

See the next article for how to choose the proper U joint for the axle shaft of an XJ.

Replacing the Throttle Position sensor in a Jeep Cherokee

Jennifer’s 1992 Jeep Cherokee has been acting up lately. It has had a severe stumble at times but the stumble has been intermittent and unpredictable. I was guessing an ignition problem so I ordered a Crown Tune up Kit. However before the Kit arrived, her Jeep took a very severe stumbling fit one morning. During this particular event, the check engine light came on. Code 24 came up. That translates to trouble with the throttle position sensor.

I took her Jeep for a test drive and found that just off idle, the engine would nearly die unless you pressed the gas pedal down further. Coming back to idle it would do the same. I had to let off the gas completely to keep it for dieing but then it would idle fine. There seemed to be two trouble spots in the throttle position sensor and as long as you avoided those, the engine would run fine. The trouble was, these two spots were nearly impossible to avoid in city traffic.

I looked up the replacement sensor. Advance Auto had
a BWD Throttle Position Sensor for under $40. I could sell one from Crown for $25 or so. However, I noticed that a 1996 ZJ had the same part number. I remember that there was a ZJ throttle body somewhere in my spare parts pile.

I had her drive her Jeep to my shop. She had some trouble to but was able to get it there. I found the manifold behind the barn and set about pulling the TPS off. It took a T20 torx. The bolts were slightly seized in the aluminum body so I used a pair of vise grips on the torx driver handle to get the extra leverage I needed to twist them out.

I looked at how the throttle tang engaged the sensor. There are two tangs inside the sensor that catch on the blade of the throttle shaft. Due to the preload of the spring in the sensor, you can’t just push it straight on. You ha to twist it a bit, slide it on the shaft and then rotate it to align the mounting holes. I was glad I had the spare throttle body to practice on before I tried it with the one on her Jeep.

I used the same vise grip trick to loosen the T20 bolts holding hers in place. I unclipped the wire and slipped the sensor off the shaft. I rotated the sensor slightly and then pressed it into place on the throttle body. I tightened the two bolts and then reattached the wire.

I started up the Jeep and checked for the stumble. I was very happy that it was gone. There was a high idle condition that lasted a minute or so but one it settled into the proper idle speed, the condition never repeated. I guess the computer was adjusting to the new TPS.

A road test showed that the stumble was completely gone and the Check Engine light did not return. I was very happy that the engine code came up when it did. Otherwise I would have been disappointed that the tune up did not cure the stumble. The tune up kit will still be installed but at a later date.