How do you know if your rear diff is going south? What kinda symptoms would you get?

 

I could tell my diff was finished by the way it went BANG as I took off from a light. No kidding it blew itself up and put a hole in the casing. What an expensive mess.

That was on my '88 oh yeah it howled for a week before it went BANG.

RP.

 

Well, on the rare occasion, I can hear some noise like it's coming from the rear, but it's hard to distinguish whether it's road/tire noise or something else.

I guess I should try to do a burnout tonight and see how many tracks I leave. That should be one way to tell if the posi's still doing it's job. I've got a slight leak, so I'm gonna be changing the gasket and of course fluid.

 

Maybe you should change the fluid and replace the gasket before doing any more testing. If you've leaked enough fluid already- you may be starving the bearings on the axle shafts and the main caps.

 

Eric is right man. You should change your gasket and fluid and check your diff gears for wear, chips, cracks and your old fluid for any signs of metal deposits. I don't think a burnout is a good diagnostic tool to use, although it is damn fun. Heres hopin its nothin serious man.

 

The fluid should be ok, I just checked it last weekend and it's only a very very minor leak. I'll be changing it soon though.

 

Irocker, I personally have had a rear end break on me...

The sound that comes fisrt is a very faint buzz... not quite sure how to put it.. it was very uneasy sounding, it disappears when accelerating, but left in neutral when cruising not under load it is really loud. Simply put one day while launching hard I heard a loud bang... then I knew full well where it came from. It was wickedly louder buzz is all I can say then what happened next really did it, it broke on me and all you could hear was a CLANG CLANG CLANG like one of those forging moulds banging on hot iron... I will never forget the sound and if I heard it on yours I would probably recognize instantly if its gears or not.

If the posi is going, you will hear a noise as well, but that from the differential not locking, what happens next is you will find it works just like an open end and you'll get 1 wheel peel. It may be rebuildable, it may not be depends on the condition its in...

Good luck and I hope its not gears...

 

IROCKER

I have had 2 10 bolts go on me, 1st was a 7.5 inch(S10 Blazer) and the most recent was a 8.5 inch. They both had the same symptoms described in the above posts.
A slight leak at the inspection cover is not a huge concern, however a pinion seal leak should be a red flag. If your pinion seal is leaking then I recomend removing the driveshaft from the rear end yoke. Then you should check the yoke for any play, side to side and up and down, there should be NONE!
If there is, install a new seal and retorque using a NEW pinion saft nut, go with the bearing preload spec in the manual. The nut may only be used once. Watch it carefully, if it become lose again remove the inspection cover to see if the pinion gear was so lose that it came in contact with the carrier assembly( that is was happen to my 85 K10 truck ) If it did....rebuid time

Bill

 

Well, it seems like it's making a bit of a noise. It's very faint, and hard to describe. I'll change the fluid in a couple weeks and hope that fixes it. I still haven't decided whether I want to use synthetic again or go back to the dino oil. Hmmmm...

 

I have had a couple of rearends go south on me.

The first one was in a chevelle I had that I was racing. it would clunk when you put it in gear. I checked all the u joints but there was no problem there. When you had it jacked up and turned the tires there was about a quarter of a turn of backlash in the gears. The clunk indicated that the ring and pinion gears were worn because when it finally went completely and I took it apart there were basically no teeth left on the ring an pinion.

The second rearend went at about 120kmph on highway 11 north of Gravenhurst. This time it was in my Camaro and for about a day prior to it going i could hear a hum coming from the rearend. Kinda sounded like bad road noise but a little louder.
This was resulted in a big BANG and the car doing a 360 on the Road. When I got it to the garage and took off the inspection plate found that the front pinion gear bearing had fallen apart and allowed the pinion to fall down and jam the ring gear against the pinion and housing. Root cause was likely lack of oil as removal of the inspection plate revealed the rear end was bone dry.

Although your noise doesn't sound like a lack of oil it does sond like one of the pinion bearings is about to go south. I would take it apart and check all four bearings. the two on the pinion and the two at the side of the carrier.

They should rotate smooooooothly with no clicking or sticky spots.

 

Ratchet: How do I check the bearings? Unfortunately I'm not gonna have time to do the fluid change for a couple weeks, but the car won't be moving too much in that time anyway, so no harm. I gotta help my buddy do his rad, that's my first priority. And I gotta fit in doing a spark plug change too.

 

Check the ring/pinion gears first... they are usually what breaks from repeated launches... I busted my stock 2.73 gears with a dying TBI... imagine what your 350/TPI combo in good shape would do to your stock gears...

Smae symptoms.. an initial hummm at speed/load... only getting progressively louder as time and beatings go on... soon enough it just breaks. I suggest one night just go for a very thorough examination of the gears for cracks/odd sounds as you rotate it. If the gears are perfectly aligned and are in good shape, there should be no sound really as you rotate it since the gear teeth are designed to very small tolerances in spacing. If a gear tooth is cracked then its off by a few mm and will make a small impact/stick to its mating gear that you won't miss. At speed this is what you'd be hearing as a hum.

 

Thanks dude. The last time I changed the fluid, about a year and a half ago, everything looked in good shape. I'm hoping this is still the case, but we'll see. The Borg-Warner units are supposed to be much more durable than the regular GM ones.

 

I had the same problem as you and others but I got to it before the loud bang. Tried changing the wheel bearings but that didnt help of course. Changing the ring and pinion bearings and seals fixed the hum and havnt had any problems since, except sometimes I only do a 1 tire burnout, before the rebuild i NEVER did a one tire burn.

 

Sorry for not replying sooner Wifes got me working on the Honey Do list.

To check the bearings you must remove the pig then take the two bearings off the end of it. Next you have to take the pinion gear out.

Removal method if required
( 1 remove driveshaft from rear yoke
(2 loosen nut on front of pinion shaft
(3put rear axle on jackstands
(4 remove tires and brake drums
(5 remove rear cover from differential
(6 remove bolt from side of pin that goes through the center of the carrier
(I REALLY HOPE yours isn't broken. It is very common for these bolts to break about half way up the thread so when you go to take it out all you get is half the bolt and the pin is still locked in position.)
(7 push axles in towards centerline of car
(8 remove c clips if they didn't already fall into the bottom of the differential
(9 pull axles out enough to clear bearings at end of carrier
(10 Remove 4 bolts that hold bearing caps in place
(ll Mark shims at sides of bearings to ensure proper replacement they are different thicknesses.
(12 pull the pig out
(13 remove the pinion shaft

With the Pig and the pinion gear out you can check all 4 bearings. I would leave the big bearing on the pinion gear unless it is damaged.

To check bearings
1. first of all visually inspect them for small shinny slivers of metal or chrome.
2. clean bearings in solvent
3. hold on to inner race and rotate bearing if you feel clicking or tight spots bearings are toast.

 

Dude, thanks for the detailed instructions, but there is no way I'm doing that kinda work without a hoist (which unfortunately I don't have in my garage). If there's not a easy way to check it without removing all that stuff than it's gonna have to go to a shop. And if I pay them to do all that work, I'm just gonna get everything replaced anyway since it's all apart.

Regardless, thanks for the help.

 

If you have a 9 bolt..You can pull the axle without opening the diff cover..Since its a full floater you can just take the bolts off the hub and pull..No c-clips..

Daz

 

That's interesting!

Still not doing it though!