frequency differential fluid change ?

KJ79 · **Posted:** Sat Jan 07, 2006 6:33 pm

I was just flipping through the maintenance schedule B and realized that both front and rear differential fluids is to be changed as often as every 12,500 miles.
It strikes me as some kind of extreme frequent interval, that is at every 2nd oil change ! The gas model 3.7l calls for only 30,000 except for extreme use when it drops to 15,000 intervals.
Is DC worried the CRD torque will blow the diffs?
Anybody with a expert opinionon this?

LibertyCRD · **Posted:** Sat Jan 07, 2006 7:28 pm

Well I changed my wife's 3.7L KJ fluid in both diffs at 15,000 miles. The rear fluid looked nasty. The front fluid wasn't too bad. So personally, I wouldn't wait much past 15,000 mile intervals for any KJ regardless of engine. And besides, the engine shouldn't matter....all the rear ends are identical in these Jeeps. It is an expensive job if done properly so be prepared to pay big money for the synthetic fluid if you want to use that.

wenied · **Joined:** Wed Dec 21, 2005 4:01 pm **Posts:** 107

LibertyCRD wrote:

Well I changed my wife's 3.7L KJ fluid in both diffs at 15,000 miles. The rear fluid looked nasty. The front fluid wasn't too bad. So personally, I wouldn't wait much past 15,000 mile intervals for any KJ regardless of engine. And besides, the engine shouldn't matter....all the rear ends are identical in these Jeeps. It is an expensive job if done properly so be prepared to pay big money for the synthetic fluid if you want to use that.

My GMC sierra got it's first diff fluid change at 120,000 miles! lol...didn't seem to hurt anything

RedJeepCRD · **Posted:** Sat Jan 07, 2006 11:30 pm

Yeah, I noticed this diff fluid change thing in my manual to. It's the only vehicle I've seen that requires you change the diff fluid that frequently. I'm going to change mine at about 15,000 miles and use synthetic fluid. After that I'm only going to change it every 30000 to 40000 miles. It's just seems to be way to much cost to change them every other oil change. Gears $145, bear kit $90, setup 3 hours. Hummmmm.......

Fronts a bit harder, but it doesn't see the stress of the rear nearly as much. Maybe the is a lot of heat build up in the diffs. If that’s the case maybe a good finned aluminum diff cover would be a good investment.

Wes

KJ79 · **Posted:** Sun Jan 08, 2006 2:50 am

As I recall the manual for the CRD approves use of only a synthetic gear oil for the rear diff , for the front it does not specify synth. With the gasser you needed synthetic for trailer pulling duty only.
Has anybody come up with a mod for the rear diff cover - like some sort of quick drain. Would a front diff cover fit?
With the required frequency for fluid changes I think its a must to have a proper drain plug of sorts.

LibertyCRD · **Posted:** Sun Jan 08, 2006 8:21 pm

I agree...it is STUPID that Jeep engineers did not put a drain plug on the rear diff. The front diff has drain and fill plugs, thankfully. And they are real threaded plugs. All the rear has is a stupid rubber fill plug that leaks over time if not removed carefully.

Aftermarket diff covers are over $150 so it's not really justifiable.

I've heard you can buy a hand operated pump to siphon the old fluid out of the diff without having to remove the inspection cover. I might look for one of those when I go to do mine here in a couple of months.

grywlfbg · **Posted:** Mon Jan 09, 2006 8:25 pm

Wait... What? There isn't a drain for the rear diff? Sorry, I'm out of town so can't look at my KJ or check the manual. I thought this was a Jeep? I had the Dana-44 rear end in my TJ and both it and the front diffs had drain and fill plugs. So you're telling me I have to take the diff cover off (taking an oil bath in the process) just to change the fluid? How is it refilled? Are they insane?

In my TJ I replaced the xmission, xfer case and diffs w/ Red Line synthetic at 30k miles and was planning to change it every 60k but sold the TJ to buy the KJ before that interval.

Don't get me wrong, I bought the CRD so I'd have a new technology to learn (never had a diesel before) and I like puttering in the garage but this seems ridiculous.

