My differential whines when the speedo hits 60 mph while cruising along. (Sounds like a semi tire rolling down the highway) At first I thought it was the new tires against the pavement but backing off the throttle at same speed and coasting the whining stops. At any speed less than 60 there is no noise. Burnouts are fine, positraction working as it should. Anybody ever have this happen or any thoughts on what it could be? When the rearend is jacked up and off the ground with trans in neutral everything spins freely. I have replaced all the bearings and seals. Wondering if it's just needing the lash set? The reared does have the W27 cover but that shouldn't make any difference right? Thanks, Ed

 

Noise on gas and decel, none in N or no load usually means pinion bearings

 

X2 or the preload is not set right.

 

If that happened result may be the same, compromised pinion bearings I'm afraid

 

I'm with the others on the pinion bearing.

 

 

Thanks guys, I think you nailed it cause guess what. That's the one bearing I didn't change because I couldn't get the nut off the end of the pinion as I had already removed the carrier first.... Live and learn. But at least that sounds like an easier fix. Appreciate the expertise from everybody. Gives me something to do this week.
One other question. -what is preload?

 

First, to remove the old pinion nut best done with an impact gun. Next step, put away the impact cuz ya can't use it to put it back together. You'll need a new crush collar and one you have changed your pinion bearings you'll install them with a "new" crush collar. Essentially it takes a bit of force to start the crush, some people do use impacts to start it but I'd rather not. Once it starts to crush, it sets the pre-load then you torque it. If you were just changing the pinion seal and not the bearings you'd mark the nut in relationship to the pinion and use red lock tight and re-install in the same location,,,correct way would be check with the axles out how much force with a inch lbs wrench it takes to turn. Some diffs you'll need one to set the pinion as well since they don't have a torque spec but do have an inch lbs setting on drag on the pinion bearings. Kinda long winded but I've seen people mess up diff work all the time

 

+1 on the impact wrench to remove the pinion nut. The pinion rear bearing is pressed on w/ shims to establish one adjustment of the gear mesh pattern (pinion depth; the other adjustment is the carrier bearing side shims for backlash). If you use the same shim stacks w/ new bearings (best starting point), you should be really close on the gear mesh pattern. I'd check that first w/o a crush sleeve so you don't waste a crush sleeve (and the effort of torqueing it). Pinion preload is set by measuring how much torque it takes to rotate the pinion WITHOUT the carrier installed, and then torqueing the pinion nut until you get ~15-20 in-lb of torque to spin the pinion (this doesn't take a whole lot of pinion nut torque when there is no crush sleeve installed, but a whole lot once there is).

Torqueing the pinion nut w/ a crush sleeve installed is the most tedious step of a rear-end rebuild IMO (besides pressing the pinion bearing on/off the pinion to make adjustments). I used an impact wrench very carefully while I used some press-plates clamped around the yoke as an anvil. Hit it 1 or 2 strikes and then check preload. You need to sneak-up on the preload, because if you overshoot it, you need to disassemble and start again w/ a new crush sleeve. If you have a way of holding the yoke w/ a long lever bar, you may be able to manually apply enough torque to the pinion nut to crush the sleeve until you get the proper preload. Good luck.

FYI, bearing preload is the residual force carried by the bearing rollers and races as a result of clamping the bearing/rotating shaft so that there is no slop / play. When there is no crush sleeve installed, this preload force is applied entirely by the torque on the pinion nut, and as a result doesn't result in enough race-clamping force to keep the bearings from shifting under load (but is fine for establishing the gear mesh pattern). This is where the crush sleeve comes in, it sits between the pinion bearing inner races so that it requires ALOT more pinion nut torque to crush the sleeve AND clamp the bearing races to hold them in place under load, and the little extra force above that is carried by the bearing rollers and races as preload.

 

If it's a growling type noise yes pinion bearings,if it's singing type noise on acceleration only then ring and pinion is bad.

 

OK so here's another question. When I changed my differential yoke to accommodate a shorter fatter drive shaft due to an overdrive unit should I have yanked the axles and tried to set the preload again? I'm thinking my pinion is not torqued correctly. Wait-Green Supreme and Oldcutlass you already answered that question and I think the preload should be 15 to 20 inch pounds at this time. Sound like tear down time? I had marked the nut but probably should have used a new nut and taken the carrier out in order to reset the preload correct? Too bad it's 15 cold degrees out there today.

 

I wish you filled in all the blanks in the first post. When you change the pinion, you probably needed to reset your preload with a new crush washer and also when you redid the carrier you need to double check and possibly reset the gear mesh. Wrong preload and/or gear mesh will cause the rear end to sing. Go through the rear end setup procedure and you should be able to get this fixed.

 

With a new yoke, the pinion nut position you marked when disassembling becomes irrelevant. You need to re-establish the pinion preload w/ a new crush sleeve. Too little preload allows the pinion to shift around under load, which causes the various noises. If you've put more than a couple hundred miles on the rear in this condition, I'd replace the pinion bearings too while you are in there.

 

Thanks for the info Johnnyb. I watched this good utube video by Haggerty redoing a 69 Camaro 12 bolt. After watching the video over and over many times I think I can do this job. My yoke wrench came yesterday from Summit and crush sleeve and new pinion nut should come today. I have put about 40 miles of test driving on this car after the restoration. Since I'm using the same pinion, would the recommendation be that I just use the original pinion shim with the new pinion bearings? I have heard that the bearings are made with such close tolerances that going through the process of re-shimming with new shims probably is not necessary. I haven't bought the pinion bearings yet but I do have a 20 ton press in the garage so I'm not worried about changing those bearings. (The Haggerty guy heated the larger bearing in an oven to 450f for 20 minutes and slid it onto the pinion-pretty slick).

 

If you are using old gears, yes, you should use the same shim's, both pinion and carrier. In my opinion changing contact pattern on used gears does not work out. Maybe even go to the extent of checking contact before and after new bearings and compairing

 

I'd agree that bearing tolerances are pretty tight, so changing just the bearings should not require a change in shim stacks to maintain a good gear mesh.

When I installed a new set of Richmond gears in my O-axle, I was able to hit the correct pinion shim stack on the first try based on very careful measurements of the pinion depth WRT the manufacture's spec (it was marked/engraved on the pinion face).

 

Well I got in there on Tuesday and took her all apart. Noticed a shim at the end of the old sleeve and how stout the old sleeve was but didn't think anything of it. Replaced the sleeve and torqued her up. Was there at 15 inch pounds and decided to go another inch and blew it. 70inch pounds. When I got online to order another sleeve I noticed the old sleeve looked identical to the crush sleeve eliminator kit Rock Auto has on their site. So I'm gonna replace the pinion bearings and reuse the eliminator sleeve and shim I removed and torque it to between 6 to 8 inch pounds as recommended by the manufacturer of the kit for the second use. I'll post if the noise has stopped when I'm done.

 

Thanks everybody for the tech help! Problem solved and listening to the nice sound of the engine now on the highway.