clunking noise in reverse and 1st/2nd at low speeds...

paradigm · Apr 10, 2011

Hey all,
So I picked up the mustang today, and overall I am very happy with it. However after some time on the highway, I am hearing a clunking/knocking coming from the middle or rear end, underneath the car, with the clutch engaged whiles slowly going in reverse, or going forward slowly, and ususally whiles turning.

I should mention that the car has some mods, such as aftermarket exhaust, eibach prokit and I believe a FRPP stage 2 clutch. The car in question is a 2000 GT 5-speed which hasn't been driven for the last 4 years, and only has 70k KM (43k Miles).

I also noticed something (that may be unrelated) - basically when in neutral at a stop, or even at a slight incline, the car doesn't roll backwards. It's as if there is some sort of additional friction (stuck caliper maybe?) that is holding the car from rolling freely. In every other manual car I have driven, they have rolled with gravity from a stop, when in neutral with no brake engaged. Do these 99-04 GT's ususally roll freely, or does it take a lot to get them rolling?

trinity_gt · Apr 10, 2011

Clicking or clunking or a chattering sensation from the rear of the car while turning can point to a limited slip issue.

If the car has the original Traction Lok LSD it may simply need an oil change along with a bottle of friction modifier. If the problem persists you're probably looking at a TL rebuild.

You should also verify that the U-joints are in good condition.

Definitely check for a dragging brake. Drive the around a parking lot for a minute or two and coast to a stop (don't use the brakes.) Get out and try to get a sense of the heat at each wheel hub. Be careful if you choose to touch the hub because if the brake is hot the hub will be hot. You can also jack the car up and try to spin each wheel to check for drag. With the LSD you'll want to jack up both sides and leave the trans in neutral.

02red4point6 · Apr 10, 2011

how do you change the oil in the rear end?

trinity_gt · Apr 10, 2011

02red4point6 said:
how do you change the oil in the rear end?

To get the old fluid out you can either vacuum the fluid out of the fill hole using a tube or unbolt the cover, prise the bottom of it away from the housing and let the fluid drain there. The cover is then removed, the gasket/seal material is removed, a new gasket or silicone is applied and the cover re-installed.

To re-fill, fluid and a bottle of friction modifier is added through the fill-hole on the side of the diff case.

Careful with hypoid fluid: That **** stinks like poo and you're going to smell like it for a while if you get it on you or your clothes. That's one job I don't mind leaving to a trans/axle shop

jaskyland · Apr 14, 2011

paradigm said:
Hey all,
So I picked up the mustang today, and overall I am very happy with it. However after some time on the highway, I am hearing a clunking/knocking coming from the middle or rear end, underneath the car, with the clutch engaged whiles slowly going in reverse, or going forward slowly, and ususally whiles turning.

I should mention that the car has some mods, such as aftermarket exhaust, eibach prokit and I believe a FRPP stage 2 clutch. The car in question is a 2000 GT 5-speed which hasn't been driven for the last 4 years, and only has 70k KM (43k Miles).

I also noticed something (that may be unrelated) - basically when in neutral at a stop, or even at a slight incline, the car doesn't roll backwards. It's as if there is some sort of additional friction (stuck caliper maybe?) that is holding the car from rolling freely. In every other manual car I have driven, they have rolled with gravity from a stop, when in neutral with no brake engaged. Do these 99-04 GT's ususally roll freely, or does it take a lot to get them rolling?

I have the same sound in my 2007 GT 5-speed. It wasn't there until the dealer replaced the separator plate in the trans about 8 mos. after I bought the car new. I have had a valve rattle noise in mine since new and that's why they replaced the separator plate thinking that was it. It's still there when I shift. Ford also replaced the synchronizers in the trans because of binding between 1-2 and 2-3 gears, there was a TSB on this from Ford. I have no mods on my mustang.

nancygrl · Apr 15, 2011

trinity_gt said:
Careful with hypoid fluid: That **** stinks like poo and you're going to smell like it for a while if you get it on you or your clothes. That's one job I don't mind leaving to a trans/axle shop

And if you do decide to change it yourself, make sure you do it outside or in a very well ventilated garage, etc... Did mine in the winter, and garage stunk for a couple of weeks.

beater98 · Apr 16, 2011

Also check your rear upper and lower control arms... Mine were shot at 60k and sounded like hell. I replaced mine with Summit Racing after market arms and spring isolators. Made my car drive like new!

clunking noise in reverse and 1st/2nd at low speeds...

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clunking noise in reverse and 1st/2nd at low speeds...

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