Popping the diffs

New Jeep is in my garage and I've been checking things out. On the top 10 list of things to check, I'm about to pop the diffs, inspect, and change out the gear oil. I've got a 73 304 V8 3sp... anything I should be on the lookout for (while I'm in there, near there)? Heard that the gear oil could look like a chocolate shake if it was neglected. The PO changed the regular oil every 6 months whether it needed it or not, but not sure on the gear oil. We shall see.

-Troy

 

You can look for obvious carnage. Any pieces of gear teeth or such.

The rear axle on these Jeeps often has a TracLock differential, which requires limited slip additive.


Lockers & Limited Slip Differentials - Jeep-CJ Forums

Oil in good condition will be transparent and fairly liquid. Any water forms an emulsion that makes the oil milky. Dirt or accumulated wear from the TracLock plates will make the oil sludgy. In any case, I suggest you wipe out the floor of the housing with a clean rag and look at what's on the rag.

There should be a tag on the differential that describes the Jeep PN, the axle ratio, and the tooth counts. You can check that the tooth count on the tag matches the tooth count stamped into the edge of the ring gear, ie "41 11" = 41/11 = 3.73.The front ratio needs to be the same as the rear, numerically within a percent or so.

These Jeeps came with the 3.73 ratio standard and the 4.27 ratio optional. The 4.27s are more desirable today, but 3.73 is fine.

 

Nice link, thanks for the info! I'll crack'em and inspect, see what I got in there. I bought the gear oil but no ls additives.

 

Ok, popped the front diff and this is what I see. So, is this a Dana 30 w/3.73 (41-11) gearing? Looks like the ring gear was made in February 1973. Found just a few small metal frags in the bottom, gear wasn't that bad, but I totally destroyed the seal getting the cover off. It was stuck pretty good. Had to get a putty knife between it to get it to break loose. Back to Quadratec for a new seal. What should I use to clean the inside with?

-Troy

 

What I would do ...

I'd get a couple of new gaskets. I'd use a gasket scraper or stiff-bladed putty knife to scrape off all the old gasket. I would use some clean rags and wipe up all the milky oil and sludge or particles I could see. I'd put the cover on with a thin coating of gasket cement and fill the axle with oil. Then maybe 500 miles later, I'd change the oil again.

 

Thanks Tim! Sounds like a plan to me. I just ordered new gaskets, for the rear 44 too. Will probably hit the 44 tomorrow while I wait on the front gaskets to arrive. Appreciate the help!

-Troy

 

Glad I could help!

 

What Timgr said. I don't use gaskets any more though. I use good ultra black rtv only except on my trail Jeeps which I use a gasket and rtv on one side but not the other so they come off fairly easy in case of a trail fix needed. Many new vehicles do not use gaskets, just rtv. This has worked well for me. There are also the "Lubelocker" rubber gaskets that are reusable but kind of expensive.

 

Yep, saw the lublocker gaskets, got the cheap regular ones for the front and bought a lubelocker for the rear.

 

My truck has a lube locker type gasket on the auto trans pan. No drain plug , so you gotta pull the whole pan. If you do this more than once every 5 years, its totally worth it.

 

I'm not gonna be a heavy wheeler, so a lubelocker would probably be fine. Cracked open the rear 44, much easier to get the cover off of that one. It looks really good inside too. Would it hurt anything to squirt some Gunk up in there to rinse it out a little? I really can't get my hand in there with a rag to wipe it out, like the front. Figured Gunk would loosen some of the crud and rinse it out into my catch can.

-Troy

 

I use brake cleaner when I change differential fluid. Never had a problem before.

 

Every vehicleII have ever bought used, the first thing I ever did was to drain all of the fluids and inspect everything inside. Perhaps obsessive but at least I knew what I started with and it has't failed me yet.

 

Lublocker user here.. No leaks and re-usable.. No sillycon to scrape off either.

 

Ultra black and no gasket.

 

Paint thinner in a pump oiler will cost less than Gunk or whatever in a spray can. I would try to be rational and not obsess about cleanliness ... JMO cleaning something like this is more about your aesthetic sense than actually having some impact on durability/function/operation. Once you put clean oil in, it will churn like a dishwasher and pick up any foreign stuff. A little ATF is sometimes added to gear oil for differentials that need to be overfilled because of their orientation. Not only is ATF anti-foaming (the desired property in the overfilled case) but it also contains a lot of detergent. Run it, then change the oil.

 

Unca, you are exactly right and that is what I'm doing. Just bought the jeep and before running it regularly, I decided to pop both the diffs to see what kind of shape they are in and to change out the gear oil. So far everything looks pretty nice. I've got gaskets coming for the front and rear, one of which will be a lubelocker to try out. I should probably change out the diff bolts all the way around, with something stainless. I shot just a little Gunk in there as a rinse more so than a heavy cleaning purpose.

 

My diffs are back together, used a LubeLocker on both, new gear oil. I even painted both covers flat black and bought some grade 5 stainless bolts and washers. They look great! Moving on to windshield and dash panel work now.