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Save the U-Joints!

Contributed By: James Jezak

        Recently I was driving my ’78 Cherokee w/ QT to work and was noticing a noise coming from what sounded like the passenger side of the transmission hump. It sounded like when you’re in a commuter airplane when they’re testing the engine before flight. The noise rippled through the body. (Please don’t be the transfer case!) It happened only at certain speeds with power applied. When I parked I revved the engine in neutral and there wasn’t any noise so that told me it had to be the drive train.  That evening, the possibility was narrowed down to the front drive shaft.

Since the shaft was nearly grit free from the tranny fluid dripping off a temporary transmission cooler line onto it, and I personally had only gotten around to greasing the very front u-joint I knew that one of the joints by the CV joint was going out. Although I’ve done dozens of u-joints in my jeeps before (especially the CJ-7) I have never had the “pleasure” of doing the front drive shaft off of a Full Size Jeep. This may/may not apply to FSJ’s with the 20/228/229/208 etc. transfer cases since I haven’t been under one of them.  Here’s my advice to you if you have the original u-joints in yours like I had in mine. TAKE IT TO SOMEONE ELSE. Just kidding. With a little perseverance and a lot of time you can get it done, have a reliable front end, and save some bucks.

The first step is to clean the underside of your vehicle and get it on a flat, clean, surface and set the parking brake then chock it. I had to do all of this on the driveway- it would be a lot easier with some fancy shop equipment. I used a 9/16” box end wrench since a ratchet won’t fit behind any of the bolts.  This step will take around 20-40 minutes. The front u-joint practically falls off by itself after loosening the u-bolts from the front axle yolk. Don’t get too anxious to get it on the bench yet though, the back set is another story because the bolts unbolt towards the QT unit. There is enough room to turn the wrench about 1/8 to 1/4 turn each time. After each bolt is loosened, then you have to rotate the drive shaft just a little to get to the next one. I just rolled the Jeep a few inches forward or back to get it in the right position the re-chocked it.  It’s a relief when the drive shaft finally comes loose and you can remove all 400 lbs. of it to your workbench. The first thing you want to do is clean as much gunk off of it as you can and for that I used a wire brush on the whole thing. Now that you can see it you can start pulling out the u-joints. I removed the end cap “c” clips with a pair of needle-nose pliers and a screwdriver. It was amazing that half of them were broken in half and fell off after wiggling them out of their groove.  If you have a press- consider yourself lucky because now the fun starts.  Place the shaft on a block of wood with the end of the joint just over the edge of the wood   or over a proportionate sized hole in the wood. Start with the QT end of the CV joint and spray some lubricant around the caps to help them out, and removed the zerk (grease fitting) . Goggles are suggested. Mark the CV and drive shaft on the same side so there won’t be any chance of getting it out of balance.  I used a cheap spark plug socket that was about the same diameter as the outside of the end caps on the u-joints – the word here is cheap quality/price because it was mushroomed on both sides by the time I was done- and promptly beat the heck out of one side of the joint until the opposite seal of the joint was flush with the downside of the yolk. (I have a 20-oz. hammer for this and I would not recommend anything lighter.)  Flip the shaft 180 degrees and CAREFULLY start knocking the joint back the other way on the side crosses of the joint until its seal is in the same position. (Don’t hit the inner threaded section of CV that is half way around the cap- it will get damaged!) The CV will move out of the way enough to remove the side caps after a little bit and give you some more room. Flip it over again and drive the first cap totally out then remove the u-joint. Use a screwdriver or a punch to knock out the remaining cap.

NOTE- the CV ball and half end yolk will probably come off after this u-joint. Don’t loose the needle bearings or the spring inside of it! Check the seal around the ball- mine was shot so a new inner CV section was taken from a spare shaft I had to replace it.

The same process goes for the other joint on the CV. The one at the front of the drive shaft is the easiest. After everything is disassembled clean it up thoroughly, paint it if you want, and take five. 

REASSEMBLY:

Take your freshened drive shaft, lube the yolk holes for the end caps and place the inner side of the yolk down on the wood so you can tap the caps in just a little bit. Insert the new u-joints end cap into the front-end outer-side hole of the shaft. (make sure the needle bearings inside don’t get lost or misaligned because they only come with minimal grease on them) I used regular zerk cross fitted joints on the front two and a flush end cap fitted zerk on the rear to ease future maintenance.  Tap one in until the seal starts showing and the other just barely in. Re-check the needle bearings and insert the capless end of the cross into the opposite yolk hole, then put the other end fully into the partially inserted cap. While holding the joint- tap the other cap into contact with the joint, align both ends, and insert “c” clips on the yolk grooves check for binding.  It is basically the same process on all the u-joints except the QT end of the CV – recheck the CV ball needle bearings, put some grease in the ball, insert the spring and half yolk, and then start putting in the u-joint. 

After assembly- grease joints and CV ball thoroughly and test for binding again before putting it back on the Jeep. I would recommend greasing the shaft itself after reinstallation.

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