Fruid

Trying to sort out a problem of a noise coming from the rear end of my 2000 4.0l XJ. It sounds like binding brakes but they are fine so I think it must be the diff. I have a Dana 35c and Selec trac trans.
Pretty sure its not the UJs on the drive shaft as it only happens when after about 10miles of normal driving (when things have warmed up) and the UJs feel fine. Get it when stopped and pulling away from a junction or lights.
Could it be a lack of additive in the Diff? Anyone know what the symptoms of this would be.
The Jeep is fairly new to me and I haven't changed the diff oil just checked the level which was good.

TheJerm

Lack of additive in the diff just causes the limited slip to wear out and not work. Is the sound like a clunk when your pulling away from a stop?

dogger15

Prob time for a new axle

TheJerm

A slight noise means new axle

mjs302

Limited-slip additive is a friction modifier that allows the clutches in a limited slip diff release smoothly. Without it you can get a "chattering" noise, but that would only happen when the tires are traveling at different speeds (such as when turning). If you have the noise while driving in a straight line, this is not your problem. Limited slip additive is only required in diffs that use clutch material (Trac-lock etc) . It is not required for open diffs or lockers (except some E-lockers).

rrich

Try adding a tube of it - they can clunk even going straight. Clutches sticking then releasing.

Too much won't hurt a thing. The additive wears out after about 100,000 miles.

LET US KNOW HOW IT FARES.

Fruid

The noise only happens whilst turning out of a junction left or right, when going in a straight line the whole car is very quiet and smooth.

I will get some additive and new oil and change it over and let you know how i get on.

Thanks everyone.

rrich

Caution - some of the diff oils SAY they have the slippery stuff already added. It's usually not enough. Add a tube anyway - it won't hurt anything but it may prevent you from spending unneeded time and money.

Currie -the makers of great performance axles and diffs won't warranty them if synthetic oil is used. Does that tell you something?
They say synthetics don't carry the heat away, causing the gears/bearings to overheat. Use old fashioned dinosaur oil.

Fruid

Ok guys here it is...

I drained the old oil out of the rear diff(it was black) , let it drip for about 4hrs (its cold in Scotland just now). Cleaned op the faces and while waiting I cleaned up the cover and resprayed it with a fantastic underseal I use.
I refilled with 4oz Torco LSD modifier (F) and then to the fill level with Castrol Syntrax 90w-140 LSD oil.
Took it for a long run and I guess what?? NO MORE BINDING NOISE.

I am so pleased as I thought the diff was goosed

djb383

With a double dose, the clutches r so slippery now that it probably performs like an open diff. LOL, just kidding.

Fruid

Yes the noise was like a clunk, followed by a creak much like a handbrake being left on but only when turning and pulling away from a stop after about 20mins driving.
Not now though!

rrich

The clutch material is "sticky." The additive keeps them from sticking too much. They have trouble releasing without the slippery stuff.
The additive is minimal in gear oils, even though they say it's for them. And it wears out.
"too much", within reason, won't hurt anything or cause them to slip too much. 1 tube is not even near "too much."

You have to add another tube every 20-30,000 miles - otherwise the lack of it wears the clutches very fast.
The "clunk" - it's trying to self destruct. Sticking together too long, then suddenly releasing (clunk) literally tears the clutch linings off the discs. Then the pieces get into the bearings, tearing them up.

Take one apart and see how they work.

Fruid

I might have to take it apart if its been damaged driving like this. There was no material in the old oil! Is that a good sign that the linings haven't been ripped off?
Changing the subject slightly, what does the lever in the cab do to the transfer case when you select "4wd Part Time". Does it just join up the front and rear axles?

TheJerm

The clunk I was referring to above is wear on the slip yoke and tcase output, pretty common and easy to remedy by packing the slip yoke with grease, just FYI.

4wd part time is true 4x4
4wd full time is like awd but not built to be like true awd cars.

Assuming you have both you have the np242, great winter tcase

rrich

Germ - but you suggested he get a new axle when you hijacked the thread!

Obviously if it's something else - FIX THAT!