differential experts help me decide
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
differential experts help me decide
A few weeks ago, after a Sunday drive, I slowed down for a red light and heard a clanging sound . When I pulled out, I heard the same sound for a few feet, then it stopped and hasn't returned. It resembled the sound when you bang on the drive shaft with a wrench, a hollow ringing sound. I disconnected the half shafts and spun the wheels looking for any binding. Everything seemed smooth, u joints are good , brakes are good, yokes had about 1/8 in. of end play. So I turned my attention to the differential. When I drained the lube in the oil, I found a few fine particles. Some were black and soft, I assume was friction material , and some metal pieces one seemed to look like a tooth chip. I took a small tube and used a shop towel as a filter, and my shop vac to try to vac. any remaining pieces out of the case but didn't get any more. So I refilled it with oil. It took 8 oz shy of 2 quarts on refill. Does it hold 2 qts. exactly or do I have 8 oz. of yuck still in there? Now the hard part, should I run it or pull the diff. for a closer look. My head says pull it, but my back says run it and see if it gets any worse. Removal is a big deal when you have to work on a creeper on jack stands. As always, I appreciate any and all responses.
Thanks
Thanks
Le Mans Master
Joined: Apr 2015
Posts: 9,433
Likes: 124
A few weeks ago, after a Sunday drive, I slowed down for a red light and heard a clanging sound . When I pulled out, I heard the same sound for a few feet, then it stopped and hasn't returned. It resembled the sound when you bang on the drive shaft with a wrench, a hollow ringing sound. I disconnected the half shafts and spun the wheels looking for any binding. Everything seemed smooth, u joints are good , brakes are good, yokes had about 1/8 in. of end play. So I turned my attention to the differential. When I drained the lube in the oil, I found a few fine particles. Some were black and soft, I assume was friction material , and some metal pieces one seemed to look like a tooth chip. I took a small tube and used a shop towel as a filter, and my shop vac to try to vac. any remaining pieces out of the case but didn't get any more. So I refilled it with oil. It took 8 oz shy of 2 quarts on refill. Does it hold 2 qts. exactly or do I have 8 oz. of yuck still in there? Now the hard part, should I run it or pull the diff. for a closer look. My head says pull it, but my back says run it and see if it gets any worse. Removal is a big deal when you have to work on a creeper on jack stands. As always, I appreciate any and all responses.
Thanks
Thanks
Race Director
Joined: Oct 2000
Posts: 12,683
Likes: 3,137
From: Shamong, NJ
You need to use the GM limited slip (or posi) additive, to keep the rear end quite. If your sure you cleaned the rear out sufficiently, ad the posi fluid and then find an empty parking lot, and do a number of figure eights and maybe a few clockwise and counter clockwise donuts.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Sounds like a good way to get arrested for a DUI. The factory never did any figure 8's and neither did the dealers so why do you feel its necessary? The need for figure 8's is an old myth that got started by ignorant fools.
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
Thanks guys i was going straight when the noise appeared. Does the rear hold exactly 2 quarts if so i have 8 oz of crap left in there. I'm afraid a tooth chip got between the ring and pinion . What you think?
Burning Brakes
Joined: Mar 2006
Posts: 829
Likes: 131
From: Spartanburg SC
Mine takes approx 1 1/2 qt plus 8 oz of LS. Some only use 4 oz. I don't believe you have 8 oz of gunk in there. You never said you put the LS in or not. You really should do that and take it for a test drive.
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Le Mans Master
Joined: Apr 2015
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Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
I was testing my transmission a while back and the requirement was to stand on the brakes and put the foot down on the accelerator to see if the transmission clutches were okay. Well the transmission held up but the diff made a funny noise the next time I drove the car. A few figure eights in a local car park and all was well again. I guess the posi clutches didn't appreciate the abuse from the test.
Pro
Joined: Mar 2015
Posts: 681
Likes: 31
From: Nebraska
That's interesting because I just read a couple service manuals that say to do just that.
Last edited by COOLTED; Nov 2, 2015 at 03:05 PM.
Race Director
Joined: May 2006
Posts: 18,740
Likes: 2,583
many years ago I did time trials and autocross. Heard a noise from the rear changed the fluid and added the additive. Ended up blowing the rear on the Long Island Expressway at speed. The ring bolts loosen, eventually one or more may fall out or have the head shear off.
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
ouch what did that cost? I was hoping for some wisdom from tracdog2 or gtr1999. I don't have any super duper motor, but I don't want to get stranded either. or worse bust the case from something getting between the gears.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
No, it won't. I've changed rear end lube in mine at least 4 times in the last 36 years. Used the lube with the LS additive already in it and never needed anything else.
Racer
Joined: Jul 2009
Posts: 338
Likes: 9
From: South Bend IN
NCM Sinkhole Donor
If you really want to see if it is still dirty in there drive it around and really let the new oil get warmed up and mixed in. Then pump and little out so you can see what it looks like. If it looks new, I'd say you got it all out, but if it is dirty I'd say you might need to take it apart.
Le Mans Master
Joined: Apr 2015
Posts: 9,433
Likes: 124
That is a good call on the parking brake. Kind of a pain to check though if the factory rivets are still holding the rotors on.
Le Mans Master
Joined: Apr 2015
Posts: 9,433
Likes: 124
Just trying to be helpful.
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
Thank you all for your responses. I never experienced differential chatter before so i don't know if thats what i heard or not. It hasn't done it since. It was a sound like the drive shaft was banging back and fourth. Like an 18 wheeler when pulling out on a hill. I don't want to do any damage to the case to the extent that it can't be rebuilt. I only have about 75000 miles on the car.