I see companies that are rebuilding differentials,many recomment driving the first 50 miles or so to drive very slow,monitor the heat around the 3rd member .Allow the new bearings etc to break themselves in. Is there a recommented grease for newly rebuilt 3rd members or a break in additive ?
we just use the gear oil reccomended by the OEM , but if its new gears the process is more involved . I know some guys put them in and drive 50-100 miles pop the cover and check the gear faces , then change the fluid . just do not get the rear hot, they say to stay under 60 mph too . when I do AAM gears ( GM oe supplier) this is the break in we use AAM Gear Break In Procedure The break in is VERY specific. -Drive 30-35 MPH for 20-30 minutes. -Drive 55-60 MPH for 20-30 minutes. -Come to a complete stop and let the diff cool (15 minutes minimum) This is one cycle. Repeat this cycle 4-5 times. If you don't do this EXACTLY, the diff WILL whine. 500 miles will be needed for a full break in. then change fluid . and wipe out any filings or clean the magnet .
Drive around the block, check for leaks and noises. Then drive down the highway for half an hour, check for leaks and noises. Then mash the skinny pedal and side step the clutch, check for leaks and noises. Change the gear oil in a few hundred miles. This is my procedure and I've never had gear whine or failure.
It's NOT...the bearings..! It's the ring and pinion..! The gear teeth need to be broken in just like piston rings to live a nice long, quiet life. When I put the Quick Change in my Stude, I ran it on jack stands for about 30 minutes (two sessions) in high gear, with the occasional light brake action. I then drove it around town for about 45 minutes (two sessions), with no hard throttle leaving stop signs. I then took it on a round trip of the freeways near me. About a 45 mile trip at moderate speeds with no hard acceleration. I did change the oil after that last trip. From then on, drive is as you will. Mike
While I don't necessarily disagree with the general premise of break-in, I can't help but ask a question or two. How is it that new vehicles, produced by the millions every year, are driven "normally" by most buyers from the moment they take possession and drive axle failures were/are relatively rare? They are assembled from the same parts as are being used in the aftermarket, are they not? If the assembly process is done correctly, i.e., preloads, backlash, etc., why would it be so critical? These questions are being asked to further understanding, not for any other reason. Ray
Hnstray I have often thought the same thing. When I had my 4x4 shop I did a lot of gear changes. Some gear companies had break in recommendations and some didn't. Some gears had a reputation for excessive noise. I would run down the road, come back and pull the cover, check the pattern, check end play, install the cover, new lube and send them on their way.
You are absolutely correct in your thinking. How would one go to the extreme break in procedure with a highly modified race car? As you stated millions of cars come off the assembly line with no instruction for these exotic break in procedures. I think that the recommended procedure is an out for the supplier in case of a failure. We never did that (break in) back in the day.
I agree with Ray and the others. To take it one step further, what about the cars that were fixed under a vehicle warranty for a noisy rear end. I know I fixed my share of noisy rear ends and never followed any "break in" procedure" on a final road test. Can't recall any cars coming back because they weren't "broke in" properly.
the gears when the make them for the OEms they lap them together with a abrasive compound as the finishing process , and ship them oiled and often they are JIT or assembled on site . not shipped non lapped , a little rough and with a protective coating on them ( AAMs which is OE Gm and Rockwells come with some minor mill scale on them from the last heat treat , US gear the gears are clean but still a little rough ) . the break in is the burnishing process . when I used to get semi diffs rebuilt the shop used to have a run in stand to lapp the gears and burnish the faces on them by applying a load to them . and the oil would be real hot and dirty and full of metal you could watch the gears change and polish and hear the electric drive motor change pitch as the gears burnished up and smoothed out . .
Ronnie Sox once told me his break in was back it out of the shop, line it up and hammer the shit out of it.
Yep, my "break in" for anything is to push its limits while my tools are still scattered across the garage floor and my hands are still dirty.
Wow! I'm nearly 70 and retired and just learning I may have don't it all wrong all my Life. I've done an uncountable number of Diff jobs both Race and Street and never done anything but use them as needed. Never had an issue. I've always said I'm more Lucky than Good. The Wizzard
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