diff noise

[timothy100]

I just installed a new diff in my eta (3.73 LSD) with only around 110k miles, and when I turn the wheel at low speeds around 10-15 mph it makes a very noticable clunking/vibration sound. It sounds like something is rubbing or hitting something. It doesn't matter which direction I turn the wheel, and only happens at low speeds.

Any ideas what it could be? I'm hoping its not the differential as I just spent a chunk of money on it. Could it be the oil I used in it? I used some generic NAPA 90 weight.

Any help is appreciated, thanks...

[Den]

For an LSD, you need to mix a friction modifier with regular gear oil. Most folks just use Redline synthetic gear oil that already has the friction stuff in it.

http://www.redlineoil.com/products_gearlubricants.asp?pvID=81&prodID=60&subcatID=20

[timothy100]

Ahhh didn't know that. Thanks. So without a friction modifier it would make clunking noises and vibrations?

[Den]

The sound of running an LSD without friction modifier is usually described as 'chattering' rather than 'clunking,' but yes, it will make noise. There may well be someting wrong with your diff, but running the proper lube is the first thing to try. You can get LSD friction modifier additive in a can and add it to your generic gear oil, but I'd pony up the $15 for 2 bottles of Redline.

[BimmerKris]

o cool, mine does the same thing

[BimmerKris]

How was the differnce with the new diff. I have been wanting one for a while, is it worth it

[timothy100]

The difference between the stock 2.93 diff and the 3.73LSD is incredible. I would not reccomend it at all if you do very much highway driving, but if you want to be fast off the line or around town it makes a big difference.

[DTRguy]

I bumped this up because I searched and found out that someone else is having basically the same issue as I. During slow turning there is an unloading and loading that can be recreated when both wheels are off the ground and one held while the other turned. Best way to describe the sound as a "honking" sort of sound. Almost as if the clutch plates are sticking intermittantly. It doesn't smoothly differentiate. I think that maybe yeah, I don't have the right oil in it... but isn't cheap oil ...Motul Gear 300 75/90 gl5. But couldn't tell if it has any specific Friction modifiers. Is it something that will go away (the noise)? Anyone have any other advice for a gear oils that can be had locally? Redline isn't easy to find at your local parts store. TIA!

[BahnE30]

go to the local ford dealership, ask for friction modifier, it is the best stuff on the market hands down, i cooked the clutches in my rear end, like fused them together so it was like running a locked rear end, dumped a bottle of that stuff in, free'd them up, but the rear end was toast, got me by for a couple months.