[Fourspeedman]

This happened Loud banging from my rear So I ordered a new set of spider gears. The Jeep parts are discontinued and anyone who has them thinks they are made out of gold and uh, can't be sold. So I had a choice of Richmond Gear ($100) and USA Gear ($200). The Jeep set comes with an assortment of washer/shims to measure and use the right one for proper side gear clearance. The Richmond set showed only two shims. I called and asked why everyone else showed a set of shims but the tech guy was not any help. I see they do sell the set of washers separately for $30. So I ordered the USA set which should have the washers and is forged (USA) vs cast (Richmond). Once I removed the spider gears I see the washers are worn so bad that one broke. The pinion gear shims are very worn too. The actual gears look OK but my calibrated eyeballs are out of whack these days. Why take chances. I think the shims wore so badly that the gears wore down as well. The ring and pinion set look good and the backlash is OK. Hopefully no other damage occurred. I am adding a screw-in fill port as well to replace the crappy plastic plug that always leaks. I seal it so it won't leak but then I don't check the oil enough. I will weld on an O2 sensor bung and use an 18mm x 1.5 plug to seal the hole. Now I can check the oil level properly.

 

[Fourspeedman]

While waiting for the parts I went and welded the bung to the cover. All it is, is an 18mm x 1.5 big nut but it was all I needed. I used my oxyacetylene torch because I prefer it when doing exhaust and other stuff I don't want to leak. When I see bubbles that will later become a pinhole leak I can push the molten metal around with the gas pressure to fill in with. I used a big copper brake fitting washer on the plug as they rarely leak. Next some paint and it will be finished and ready for use.

 

[Rob K]

That should last longer than the rubber plug as long as you can keep the rust away. If you have the time it would be nice to see how you go about doing the gearing. Wondering if rebuilding a diff is tricky to get right or pretty simple.

 

[Fourspeedman]

Rob how easy it will go will depend on if the gears I ordered come with an assortment of shims. The FSM want to see between .003" and .005" clearance on the side gears. The pinion gears are not adjustable they are spinning on shims that are one-size-fits-all. With them in place you measure the side gears and adjust accordingly. This is my first Jeep differential but I am well versed in GM rears. Same arrangement, same headaches, same lack of maintenance. I probably would have gone along clueless had I not overexerted it towing the boat.

 

[Fourspeedman]

The gears finally came. I was pleasantly surprised to see that they were YUKON gears in a YUKON box. I thought USA Gear as a cheaper brand of YUKON but I got the good stuff, and with a set of adjustment shims. First I took my dial indicator and checked the ring and pinion backlash. I got .009" which at 180k is pretty damn good considering .005"-.008" is the range. Knowing the R&P was not the issue I replaced the old spider gears for a baseline measurement. With the original .038" washers I had side gear clearance of .024". That is pretty bad as .005" is acceptable. I removed those and measured the new shims that came in the kit. They measured at .048", .039", and .030".

First I placed the side gears in with the middle set of .039". With just the side gears in place the pinion shaft was very tight to the axles. There was no clearance at all and the shaft could hang there all by itself.

Then I tried the thinner set of .030" washers and I had a very sloppy .030" side clearance. That told me to go back and try the .039" washers again. This time I added the spider gears. It is frustrating to try and get the spiders and their cup washers in place properly to accept the pinion shaft when the carrier is in the axle housing. Most videos do it on a bench and that is fine. I am working with the carrier in the car so I accept the aggravation. You rotate an axle to get the spiders to revolve around the carrier. You need a lot of patience and just advance/retard the gears a tooth at a time so the other does not fall out the back. Once they are in place you slip the pinion shaft in so they won't wander. Now you can measure again as the planetary gears are spreading the side gears. I found .003" clearance on both sides and that is spot on.

Just to satisfy my own curiosity I mounted the dial indicator to the carrier to measure the spider gear backlash. I got .006" backlash. That matches up to the .003" on both side gears. I find that very interesting because it would indicate all of my spider gear play was in the gears themselves. The original washers were .038" and I had .024" side gear clearance. With the new .039" washers I have .003". Assuming the OEM washers were .039" and they only wore .001" in 180k miles then all the play was in the worn spider gears. Now when I check the play at the driveshaft I have very little compared to when the gears were banging. I inserted the pinion shaft retainer bolt which has a patch of Loktite on it. I torqued it to 12 ft lbs. Next is to get a gasket and seal up the rear then fill with oil.

 

[Fourspeedman]

Here is the backlash of the spider gears. The dial indicator is mounted by magnet to the carrier. .006" of play. The old gears I could see them lift up and get cocked between the side gears. That was how badly worn they were.

I used a paper gasket on the cover. I schmear some Ultra Black on both sides. That never leaks. I will give it over-night to cure before adding fresh gear oil. Notice the welded O2 sensor bung with a threaded plug for checking the oil level.

