Differential oil

Johnboy · **Posted:** Wed Oct 03, 2007 1:41 pm

I know it needs to be done every 15K

I know it needs synthetic

I know it is expensive

But what make/weight should I use? What are the torque specs for the rear diff cover?

Thanks....

JR

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

I just did mine.

It needs to be done at 12,000 miles according to the book (gear break in). Beyond that, I think the interval can go quite a bit longer (30k or so if you use good components.)

Book calls for 75w90 front and rear (unless you tow, in which case go with 75w120 in the rear). I did Mobil1 75w90 front and 75w120 rear... pricey, but it should last quite a while.

Based on advice from this board, I ordered a Lubelocker reusable gasket for the rear differential (order the 8.5 inch Chrysler model). From the factory it is sealed with crappy orange RTV (big pain in the booty to get off). The Lubelocker instructions said to torque the diffy bolts down in two stages, going for 15 pounds first then locking them at 35.

Hope that helps.

Johnboy · **Posted:** Wed Oct 03, 2007 2:10 pm

Cheers, off to the parts store....well maybe this weekend. Thanks again.

SCKJCRD · **Posted:** Wed Oct 03, 2007 3:23 pm

I used Mobil1 75w90 in the front, 75W140 in the rear. If I remember correctly, the front takes somewhat less than 2 quarts, and the rear takes a little over 2 quarts. I bought two quarts of each, and used some of the leftover 75W90 to "top off" the rear. I also used a "marine oil change pump" to suck the old grease out of the rear axle through the fill hole. No gaskets or RTV needed, since I didn't remove the cover.

Johnboy · **Posted:** Wed Oct 03, 2007 4:11 pm

SCKJCRD wrote:

I used Mobil1 75w90 in the front, 75W140 in the rear. If I remember correctly, the front takes somewhat less than 2 quarts, and the rear takes a little over 2 quarts. I bought two quarts of each, and used some of the leftover 75W90 to "top off" the rear. I also used a "marine oil change pump" to suck the old grease out of the rear axle through the fill hole. No gaskets or RTV needed, since I didn't remove the cover.

I am no mechanic, but i would think this method would not remove the metal bits, and would prevent a good cleaning with brake cleaner? Guess, the early mileage fluid changes would be the most important to actually open the diff. I am at 26K and do not know how many times mine has been changed (2nd owner, no DC service records of diff oil change)

0311_DoC · **Posted:** Wed Oct 03, 2007 4:40 pm

yes for us non mechanic types how hard is it to change? what tools do we need? im scared to death im gonna mess this up..... :oops:

Anomious · **Posted:** Wed Oct 03, 2007 4:50 pm

http://www.getahelmet.com/jeeps/maint/diff_fluid/

Instructions with pics! LK

0311_DoC · **Posted:** Wed Oct 03, 2007 4:55 pm

Anomious wrote:

http://www.getahelmet.com/jeeps/maint/diff_fluid/

Instructions with pics! LK

Cool thanks

Johnboy · **Posted:** Wed Oct 03, 2007 5:16 pm

Should be fairly simple, care should be taken when putting the diff cover back on. ie. go in stages and get it even, and end up at the right torque.

BankNote4X4 · **Posted:** Wed Oct 03, 2007 10:50 pm

Isn't the torque 15 on the 1st time installed then 35 when reused?

Cowpie1 · **Posted:** Wed Oct 03, 2007 11:44 pm

BankNote4X4 wrote:

Isn't the torque 15 on the 1st time installed then 35 when reused?

One can become too "anal" about bolt torque on the pan. I have done the diffs a number of times, and reused the lubelocker gasket with good results. I just "snugged" up the bolts in order, then went around the order again applying a more firm application. I have NEVER used a torque wrench on a diff pan in my life and have NEVER had a problem.

I may not be entirely uniform in the torque, but since I have done this type of procedure for over 4 decades, I am confident that the results are uniformly good. I have NEVER had a leak from my diff, NEVER had a damaged gasket, and Never had a damaged pan.

So.... don't become over exited about not getting each and every bolt exactly equal to the minutest detail. We are not talking about a head gasket here. That would be altogether a different issue and torque would be critical.