As for a hand pump, Amsoil makes a pump primarily for filling diffs and xmissions but could possibly to be used for removal. Can't tell form the picture but maybe one could run a tube from the suction side into the diff?

https://www.amsoil.com/storefront/g2039.aspx

I haven't used one but after rigging up a funnel w/ a length of silicone hose tied to a ladder to doing my TJ fluid change I'm planning to invest in one.

kevh · **Posted:** Mon Jan 09, 2006 9:51 pm

rear diff fluid swap becomes a bit more important with a lsd. without changing the friction modifier often, the lsd can get grabby and start locking up, causing premature wear, heat, and often failure.

oldnavy · **Posted:** Mon Jan 09, 2006 11:39 pm

'06 KJ's don't have LSD and it was option on '05 models with probably most not having LSD either. The suction pump things can be found at Wal-Mart and autoparts stores like AutoZone and can be used to suction out the oil, but the removing of the cover plate will drain the oil better then the hand pump. It's really not that hard to do, use to do it on the '87 Cherokee every other year to make sure no water got in differential.

Oberkanone · **Joined:** Thu Oct 06, 2005 2:34 pm **Posts:** 26

Service interval for changing front and rear differential fluid is:
every 12,500 miles for diesel
every 30,000 miles for gasoline engine
Huh? What does diesel have to do with diferential fluid?

KJ79 · **Posted:** Fri Jan 13, 2006 12:15 am

This is all good and well....back to "square 1"

Oberkanone's post above repeats precisely my question that launched this thread!

[/quote]Service interval for changing front and rear differential fluid is:
every 12,500 miles for diesel
every 30,000 miles for gasoline engine
Huh? What does diesel have to do with diferential fluid?

How much sense does this make?

oldnavy · **Posted:** Fri Jan 13, 2006 9:53 am

KJ79 wrote:

This is all good and well....back to "square 1"

Oberkanone's post above repeats precisely my question that launched this thread!

Service interval for changing front and rear differential fluid is:
every 12,500 miles for diesel
every 30,000 miles for gasoline engine
Huh? What does diesel have to do with diferential fluid?

How much sense does this make?[/quote]None, but neither does 6500 mile oil changes with a good synthetic oil in the CRD Liberty.

grywlfbg · **Posted:** Fri Jan 13, 2006 3:07 pm

Well, remember we're talking Schedule B here - the harsh environment maint. schedule. Someone w/ a manual handy - what's the Schedule A interval? Perhaps they assume that CRD owners will be doing more towing? The increased torque of the CRD over the gasser will cause more wear on drivetrain internals?

Idk, chaning diff fluid w/ every oil change seems a bit extreme to me. I don't have the LSD rear end so I'll do my first change at 15k and do it every 30k after that w/ synthetic fluid.

I've long been a Redlin fan for gear oil (have used it in my RX-7 and TJ) but since I'm part of the Amsoil borg now I guess I'll try them. Anyone have any feelings on Amsoil's gear oil?

oldnavy · **Posted:** Fri Jan 13, 2006 3:21 pm

Anyone know of after market replacement with drain plug?

gsbrockman · **Posted:** Fri Jan 13, 2006 7:47 pm

oldnavy wrote:

Anyone know of after market replacement with drain plug?

http://www.yourcovers.com/newdifferential.htm

Not real up-to-date as far as what diffs the CRD has, but it may be a start.
Greg

KJ79 · **Posted:** Wed Jan 25, 2006 3:41 am

Would anybody be interested in a rear diff mod so the fluid change every 12,000 miles could be done without removing and resealing the cover?
If there is sufficient interest I might be able to get a local fabrication shop with a CNC plasma cutter to get us a solution. Essentially this would be a metal spacer sandwiched between the diff and the existing cover. The bottom of the spacer will feature a Allenkey type drain screw/plug, which will be recessed so you will not damage it on the trail. Another option might be to integrate a partial rear diff cage (rock protection). The whole affair will be installed with gasket class RTV sealant (once only!) and extra length bolts as required.

breakerbacker · **Joined:** Wed Dec 07, 2005 1:23 pm **Posts:** 76

This sounds like a good idea. Another benefit may be a little longer period of time between fluid changes as a result of the increase in fluid capacity.

grywlfbg · **Posted:** Wed Jan 25, 2006 1:08 pm

I'd be interested in this. I do a lot of towing so plan on regular changes. I also like the idea of more fluid in there. Would there be another on top for filling (though that could make overfilling likely)?

oldnavy · **Posted:** Wed Jan 25, 2006 2:13 pm

grywlfbg wrote:

I'd be interested in this. I do a lot of towing so plan on regular changes. I also like the idea of more fluid in there. Would there be another on top for filling (though that could make overfilling likely)?

It already has a fill plug man, how else would you get fluid in the thing. :wink:

I would be interested in a proper replacement cover with a drain plug.

LibertyCRD · **Posted:** Wed Jan 25, 2006 2:18 pm

There is very little room between the inspection cover and the fuel tank as it is. A spacer of any kind would be a bad idea IMO. I want a replacement cover with a drain plug.

frequency differential fluid change ?

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