Rear end???

[ArkansasMystic]

I'm having troubles with the rear end of my car. When I drive a pretty good distance (100+ miles), my rear starts squeaking/grinding. It doesn't do it when going strait, only when you're turning pretty sharp. Also, the guy I use to work on my car noticed something he said was odd. When the rear is lifted off the ground, brakes off and car in neutral, the rear tires still won't freely spin. He said that they should do that. He also said there's a little slack in my rear. I'm wondering what can be going on. First I thought the rear is going out, but I'm also wondering if it isn't the posi-track (or is it limited slip, either way). Any ideas?

[evasbird]

try lifting the rear up like you said but with the calipers removed. maybe its just a slightly warped rotor or a caliper that isnt releasing all the way and making it hard to rotate the wheels. any groves is the rotors? my front wheel on 1 side was hard to rotate cause the rotor had some bad groves in it, had it turned and is fine now.

[ArkansasMystic]

The rotors and pads on the rear are about 7 months old. My mechanic first noticed the issue when replacing the old rotors.

[Bigjht]

Grinding to me sounds more like the rear gears instead of the differential. The squeaking could be the bearings going out as well. Either of which could potentially cause the wheels not to spin freely if going bad. Next time have him take the rear cover off the rearend and check the wear pattern on the gears. If they're off enough to cause grinding I would imagine it would be noticed fairly easily.

[adam2kgt]

The squeaking around a sharp turn could be the clutch packs in the differential letting their presence be known. If your car has a lot of miles, or has had the fluid replaced without having friction modifier added, it will cause the rear clutches to make some noise. Noticed any loss in the limited slip action? As far as the rear not wanting to spin, I would suggest having somebody start with pulling the axles and checking to see if the diff spins free, if it still binds, pull the carrier out of the housing. If the pinion spins free, bad carrier bearing, if the pinion doesn't, bad pinion bearing.

P.S. As far as the rear tires spinning freely, it's a matter of what his opinion of freely is. Keep in mind, when you turn a Mustang rear wheel, you are turning the whole diff, the other wheel, and the driveshaft, or you are turning the clutch packs if the other wheel isn't spinning. That is a lot of friction, especially compared to the rear wheels of some vehicles, front wheel drives in particular. Not doubting your mechanic's knowledge, just giving you a little insight. And a little slack is normal, otherwise it would bind after heating up. Do you notice any clunking going from 1st to reverse? Like a metallic "clunk" when you back up, then drive forward, or vise-versa?

[stumbaugh]

Preston get ahold of me any day next week and we will figure out what's wrong with it. I got laid off Friday so I'm free.

[ArkansasMystic]

Adam, yes there is a clunk when I begin to back up. I've not noticed any problems with the limited slip. I know when you break the tires loose you'll definitely feel the back end sliding/fishtailing. The tires wouldn't spin at all best I can remember. What I'm hoping will fix the problem is buying new gears along with an install kit that includes the bearings, that way I can get some more added punch and also have the car up and running. The car does have high miles, almost 135k at the moment. The guy that I always use to do the work on my car is a certified GM tech. He works at the local dealer and does great work. He admitted he wasn't real familiar with the rear ends, so he just said that seems odd and if it was him he'd have it looked at. Jake, are you free Thursday? I'm off then and might can make it over there so we can take a look. Thanks guys!

[adam2kgt]

Yeah, with enough slack in the rear to give you a clunking between gears, I'd bet you need new ring and pinion. Gotta love the way Ford designed our rear ends to eat themselves slowly over time! While you have it apart, though, if you could afford new clutches, now would be the time to rebuild the limited slip. Throw a few extra clutch disks in for a tighter limited slip action, and you shouldn't have to worry about it for a while.

[stumbaugh]

Ya I'm free Thursday. Just call me. The clunk sound could also be a u-joint and the sound it makes when u turn could simply be that the differential is staying locked in the posi-trac position. And the rear tires dragging sounds like a brake problem.