Just enjoy the experience of doing your own work and the satisfaction that comes from that (not to mention the money saved). I am sure there are some here that will take exception to what I have said, but that is ok. :roll:

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

The Lubelocker instructions direct you to torque down the bolts in a certain sequence to 15 pounds, to avoid warping the cover. Then it says to go back and lock them down to 35.

Worked for me.

And I meant 75w140 for the rear, no idea where the 120 came from (no caffeine this morning).

One word of warning, the bolt heads themselves are kind of soft, and it is hard to get a long torque wrench up behind the gas tank to reach the top ones. Be careful your socket doesn't slip off and bung up the bolt head.

MRausch82 · **Posted:** Tue Oct 09, 2007 5:58 pm

I am going to change my front and rear diff. oil tomorrow. I bought Mobil 1 75w90 for the front and Mobil 1 75w140 for the rear. I am going to be towing a Uhaul trailer 5 hours tomorrow PM. I am not super thrilled about the RTV sealant, so I went on NAPA's website and they showed a gasket for it. Any reason not to use that gasket? If I cannot get the gasket in time and have to use RTV, will it hurt it to drive it that far after sealing it up? I checked the Permatex chart at Pep Boys and it says to use Ultra Blue for the rear, however, when I called Permatex, they asked if I was using synthetic (which of course I am) ans they said to use the gray stuff, not quite sure why as they did not tell me. I am thinking I will just take it to my buddy in the AM and let him do it, but I am still concerned about the long drive and the possibility of a leak, thats why I like the idea of the gasket NAPA offers....

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

I just changed my rear end fluid with Royal Purple 75w 90 and I used the permetex grey gasket material and it went very smoothley. Then I changed out the front differential with the same royal purple 75w90 then I went out on the highway to run it a little bit and it was so quiet I could not believe my ears it was like a completely different vehichle so nice and quiet. I was in my local car quest parts store and mentioned the quiet results I got from the Royal purple and asked him if he had ever heard of anybody having the same results and he said all the time and that some dodge dealers are starting to stock the Royal purple gear lubricant to quiet down rear ends on certain vehicles. Just passing on my experiance. Hope it helps some of you.

JJsTJ · **Posted:** Wed Oct 10, 2007 7:55 am

FYI on Royal Purple and some other syn gear oils:

Some very interesting info on various name brand gear oils including failures by some "respected" brands.
http://www.amsoil.com/products/gearlube ... Paper.aspx

Highlights:

Failures by the following after shear testing:
Lucas 75/90
Penzoil Syn 75/90
Mobil 1 Syn 75/90
Penzzoil Gearplus 80/90
Mopar Syn 75/90
GM Syn 75/90
Royal Purple syn 75/90 (Started too thick for its viscosity And ended up too thick!)
Torco 75/90

Failures of Brookfield test:
Redline
Royal Purple
Lucas

1TDI4Me · **Posted:** Wed Oct 10, 2007 11:47 am

I did mine last weekend. The front is easy with the drain plug. The back is less convenient since the
rear case cover needs to be removed. Why no rear drain lpug at the low point? It would be a lot
easier.
Also, putting the thick oil back in is a pain in this rig. My hands were very fatigued from squeezing the bottles
and the fill hole is too high to just put the oil in directly from the bottle. I uses a bit of clear tubing to extend it.
Anyone know an easier way?

MRausch82 · **Posted:** Wed Oct 10, 2007 2:28 pm

1TDI4Me wrote:

Anyone know an easier way?

Use a fluid transfer gun aka syringe. That works well. Have not tried it on the Jeep. I will be towing a Uhaul in a few hours. I did not get a chance to change the oil today

JJsTJ · **Posted:** Wed Oct 10, 2007 5:04 pm

Amsoil Bottle Pump works well for me.

stump doctor · **Posted:** Wed Oct 10, 2007 6:37 pm

On my last change I used a "'suction gun" from agri-supply ~ $10.00 worked great with a clear flex hose

1TDI4Me · **Posted:** Wed Oct 10, 2007 10:48 pm

Thanks for the suggestions. One of these devices will make things
a lot easier and speed up the process to boot. I won't be dreading
the project the next time it comes up.

Differential oil

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