 

[Fourspeedman]

Just a heads-up. The Chrysler 8.25" rear was used from 1961 to 1989. There are aftermarket differential covers available that already have the screw-in fill plug. Jeep picked it from 1991 to 2001 for the Cherokee. Those have the stupid plastic plug. If you won't or can't weld a plug on, the '61- '89 aftermarket cover will do just fine.

 

[Rob K]

I've pulled axles and have done wheel bearings but never have done gearing. I always thought this was a difficult process but it all seems pretty simple. Simple process to check clearances with a feeler gauge. I don't understand what backlash is. It appears you are checking for any wobble in the spider gear, checking to see how true it spins. I assume there are specs for all the gears. I need to learn how to do this someday. Thanks for posting.

 

[Fourspeedman]

Backlash is just the play between the gears. When I did my first rear all I had was feeler gauges and that worked well at the time. The wobble is called runout and yes, there is a limit to what is allowed, not much. Doing the entire rear with the ring and pinion is a complicated process and you need some special tools. I have found buying the used tools cheaply on Fleabay is a great way to compile a tool set for special jobs. For example I was afraid my ring gear backlash may need to be adjusted. It did not but a knockoff of the Miller Tool C-4164 side bearing pre-load adjuster tool is around $30. That and a torque wrench will set up your carrier bearing pre-load. I am mostly a GM guy and years ago I found a GM stealership Pinion Depth Setting Tool Kit at the swap meet at Englishtown for $100. I have done lots of rears with that kit and it paid for itself many times over. If you have the FSM it is all explained but can be vague at times. Any questions just fire away.

 

[Fourspeedman]

Update: As soon as I road tested the XJ I heard the click-click-click sound again. My first impulse was to set it on fire but then I remembered I thought it was a U-joint to begin with. I dropped the rear driveshaft and it seemed OK. I sent it to my driveshaft guy anyway for new SPICER U-joints with grease zerks. He said it didn't look bad either but what the hell. Well, I got it back and put it back up in the XJ, greased the zerks, greased the slip joint, checked everything, and tried it. NO NOISE! So I suffered two whammies at the same time. I will drive it around slowly to let everything break in as per the YUKON instructions. I had watched two YouTube videos of guys that attached GO PRO cameras to the underside of the Jeep and listened to the driveshafts. The first one went scratch-scratch-scratch like mine USED to. The second one went click-click-click just like mine did. That did it. I KNEW that sound was U-joints and I was right.

 

[Boojo35]

Nice work. Nice write up.

 

[Fourspeedman]

You are welcome. When I got my first Jeep this site was the only place I could find good information. I lurked for years. Now I am maintaining three Jeeps and whatever I can contribute I will.

 

[Rob K]

Glad you got it fixed, you should be good for a while.

 

[Fourspeedman]

Rob I enjoy using my SAE tools again because there is minor metric stuff on Jeeps. I just wish I did not have to use them so much!!!!!

 

[N8N]

FYI, if Lube Locker makes a gasket for your diff I can't recommend them enough. No futzing about with RTV and when you have to pull the cover, no scraping or surface prep, just wipe off and reassemble. have used them on my last two Heeps, and they even make one for an AW4 now although I have yet to drop the pan, that's the one maintenance job I've been putting off because of the damn dipstick tube.

 

[Fourspeedman]

Aaaaand, the sound is back. I guess I was wrong. It feels like all I did was make things a bit better, but I still haven't found the culprit. Although multiple problems at once is my style. EDIT: I am seeing that the Chrysler 8.25" rear is the red-headed stepchild of the Jeep world. There are very few parts available for this rear. The DANA is the king and everything is available. I was on the YUKON site and nothing was for the 8.25". I am thinking my bearings are shot and allowing the ring and pinion to clash. Maybe I can get a whole rear somewhere.

 

[RLE]

I recently rebuilt my 8.25 with a Timken differential and pinion bearing kit. Shortly afterward, I began hearing click click click from the rear. Turns out an outer side bearing was bad and disintegrating. Fixed that and heard the same sound a couple of weeks later. The bearing on the other side was bad. Perhaps we didn't get all the debris out of the axle tube from the first bearing and some chips found their way to mess up the bearing on the other side, I don't know. Anyway, if you have a click click sound, it could be the outer bearings.

 

[Fourspeedman]

Thanks for the input. When I had the axles out the bearings looked fine, no flat spots, chips, binelleing, nothing. The click is bad enough but then it escalates to a loud snap sometimes. In 4wd under a lot of load it goes away, then on decelleration, it snaps. I have three choices. Get a used rear, rebuild this rear, set it on fire.

 

[Boojo35]

If it happens on decel I have two thoughts. The coast side of your gears has a chip or something. But I would really suspect your pinion bearings.

 

[Fourspeedman]

On decel in 4wd. In 2wd it happens under moderate forward load. Click-click-click with an occasional snap. Used to be a BANG but that stopped after I did the spiders. I am looking at replacement rears. Are all 8.25 rears in an auto trans XJ 3:55? And manual trans are 3:07?