Possible rear end problem... help me out.

BurningRubber · Jun 4, 2006

So ive been doing the normal general matenince over the period of time since I got my Mustang about a month or a little more ago. I changed the oil, and the trans fluid and checked over a bunch of stuff. Basically what I have left is plugs and fuel filter, and checking the diff fluid.

Today I had the chance to check the diff fluid, which I wanted to do soon because I have a slight whine coming from the rear when at highway speeds, not related to engine speed.

When I pulled the fill plug my jaw about dropped to the ground. There was around 1/2 of an inch of sludge built up on the plug itself. I thought, damn... and when I set it down I looked at my hand and noticed it was silver. I immediatly picked the plug back up and noticed that 1/2 of an inch of sludge was silver as well, and FILLED with metal shavings... wtf...

I dont know when the fluid was changed last, but it was a dark brown... nothing sick or anything, but the shavings and muck buildup really bother me. I talked to my bro who is a mechanic and he said its somewhat normal for the clutches to wear out in the LSD and of course come off as metal shavings... but thats fine and all, but the gear whine is what bothers me.

I need to pull the cover off when I get a chance, but dont know how soon thatll be.

Anyone have any input..? If worse comes to worst and the gears or bearings are gone... is it simple as a new set of gears, bearings, and a LSD rebuild/upgrade? If so then I guess its a good excuse to upgrade to better gears, haha. I want to figure this out before I start ordering other parts.

Thanks fellas.

Kilgore Trout · Jun 4, 2006

Change the fluid and inspect the gears ASAP.

Mike97gt · Jun 4, 2006

it's normal to have a metalic sludgy buildup on the fill plug...

You friend is right it's from the limited slip wearing and it's normal. Depending on your mileage you might want to change the fluid..

BurningRubber · Jun 4, 2006

94k, dunno if its been changed or not. It didnt look too bad itself aside from the shavings and sludge on the plug.

My brother said the only thing to worry about is the whine. Ive never had a vehicle with a limited slip rear, so im used to straight gear oil coming out, and if its gunked up or has shavings then you have an issue, haha.

I guess the plan is to pull the cover and drain it out, spray it out with brake cleaner, inspect gears and whatnot...

There is also a slight amount of play in the gears... but it didnt seem ecessive. Im starting to get the one wheel peel aswell. It will still spin both, but the tire with the least resistance will burn off for a while before the other one grabs if im not going in a dead straight line. I imagine the LSD is well worn.

Pennywise2 · Jun 4, 2006

I would change the diff. fluid anyway just so, you can
inspect the ring and pinion and everthing else.I had metal
shavings and oil on my drain plug the first time I changed
the diff. fluid after installing new gears it's perfectly normal.If you hear noises or whining coming from the diff.
than nine times out of ten your gears were installed incorrectly.You can also refill your diff. with Royal Purple.

BurningRubber · Jun 4, 2006

Its got the factory gears in it.

Definatly would go with a synthetic blend and the friction modifier.

Pennywise2 · Jun 4, 2006

Royal Purple has friction modifier in it already.

Mike97gt · Jun 4, 2006

if you are getting the one wheel peel then it's time for a limited slip rebuild..

there is two type of kits for doing this.

1. The pre shimed kit ( about 99 bucks) the benefit of this kit is it's pre shimed so the install is easy, the drawback is that you can't adjust the posi action a little tighter.

2. The basic kit ( about 44 bucks) the benfit of this kit is you can set it up a little tighter with the shims so you get a better posi action. drawback is the install is harder

alway remember to use as little friction modifier as needed to stop the chattering at slow speed turns.

Cobra Jay · Jun 5, 2006

The whine you are referring to could be caused by one of a few things.

1. Your pinion bearing is shot which caused your gears to wear pre-maturely (hence the extra metal on the plug- along with the L/S clutch pack being worn)

2. you could possibly have a bad axle shaft bearing or

3.your carrier bearings are shot which.

9 times out of 10 it's the Pinion bearing.

Reguardless of what caused it, your R&P is done.

I've had 2 R & P replacements under warranty (one TSB) in 2 of my 3 Ford trucks in the last 7 years and both times it was the pinion bearings that were at fault.

Like it was said before, your "One Wheel Wonder" is due to your clutches being worn out.

BurningRubber · Jun 5, 2006

The whine isnt overpoweringly loud, but I can hear it when im cruising down the highway.

How much on average is it to get a rear end rebuilt? I know it cost my freind around a grand or so to get a new one put in his Z71, but its two different vehicles were talking about.

Pearl02 · Jun 7, 2006

GT JAY said:
The whine you are referring to could be caused by one of a few things.

1. Your pinion bearing is shot which caused your gears to wear pre-maturely (hence the extra metal on the plug- along with the L/S clutch pack being worn)

2. you could possibly have a bad axle shaft bearing or

3.your carrier bearings are shot which.

9 times out of 10 it's the Pinion bearing.

Reguardless of what caused it, your R&P is done.

I've had 2 R & P replacements under warranty (one TSB) in 2 of my 3 Ford trucks in the last 7 years and both times it was the pinion bearings that were at fault.

Like it was said before, your "One Wheel Wonder" is due to your clutches being worn out.

One other thing to check is your tires. I just went thru this awhile back. I inspected everything and also had a tranny shop do a inspection. We narrowed the whine noise down to a couple of "cupped" tires. Just something else to think about. Pearl02.

hognutz · Jun 7, 2006

you need to inspect the gears. like above the whine could be tire wear or something.

pop the cover and look at them.

rear end rebuild pricing is about as follows

gears $140-170
install kit $100
31 spline axels if wanted $250
31 spline carrier $200-$450 depending on brand
trac lok rebuild if staying 28 spline $50

labaor $250-500 depending on shop and level of rebuild.

Yellow2002GT · Jun 7, 2006

You have the same problem I have right now.......! I just added more fluid to the diff and it took about have the bottle......the plug was sludge covered and had little particles in it....what happens is your limited slip clutches can were down to a point were there is a little play in the assembly and it can throw out your pinion bearing along with your gears.........If you have a stock rear end here is a suggestion......Buy a set of 31 spline axels...about 240....a good complete bearing set...100....and go to the bone yard and get an F 150 limited slip.. about 40 bucks.... and a new set of gears....about 140.....go the autozone and buy a limited slip rebuild kit may have to buy 2 because you want to put 4 clutches in the f 150 housing to replace the 3 clutches....You can rent the proper caliper to set the spacing..about .7 to .11 tolerence is optimal....and you could save about 400 bucks and have a rear end that will bite harder than you can imagine.....My buddie has done 2 rear ends like this soo far and both cars with slicks pull off the ground and are great for daily driving also...

"ED"

Possible rear end problem... help me out.

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