Differential Questions

[cccccc]

yeah i was wonderin whens the best time to do a overhaul on your rear end? are there any symptons our cars show? how can you tell if the posi needs to be replaced? and are there any noises that the rear makes that would tell you somethings wrong in there? also if my car was in the air and in neutral if i spin the tires manually by hand shouldn't both tires spin in the same direction? if they dont does that mean your posi is bad. i also have bad u-joints in my driveshaft and have ordered the aluminum shaft.

[svobud]

one tire will spin the opposite direction ... yes. that doesn't mean your carrier needs to be rebuilt. normally, you'll hear a whine, growl, or howl when a rear is on it's last leg. you do need to periodically change your diff fluid (be sure to always use friction modifier when you do).

FMS alum driveshaft comes with new u-joints already installed.

[cccccc]

is that when your one wheel constantly spins in that same direction? what if it does it sometimes and sometimes it both wheels spin in the same direction? because ever since my u-joints went bad there has been more and more play in my driveshaft(i can turn the shaft about half way and the tires wont move then when i get past half the gears catch and spin the tires) before the ujoints went bad if i spun the tires in neutral both would spin posi but if i does it now the wheels spin posi till i get past the play in the shaft then sometimes it will one leg and sometimes it will go posi? also my rear end seal is leaking a lil and i dont know how much oil there is in there and when it was changed.

[svobud]

well .. maybe you should think about changing your rear diff oil, ... and inspect everything while you're in there.

[Pat_in_L.A.]

If you can move the pinion yoke up and down at all or move it in and out, then you likely need further repairs other than just the limited slip, because the bearing spacer has collapsed. No use adding diff oil without replacing the leaky seal anyways.

[Ken Potter]

Deposits in gear lube

One other thing to check is when you replace the lube / additive there is a depression / well in the very bottom of the rear end housing. Before you remove the cover try to give your car a day or so to sit without turning the tires. Remove the cover and let the lube drain out until it stops dripping ( may take awhile ). Get a clean white rag and wrap it around your finger. Stick you finger down into the bottom of the depression and rub / move it around alittle. If there are any metal shavings they'll stick to the rag. This is obviously a bad thing. There will be some grey residue from normal wear but the larger the debris the worse condition your rear is in so use your best judgement. To check pinion / ring gear alignment : First buy a small jar of Testors enamel model paint in red, green, yellow or some other bright color. Use a strong degreaser and wipe clean 3 or 4 of the teeth on your ring gear. Brush a thin coat of the paint on the face of the ring gear teeth and allow it to dry completely. Come back and turn your tire in a forward rotation for a few turns. The pinion gear will rub off the paint at point of contact. It should show a small oval patch in about the middle of the face of the gear tooth. Granted this is probably easier with the rear out of the car but can still be done with it under the car. Just some ramblings ...

[cccccc]

Ring & pinion gears???

when do you know if your ring or pinion gears are going out? i think mines is. i changed the driveshaft to find out that my problem wasn't even my u-joints its in my diff. when i spun the wheels they would turn freely a couple revolutions then there would be a loud grinding noise sort of like a clunk, after i turn the tires and get past the clunk the tire would get pretty stiff and it will one leg a little bit then both tires will spin...sometimes, to me i think its my ring and pinion can anybody point me in the right direction from experience from rear end problems?

[Pat_in_L.A.]

Two choices here...

1. Remove diff cover. Clean out all the grease. Identify the source of the "rough" spot and replace the item (this may take special tools and an experienced drivetrain mechanic). Replace the clutches, friction discs, side gears and spider gears in the differential case while you're at it.

2. Find a complete used rear end assembly that will fit in your car from a local wrecking yard for $100-$150 and just replace the whole thing while you rebuild your original as a hobby in your spare time. One popular upgrade is to install an 8.8 out of a T-Bird. The SVO 5-bolt axle shafts fit right in.