front or rear diff gears gone bad

JeepPilot · **Posted:** Mon Mar 08, 2010 7:20 pm

I have an '02 Limited. Recently, when I pull it into 4HI or LO, there is heavy grinding/rumbling sound and turning to the left or right feels very limited. Thought something was wrong with my transfer case, took it to the dealer. They told me that my tcase is full of fluid and just fine, but the tech noticed that the front or rear differential gears have gone bad. He told me it'd be about 4-5 hours and $500 worth of work just to tear 'em down and find the problem.

so here are my questions -

a) Does this sound reasonable? I don't want to drop a ton of money and get taken to town by the dealer.

b) Am I going to be fine driving with potentially bad differentials gears? Or is it going to be a dangerous catastrophic failure down the line?

InCommando · **Posted:** Mon Mar 08, 2010 8:04 pm

RUN if they can't narrow it down from there!

Off the top of my head I'd guess a hub or a rack.

JeepPilot · **Posted:** Mon Mar 08, 2010 8:14 pm

as in narrowing it down between front or rear diff?

LibertyFever · **Posted:** Mon Mar 08, 2010 8:38 pm

That sounds like an awful vague answer from a dealership. Just because the tcase is full of fluid doesn't make it "just fine".

New diff gears would cost you a minimum of $500 just in parts, then there's labor at dealership rates.
I say get a second opinion from another garage.

From your description I have to hazard a guess that there is a problem with the front diff only, maybe a bad pinion gear bearing that grinds only under load (in 4WD). You should be able to continue to drive in 2WD.

JeepPilot · **Posted:** Mon Mar 08, 2010 9:41 pm

LibertyFever wrote:

That sounds like an awful vague answer from a dealership. Just because the tcase is full of fluid doesn't make it "just fine".

New diff gears would cost you a minimum of $500 just in parts, then there's labor at dealership rates.
I say get a second opinion from another garage.

From your description I have to hazard a guess that there is a problem with the front diff only, maybe a bad pinion gear bearing that grinds only under load (in 4WD). You should be able to continue to drive in 2WD.

So will I be ok in 2WD, or is this something that's just going to fall apart over time and affect me even if I decide not to fix it right now?

Jeepjeepster · **Posted:** Mon Mar 08, 2010 10:49 pm

Probably the front driveshaft. Never use 4hi or 4low on paved surfaces and NEVER go back to that dealer.

If its the front driveshaft its fine in 2wd but if the shaft gets bad enough it could simply fly apart.. Destroying lots of expensive stuff a long the way.. Best to get it checked out.

Here ya go..

http://www.jeepkj.com/forum/showthread.php?t=43950

JL Rockies · **Posted:** Mon Mar 08, 2010 10:51 pm

There's nothing wrong with using 4 HI (Full time) on pavement.

Donkeykong · **Posted:** Tue Mar 09, 2010 12:15 pm

JL Rockies wrote:

There's nothing wrong with using 4 HI (Full time) on pavement.

Yes there is.

Unless you have the AWD version of the transfer case (I can't remember if that is select-trac or command-trac) you will "spool" up the transfer cas because the front axle has a slightly different axle ratio than the rear.

Some guys have forgotten their Libby was in 4hi and taken it down the road for 70+ miles and all the sudden *bang* bye bye front diff.

BVCRD · **Posted:** Tue Mar 09, 2010 12:49 pm

^ You beat me to him.

Donkeykong · **Posted:** Tue Mar 09, 2010 1:57 pm

Now I see it.

Missed the full time bit.

dieselenthusiast · **Posted:** Wed Mar 10, 2010 12:48 am

JeepPilot, how many miles do you have on your KJ? When was the last time you changed your gear lubes or transfer case oil?

InCommando · **Posted:** Wed Mar 10, 2010 12:48 pm

JeepPilot wrote:

as in narrowing it down between front or rear diff?

Yes. They are pulling your chain if they cannot tell which it is if one does have a problem.

front or rear diff gears gone bad

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