Differential gear tooth wear pattern?

[Cranky]

IIRC, you broke them in on jack stands? IMO, that's not the way they should be done but since I've never tried that, I really can't say but the destructions that come with a new gear set say to drive the vehicle and do not mention any other way to do it. It's kinda hard to get them to operating temp within a certain amount of time running on stands. I posted a link to the proper way to break in a new set of gears above.

When I got my pinion depth setting tool, it was kinda by accident. A buddy bought it back around 81 or 82 and only used it one time and I helped him that day. It was the first time either one of us set up a rear end. I borrowed it from him around 85 and had it for nearly 10 years and asked again if he wanted to sell it. Felt kinda by now if he didn't have a need for it, why keep it and he finally agreed to sell it to me and I still have it. I've lost count of how many rears I've set up with it and have never had any problems except for one Dana 60. It took several attempts to just get close to the number and ended up being a bit noisy on cruise. May have had trouble hitting the number because I was using some used shims but they didn't look like they were in bad shape.

Usually, if new gears are noisy on coast, the pinion is too deep and noisy on accel is indicative the pinion is too shallow. IIRC, the pinion was .005 too deep but even that figure usually doesn't create a problem and I'd rather be a bit deep than a bit shallow. The gears were Richmonds and the noise was only a faint hum and not a howl and you had to listen for it. If the stereo was on low volume, you didn't hear them at all and it never got any louder over the course of several years. Odd thing was that when I checked the pattern on these, it looked good.

 

[moper]

First gears I did was back around 1992. Did a few here and there for some years, then as a fill in, worked at a 4x4 custom shop. Break in was always the same: On a lift or stands, run it up between 30 and 50 mph for 15 minutes. Let it cool completely (overnight is best). Drive it "lightly" for 5-10 miles with light throttle accel and decel Let cool completely (overnight) before you get on it hard. I have, in a pinch, only done the jack stands break in with a cool down of a few hours. But that was a race situation and couldn't be avoided.
If it was going to make noise you'd hear it on the lift. If you didn't address the cause before the test drive, it would be permanent.

 

[AR67GTX]

What would be improper break-in? Don't recall any particular differential break in procedures for new cars. I ran it at idle for about 25 minutes on jack stands and then took it on 3 each 5 - 10 mile drives at moderate speeds without any heavy throttle use.

 

[Cranky]

What would be improper break-in? Don't recall any particular differential break in procedures for new cars. I ran it at idle for about 25 minutes on jack stands and then took it on 3 each 5 - 10 mile drives at moderate speeds without any heavy throttle use.

Well, moper says that's the way they do it....and on the 3 new vehicles I've bought in my life time, I just drove them easy for the first couple hundred miles. On one, it was at the track making passes with barely 200 miles on it but if you read the owner's manual, it'll give you proper break in procedures for the vehicle and I'm sure it takes the rear end into consideration too.

 

[AR67GTX]

I've had trouble getting together with my mechanic on the differential noise - we discussed meeting next Monday. But I experimented with it some more while running on jackstands. At first I didn't think I could hear any noise but when I sat inside and shut the door and rolled up all the windows I could plainly hear the rumble/howl noise when running in drive at above idle speed. Using a piece of heater hose to isolate noise it definitely sounds like it's from the differential unit. I could pick it up out towards the wheel bearings but it was not nearly as loud. I also tried the hose on the transmission and it transmits the noise from the engine valvetrain - but more like a loud sewing machine. So - pretty sure it's the differential - just not sure if it's the gears or one of the replacement bearings is bad?