Mike – Page 38 – The Jeep Guru

February 4, 2012February 4, 2012

Differential Skid plate

Differential Skid Plate with Pinion Protection for Jeep 8.25

I like my 8.25 but there is one thing about the design that really gives me trouble. The big flange at the cover mounting point. I am sure it was added for strength, but I am really good at hanging it on rocks when crawling. And if I get one in there just right I can’t go forward or backwards to get off it.

Also, after Jennifer broke her pinion due to a miss-fortunately placed rock, I decided to try to add some protection there as well.

I used some 3/16 scrap and cut a trapezoid to cover from the flange to the center of the U joint. I used 4″ muffler clamps to secure the plate to the axle. I then welded wings to each side to connect the plate to the clamps.

At the front, I shaped a piece to make a stand-off from the pinion. I then used some all thread to make studs and made a plate across the two bosses on the diff housing to clamp the front part to the housing.

The finished piece looks something like the USS Enterprise.

I added a stiffener to the cantilevered part to add some strength. It may also help push rocks to the side instead of letting them slide straight under.

The whole thing mounts easily with six 9/16 nuts so it is easy to get out of the way. I had planned a flange at the rear but I am going to try it on some actual rocks before I add that part. I may not need it.

January 26, 2012January 26, 2012

Choosing the Correct Axle U joint for a Jeep Cherokee

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.

January 25, 2012January 26, 2012

Repairing an Axle U Joint on a Jeep Cherokee

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.

January 23, 2012

The Legend of Eagle Down

While traveling across Monteagle Mountain I noticed that the signs of an old Indian story that my Grandfather once told me are still there alongside the roadway. Some of them even looked new.

My Grandfather told me of a beautiful Indian maiden of the Cherokee tribe who was betrothed to the son of the Great Chief who had built the stone forts on the west side of Monteagle Mountain. Eagle Down was known for her sharp features and soft copper colored skin. She was delicate and empathetic as young maidens were trained to be. However she also possessed the passion and tenacity of her namesake.

The stone carver’s son was a handsome lad who was also very clever in the ways of carving and stacking stones. His father proudly referred to him as a “chip of the old block.” He greatly respected his father and the traditions of the Indian tribe.

Eagle Down loved him greatly even though she was more progressive in her views. Her passion burned inside her and she did not understand why they needed to wait until the Summer Solstice to marry. She knew what she wanted and she wanted it right then.

On day in late spring her impatience and passion burned inside her. She began teasing her betrothed and questioning his virility. She went so far as to assert that his brother Pebbles might make a more suitable mate for her.

She walked off holding Pebbles arm but dashed off to her family’s hut when she was out of sight. The next morning she awoke and went looking for her betrothed. She was told he had gone hunting in the mountains. He planned to bring back a huge buck to prove his virility.

Eagle Down went out to the edge of the camp and waited. She waited all day for her betrothed. She began to wish she had not been so cruel in teasing him. She had only hoped to get his attention not send him on a fool’s mission.

At supper time her parents came to get her. She refused to move. She waited all night for him to return. When he did not return the next day, she decided to go looking for him. She had heard him talk about the large deer that grazed about the cliffs of Mount Eagle. She packed a bag and set out in search of him fearing that he may have been injured or was too embarrassed to come home with out a prize deer.

She searched and searched for him but could not find him. Eventually, she returned home to see if she had somehow missed him on the trail. She was told that if he did not return that she would marry Pebbles on the solstice instead. She slipped out in the night to continue her search.

After many days of searching, she was tired and hungry. She came across a settlement of white people in the forest. They took her in and taught her English. They agreed to help her in her search. They helped her make signs and placed them along the main paths, trails and eventually roadways.

These signs are still visible in the mountains today. As you travel, you will often see the bright yellow signs that Eagle Down put up in her search for her beloved son of Chief Rock Carver: “Watch for Falling Rock.”

January 17, 2012January 17, 2012

Jeep Cherokee Tune Up

Jennifer’s XJ has been running a bit rough lately. We decided to try a tune up to see if the engine performance would improve. The spark plugs and wires on her engine were on the engine when we swapped it in a few years ago so we did not know how old they were.

We obtained a Tune Up kit from Crown Automotive. The kit contained wires, Champion Spark Plugs, a Distributor cap, a rotor, a fuel filter, an oil filter and an air filter. We elected to hold the filter changes for later and just do the ignition parts swap.

We began by marking the new distributor cap with the plug number for each terminal. Next we sat at the kitchen table and set the gap on all the new plugs to 0.035 using my Jacobs gapping tool. I sometimes run a larger gap but for this engine I decided to just go with the factory specs.

Next I removed the plug wires. This task proved very difficult as they seemed seized to the tops of the plugs. Even with my plug wire removal tool, several wires broke before separating from the top of the old plugs. With the wires removed, I used a 5/8 spark plug socket to remove the old plugs. I carefully cleaned the area around each hole and inserted new plugs. I ran them down until the sealing washer hit and then turned then an extra quarter turn.

The old spark plugs were the proper tan color indicating that the mixture was correct. However, they did show a great deal of wear on the tips.

Next I removed the old distributor cap by loosening the two Phillips head screws that hold it to the distributor. I left the old wires in place. I then installed the new cap and tightened the bolts.

The old distributor cap showed signs of severe pitting on the internal terminals. There was also some evidence of cross tracking inside the cap.

Jennifer carefully selected the matching wire for each plug from the kit and installed it on the appropriate terminal on the cap and then routed it to the plug as marked on the cap. She set the wires in the holders and then replaced the coil wire.

When she started up the engine, we immediately noticed that it ran much smoother. Hopefully there will be a corresponding increase in fuel economy as well.

Note that we did not install the rotor from the kit. When I ordered the kit, I forgot that she was running a 96 model distributor in her 1992 model Jeep. The cap is the same but the rotor is not. We will source a rotor separately and install it later.