Rear end clunk

[seanpmoney]

So I have an 03 GT with only 58k original miles, I got this car about a year ago with factory wheels and tires. I wanted to upgrade to a meatier tire because its supercharged and has a 4.10 rear; I couldn't get any traction lol. Got myself some nice new wheels and wider tires for the rear and then all of a sudden when I took it on a joy ride to test out fitment, after about an hour I had some NASTY clunks coming from the rear end anytime I turned at all. Limped it home to find out my diff had a pretty bad leak (also found out my car doesn't have quad shocks with factory upper and lower control arms), wasn't particularly low on fluid but it was certainly leaking. I replaced the diff seal and put the proper amount of Royal Purple fluid (with friction modifier in it) into the rear end. So that fixed the very aggressive clunking whenever I turned going forwards. About 5 months go by with no notable issues but about 2 months ago, I was backing into my driveway and i started hearing and feeling a similar clunking from the rear end; and only when i was turning. This clunk sort of comes with each revolution of the wheel and its a pretty nasty feeling. I must note that i only hear/feel it after I've driven the car around for a significant amount of time and gotten everything up to temperature which leads me to believe its not a mechanical failure, It wont do it at all when i first back out of the driveway or if I just take it for a short cruise and back it into the drive. It only really does it when I am going in reverse generally. Additionally i must note when I am riding the clutch while turning in reverse its not too bad but as soon as the clutch is depressed I can feel the whole rear end sway almost-- terrible feeling! My thoughts are bad rear upper and lower control arm bushings??? I'm curious if anyone else has had this issue or has any insight for me; Thanks!

 

[I_LIKE_TURTLEZ]

The differential vent tube is dirty, that's why it went from seeping to full on leaking quickly.
Whoever installed the 4.10 gear set probably didn't do it properly, possibly a pinion bearing or wheel bearing since you lost your oil(which I doubt they replaced).
Another likely culprit is a bushing or u-joint but you would notice these at speed at all times, not just when hot.

Reverse turns the rear end the most so I'd suspect the pumpkin is toast(Happy Halloween)



Really your biggest problem isn't the cooked rear end, it's the fact someone threw a supercharger on your cast 2v engine. That's an expensive mistake.

 

[seanpmoney]

If it was a substantial mechanical failure (like the diff) it would do it at all times though, no? Not just explicitly in reverse an when its hot. You say the diff vent tube is dirty, do you think this is the culprit for my symptoms??

 

[I_LIKE_TURTLEZ]

If it was a substantial mechanical failure (like the diff) it would do it at all times though, no? Not just explicitly in reverse an when its hot. You say the diff vent tube is dirty, do you think this is the culprit for my symptoms??

Not necessarily, bearings often only make noise under certain load until they're on the brink of complete failure. I would assume the vent tube being at least partially clogged is what caused a relatively sudden leak, it's normal for the rear pumpkin to seep over time as pressures increase and decrease, the vent keeps the seal from bursting.

Someone is going to have to go under the vehicle and start physically touching and prying on things to find out what's loose. It might not even be the rear end itself but initially that's what it sounds like, it doesn't take long with low oil for them to be cooked, especially the wheel bearings.

 

[seanpmoney]

Not necessarily, bearings often only make noise under certain load until they're on the brink of complete failure. I would assume the vent tube being at least partially clogged is what caused a relatively sudden leak, it's normal for the rear pumpkin to seep over time as pressures increase and decrease, the vent keeps the seal from bursting.

Someone is going to have to go under the vehicle and start physically touching and prying on things to find out what's loose. It might not even be the rear end itself but initially that's what it sounds like, it doesn't take long with low oil for them to be cooked, especially the wheel bearings.

I don't think it was a sudden leak, from the residue on the bottom of the diff it looks like it was seeping for awhile. A new seal totally rectified that issue. The fact that the seal was leaking only became prevalent to me after i increased the size of the rear tires which likely exacerbated my problems creating all that noise initially. After refilling and resealing it went away for a few months now all of a sudden it only happens in reverse during specific circumstances. My best guesses at the moment are the control arms, but i agree; ill need to get it up in the air and pry around to check for any looseness. Maybe do another fluid change if i find out the vent is clogged?

 

[95opal]

I would be looking at the upper control arm bushings on the axle side. If the car has original arms i would just upgade especially since you dont have quads currently.

 

[I_LIKE_TURTLEZ]

I don't think it was a sudden leak, from the residue on the bottom of the diff it looks like it was seeping for awhile. A new seal totally rectified that issue. The fact that the seal was leaking only became prevalent to me after i increased the size of the rear tires which likely exacerbated my problems creating all that noise initially. After refilling and resealing it went away for a few months now all of a sudden it only happens in reverse during specific circumstances. My best guesses at the moment are the control arms, but i agree; ill need to get it up in the air and pry around to check for any looseness. Maybe do another fluid change if i find out the vent is clogged?

Hopefully all it is are worn bushings, fingers crossed for you. If it's filled up with oil right now and sealed, it's fine to leave it.

4.10's with a blower is a pretty wild setup, I already know those tires just get blown off, even drag radials will on concrete. Puts a lot of strain on the rear.

 

[cobrajeff96]

Any sort of awful noise from the rear while turning is likely due to the spider gears being overly worn or those side shims and/or carrier bearings finally wearing out. Probably just change out the whole diff setup really if you're already going to be in there fixing things.

 

[Terrorist 5.0]

Look at the bright side.

At least if your rear end is toast (fingers crossed it’s not), you can get that 4.10 ring and pinion out and put something proper like a 3.55 in.

4.10 with any sort of power adder makes no sense on the street. Even on the strip you should be having traction problems.

I like my gears longer though, just my .02$

 

[seanpmoney]

Any sort of awful noise from the rear while turning is likely due to the spider gears being overly worn or those side shims and/or carrier bearings finally wearing out. Probably just change out the whole diff setup really if you're already going to be in there fixing things.

Well then, could you elaborate on why this stimulus only seems to be present when the car has been driven around for a significant amount of time and mainly only in reverse? I would think if it were a mechanical failure like you're insinuating, it would happen at all times rather then being temperature and direction dependent.

 

[cobrajeff96]

Spider gears don't care whether or not you're driving in forward or reverse directions. It's when the rear wheels are being subjected to different rates of spin that the spider gears truly activate. This is the only time the differential activates (it's right in the name).