Not about a Buick per se but differentials are differentials. I had installed a junkyard differential in my Pontiac G8 out of a 2013 Chevy Camaro over the winter. This is direct bolt in type swap that other people have done. The Camaro had supposedly had about 50k when junked. Drives fine but there is noise under certain conditions. Under load, it is quiet but when I coast I hear a road noise or whine. When I make a left or right turn this road noise or whine is especially loud. My car is manual and when shifting into gear it seems that the drivetrain feels like it has a bit more slop in it than it used to. I got a bad feeling that despite the lower miles, it needs some maintenance. Any thoughts as to what could be wrong?
Hey Walter, don’t mean to hijack your thread but I have a Rear End question and I saw Brian was out there. I have a 69 Buick Skylark. Ever since I have owned it, about seven years, It has a very slight whine when there is a load on it. If I let off the gas even the smallest amount the whine goes away. Doesn’t make noise any other time. I have put thousands of miles on it, mostly highway, and it is definitely not getting any worse. Can this be adjusted? Or does it depend on how much where the ring and pinion have incurred? I want to buy a Positrac unit for it. Can it be adjusted at that time?
Check the pinion nut... Also disconnect the drive shaft and push the yoke up and down and try to pull it in and out...IF you can move it in the slightest the nut is either backing off or the pinion bearings are already shot. REMEMBER you pulled a rear from a 50K car that was totalled...YOU KNOW WHY it got totalled??? Likely they ran the car hard and smashed intro something... Jim
Thanks for giving me a few things to check before diving in Jim. Yea, I'm aware junkyard parts can be a roll of the dice. I saw a picture of the car the unit came out of and it was front end damage. On the other hand it was a Camaro with stick, so very possible it had a rough life.
SQUARE head on damage is terrible for the drive line. It pushes the engine back trans back and driveshaft right into the rear end. I have seen housings on solid axles crack from a head on collision ... Hoping for the best for you. Jim
I got some time to work on the car. The pinion nut seems fine. The yoke feels tight as far as I can tell. I pulled the cover off to take a look inside. Nothing jumped out as being messed up. Everything turns smoothly. All the teeth are in good condition. I couldn't really get a good look at the spider gears. Though what little I cood see looked OK. I finally decided to put a dial indicator on a ring tooth. Turning the yoke by hand with the rear wheels locked, I get a solid 0.040" of play on the dial indicator. I don't know what the spec is supposed to be but that seems like a lot.
THAT is way too much - You really should be holding the yoke solid and rock the ring back and forth to get the backlash reading. Try again this way and if you get .040 then that is the problem. You either have a carrier bearing going away or the ring and pinion are wearing away. Pics would be nice of the parts your looking at.
I did go back and redo it the way you say - hold the yoke and move the ring. Got a solid 0.020 - 0.030" movement. I'm coming around to that the pinion bearing may be damaged. I'll try and post some pics.
Well if pinion bearing was damaged ...the pinion would move up and down or in and out. MORE likely the carrier bearing are worn or someone was in the rear at one time or another and swap the left and right carrier bearing shims to the wrong sides and that is what will give you a huge wide backlash... We see that alot.
Hypothetically speaking if I were to swap them, would that fix the issue? Obviously I would check the contact pattern before I declare things 'fixed'.
Pinion bearings will growl, starting at a low road speed then increase the faster you go, it will be pretty constant.
