jeepcherokee99

So I had my transmission rebuilt about three years ago. I just had my rear differential and transferase rebuilt about a year and a half ago. During that time I asked the mechanic to change the front differential fluid. He checked said it was good and left it alone. I trust this mechanic he has done a lot for me. I just noticed a rear seal on the transferase was leaking and took it in to get replaced.



Now he tells me he hears grumbling and growling noises in the front diff.

What are causing all these problems? I baby this jeep. It's a 99 WJ LIMITED 4.0 with only 118k. I don't even have a hitch on it, it didn't come with the the tow package so it has never even towed a thing. I want to know what causes these problems so I can prevent them from happening if that's even possible I guess...

How long can I go without rebuilding the front diff? Can I just change the fluid more often and run it?

dave1123

The transfer case seal is a normal wear item. You can polish the sleeve of the driveshaft to help seal it. If there is a wear groove in it, you might consider replacing it. Every time you go over a bump, the sleeve slides in and out. When the rusted part slides into the seal, it helps tear it up.

Try pulling the front diff cover and inspecting the gears. Adding a friction modifier may help extend it's life.

jeepcherokee99

What's a friction modifier?

jnicewan

Its the addititve you put in a limited slip differential. It basically makes the fluid "slicker" to allow limited slip clutches to slip and not bind. Adding something like this may not help at all but if anything it might prolong the life slightly.

Was the mech confident the noise was inside the diff? Could it possibly be from a wheel bearing, u-joint or driveshaft etc?

jeepcherokee99

Ya he was confident. I dnt have U joints. He already rebuilt my transmission, Transfercase, and rear diff. So how long can I go before fixing this? Will it cause damage to other things?

jnicewan

It really depends on what is causing the noise. Most of anything inside a diff will eventually cause more damage the longer you wait and eventually it could cause complete destruction of the complete axle.

Im not trying to scare you into replacing anything now but without knowing specifically whats causing the noise it would be difficult to assume what might be wrong with it and how far it will make it. Some people get by with noises for years and others might only last days or weeks.

Bustedback

New boat payments will make a mechanic's ears more sensitive and customer's vehicles in need of expensive repairs.

jeepcherokee99

Lol. I had the rear diff bad and I can hear the same noise in the front around 30-50 mph so I know it needs to get repaired eventually.

JBimmolate

All the diffs with aluminum housings tend to get bad bearings due to the differences in expansion rates between the steel parts & aluminum parts. Also is your jeep AWD? If so running different brand or tires with different wear can cause the front diff to cook itself due to the 2 axles turning at different speeds. The smaller diff (front) will fail before the larger (rear) one.

Miles

dave1123

IMHO, pull the cover and eyeball it. Check for "silver" fluid caused by bearing deterioration, spauling on the gear teeth, backlash, whatever. My rear axle whined for 2 years before it started growling, then I knew it was finished.