[Joey5.4]

Gotta love the way Ford designed our rear ends to eat themselves slowly over time!
It be more people not setting rearends up correctly than the way Ford designed them. My dad 88 GT has ove 300k miles on it and has original clutches if differential and original ring and pinion, he has never had a problem one out of it.

[ArkansasMystic]

I'm thinking its something with the limited slip. I just noticed today, the rear passenger tire has a lot more wear than the driver's rear. I would assume they should be about the same, so maybe I am 1 wheeling and not realizing it. I guess the plan from here is to have Jake take a look Thurs with me and see what we can find. Jake, have you changed your number or is it still the same? What time's good for you (I got all day)? If I'm gonna have to have the rear worked on, I wanna do it right (but keep it reasonable). If I need new gears (forgive my ignorance, but isn't that the ring and pinion?), I'll probably step up to 4.10's. I can get that with the install kit which should come with all the bearings, then add a limited slip rebuild kit if needed. I think it's like $160 for FRPP 4.10's, $70 for the install kit, and $125 for the limited slip rebuild kit. Not sure what installation would cost, but for the money I'll buy the parts needed to fix the rear so it'll be good for many more miles to come. Thanks guys, appreciate the help.

[stumbaugh]

My number is 479-970-1373. Any time Thursday is good for me.

[ArkansasMystic]

Jake, you've got a PM.

[ArkansasMystic]

Ya I'm free Thursday. Just call me. The clunk sound could also be a u-joint and the sound it makes when u turn could simply be that the differential is staying locked in the posi-trac position. And the rear tires dragging sounds like a brake problem.

This to me makes the most sense. The tires may just be extremely hard to turn by hand because the rear's staying locked in. I also get the clank on a hard downshift (i.e. going 50, downshift to third and punch it to pass a car), or every once in a while when I brake real hard. Either way, I just need to know what I HAVE to have to get the problem fixed, then what I need to add while I'm in there. I'm sure Jake and I will know something Thursday though for sure.

[adam2kgt]

I highly doubt it's your problem, but I had a similar clunk in my car after switching back to stock gears from 4.10's. The lesson I learned, use Blue Loc-Tite on the driveshaft bolts, cause even bolts that look and feel tight, can loosen if nothing else is helping hold them in place.

[ArkansasMystic]

Funny you mention it. I have actually had trouble with the driveshaft bolts. They tend to come loose. I had them tightened and it seemed to help the clank (didn't have the other rear end noise at the time). However, it didn't last long. I'll add that to the to do list for Thursday when Jake and I look at it. I spoke with a rear end specialist in the area, he seems to think there's no problem with the car, I just need to change the grease and add some friction modifier. He almost would bet on that being the problem. We'll find out though, I really hope that's it.

[Blackjack]

Hey, I'm still new here, but I've rebuild a ton of the stock trak lock's. Which the one I've got in my car is a 31 spline style.

Anyhow, if it is perfectly fine straight no noise what so ever, then it pop's on a sharp or just a turn in general, then it defiantly could mean the unit needs to be rebuild.

If the clutches get weak, and the S-spring gets weak, what happens is, in a turn the spider gears start to bind. Hence the popping sound. Course if that's it, drive it long enough and it will damage the spider gears.

[backfocus]

Might also be good to check the upper and lower control arm bushings. It sounds like you have other problems in the housing, but it would be good to check those while you are at it. When extra outward force (such as in a turn) worn bushings will cause the rear to move more than normal. At the age of your car, is about the time they go anyway. Plus they are fairly easy to replace.

[Jeff2000GT]

I had a similar issue in my car, it had been doing it for literally years and I got sick of it so I bought a new ring & pinion, all new bearings and a posi rebuilt kit and had my mechanic install it.. bingo problem solved.. from what you describe it does sound like one of those 3.. if you're going to fix one might as well do all 3..

[ArkansasMystic]

Thanks for the reply. I guess I failed to update this thread. I ended up selling the car as is in August 2009, so I never tried to fix this. You're right though, everything I've read lead to one of those three, and it was gonna be best just to do them all at the same time so it'd be fresh (also wanted 4.10's or 4.30's instead of 3.73's).