I don’t know if your differential has ever been messed with but if there is no leakage from the seal and the pinion preload is still properly set then look to the carrier because, well, that’s a lot of backlash. Remove the axle shafts and if there is no leakage or noisy axle bearings there, yay, move on to the carrier. The backlash would optimally be in the .008 to .010 range. Now again I have no idea if anyone has been into your diff. before but... providing the main caps are still in their factory position punch mark them side to side top/ bottom. Remove the four bolts and grabbing the ring gear, give it a yank. If it already fell out when you removed the caps or if it easily pops right out then your carrier preload is too loose. Hopefully you have to use a pry bar or two. If not then this can be caused by multiple things. Worn down cast side shims, worn bearings / races, even a bearing that has spun on the carrier and wore itself into the carrier base which is visible only after removing the carrier bearings. Even a previously bad set-up could be the issue. If the carrier surface under the bearings is good and the bearings and races are good then yay! Maybe, just maybe you can swap shims but only if the carrier came out reasonably tight in the first place and if the thicker of the two shims was on the right side of the housing. If not you are going to have to buy adjustable (preferably interlocking) shims and work from there to get your preload and backlash back to within specifications. You need a micrometer and a magnetic base dial indicator. I know it seems like a lot to it but that’s because there is. Driveshafts and differentials specifically have kept me employed for 32 years.
Thanks for the feed back Tim, I appreciate it. I was hoping to avoid completely dissasembling everything until I found a 'smoking gun' but seems like that's not in the cards. I did just check the torque to turn the yoke and I got like 45 in-lbs, which is crazy high. I also checked the contact pattern. I saw something weird but it may be normal. On the drive side of the gear the contact moves between the center and the toe (inside). On the coast side it does the opposite, moving between the center and the heel (outside). Otherwise the contact looks OK.
Finally got some time to do some teardown on this project. Pulled the pumpkin and with a home made case spreader got the differential/ring gear out. Based on my in-experienced eyes, I'm not seeing any signs of an obvious problem. Ring and pinion teeth look OK. Bearing and races look OK. I haven't pulled the pinion out, but it has zero play in it as far as I can tell. The only possible off thing I see is when I look at the contact track on the two races. Seems like in one spot it's perfectly centered. But rotate it 180 and it looks like the track has moved up (larger diameter on cone). Could be normal as far as I know. Decided to check the axle bearings. I removed the brake pads to be sure there was no possible support that could mask any play. Rocked the rotor top to bottom and side to side. Solid as could be, no noticible play felt. I went to rotate the rotor. It would spin fairly freely for 180 and then for the rest of the 360, there is a drag that will stop the spin unless I push a little harder. Both sides do this but passenger side is definately worse. I haven't pulled the pinion yet because the nut on there looks like it will be a real pain to get out. But as I said it feels solid. At this point I'm thinking of putting it all back together unless someone has a suggestion.
no where do i see you give a backlash reading on this gear set?? What is it? 45inch LBS does seem a bit heavy maybe the bearing is taking a crap from a old seal leak? and someone over tightened it? ALL these things are guesses. as not having more info from you and being able to know what the backlash on the ring to pinion is etc. FoR that gear it appears to be a 2 cut gear and traditional book patterns will not look the same as a 5 cut gear ( 2 cut gears have a very small mark where the gear will touch. ) back lash is 1-3 thousands also. 5 cut gear is in the 6-10 thous. So if your backlash is wide on a 2 cut gear your likely going to get that whine pitch noise .. AGAIN... I am just going off what we see in this thread and info we have so far. Jim JD Race
Backlash I measured before dissassembly was 0.020 - 0.030". From my own research I believe I have the GM 8.6 IRS (218mm) rear. 2 cut gear. Torque to turn pinion should be 28 - 42 in-lbs. A spec I found says b/l to be 0.003 - 0.006". So it looks like I did find a smoking gun after all. As you and Tim suggested, seems there is a problem with the shims. I will get some adjustable shims and get that b/l to where it needs to be.
So I rebuilt things to confirm that backlash measurement. I made sure to put the fatter shim on the left. Backlash now reads 0.004". Looks like the shims were swapped and now its good.
Have you driven it to test? Pretty admirable and brave to blow apart a rear, I don't have the guts. Or the right tools.
Not yet, but I hope to get it back on the road before the weekend. It's really not that hard, though you need a verneer and a dial indicator. Transmissions are similar, not as hard as people think but do require some special tools. And you need the correct specifications for both.
