Breaking in new rear gears

[Bee383]

Picked up my 69 bee today with the new truetrac and Yukon gears.shop owner told me he did the drive and cool off cycle a few times and said not to get it up to high in speed and not get on it for a few hundred miles.he wants to change out the diff oil at about 400 or so miles.anything I should do as well?any tips?had a little whine at about 40 mph.not sure if it would have continued if i had not let up some.thanks four any advice,David.

 

[idrivemopar]

I got a truetrac diff also, and the guy that built mine told me the same thing, just start off with short distances, and gradually work up to longer distances and do not just go run out on the highway until you get up to around 500 miles. Once the gears break in, the whine should go away when you get the pattern on the gears from what i have been told and read on here.

 

[Bee383]

I have about 60 miles on the new gears and the whine that was in the 40-50 mph area is slowly going away.i am just itching to get on it and see what the 3.73 and new truetrac will do

 

[67 coronet]

I have about 60 miles on the new gears and the whine that was in the 40-50 mph area is slowly going away.i am just itching to get on it and see what the 3.73 and new truetrac will do

resist the urge sir!if you want them to last a long time,break them in slowley.all the whine should slowly go away.do just what your builder told you and TAKE YOUR TIME!

 

[tallhair]

resist the urge sir!if you want them to last a long time,break them in slowley.all the whine should slowly go away.do just what your builder told you and TAKE YOUR TIME!

I don't doubt your advice but I am curious why the need for this procedure as I'm sure brand new cars didn't whine back in the day (unless exception) and owners didn't/don't go through this procedure. What is the diff is it the quality of the steel / gears machining steps vs OEM? I got a little insight to gear machining differences when I was looking at gear sets for a Dana 60 that I wound up not buying and read a lot about less machining = less cost and less quality.

 

[67 coronet]

I don't doubt your advice but I am curious why the need for this procedure as I'm sure brand new cars didn't whine back in the day (unless exception) and owners didn't/don't go through this procedure. What is the diff is it the quality of the steel / gears machining steps vs OEM? I got a little insight to gear machining differences when I was looking at gear sets for a Dana 60 that I wound up not buying and read a lot about less machining = less cost and less quality.

most,if not all,builders will set up rear diffs with tighter tolerences and recomend a breakin for that.the oem stuff was set loose to run right off the line.modern gears also figure on a breakin and build there gears acordingly.heat treating of the metals and the procedures they follow are very diff from wnat they did back in the day.with oem stuff it might last 250,000 or only 50,000 miles,you never knew what you got.

 

[Jasoncoronet]

I to have never broke in gears before. I have had about five different rearends and I drive them like I stold them. I believe if the rear end is set up correctly and the proper fluids are installed you should be able to drive it like you want. Also I have had a rearend that has had a wine before and it never went away. This was a setup issue on the gears. After I fixed the mesh the wine was gone. Rearend are tough components thus having no filtering system or cooling. Anybody that has the real truth to this myth enlighten me if you can I would love to know.

 

[Dako]

most,if not all,builders will set up rear diffs with tighter tolerences and recomend a breakin for that.the oem stuff was set loose to run right off the line.modern gears also figure on a breakin and build there gears acordingly.heat treating of the metals and the procedures they follow are very diff from wnat they did back in the day.with oem stuff it might last 250,000 or only 50,000 miles,you never knew what you got.

I can remember several new cars within my family over the years. I'm talking `68, `76, `92, `95, `04. 1st thing?...road trip! One was coast-to-coast! So, at what point (year) did they start doing things differently? Do the auto makers use gears made by somebody that doesn't offer the same product to the open market? That just doesn't make business sense.

 

[Jasoncoronet]

A little info I found out is that each gear Manufacture has there own specs when machining or designing gears. Example would be Richmond there gears tend to be straight cut than others and thus causing more noise but also adding strength. The last set I used were motive 3.55 and they are the most quiet that I have used. I think back in the day the options were not as vast. Gear setup varies to each manufactures. When a builder installs gears it is best to use what he is use to and familiar with.

 

[Cranky]

I too set up gears and do use the recommended specs but....each set of gears that I got had break in procedure. This is from Richmond gear.... http://www.richmondgear.com/01instructions.html
Break In: A new ring and pinion installation, especially a high numeric ratio with new bearings, can cause an excessive heat buildup in the rear end and cause softening of the gear teeth and bearings if a break in is not performed.

Street vehicles should be driven at normal street driving speed for approximately 10 miles, then stop and let cool for 30 minutes. Do this 2 to 3 times. Towing vehicles need approximately 200-300 miles of normal street driving before being used for towing.

On circle track race cars make approximately 6 to 8 laps at slow speed, then let cool for 30 minutes. Make 6 to 8 more laps at slow speed, then 2 to 3 laps at full speed, the let cool again for 30 minutes.

Drag cars need only an initial run-in since they are driven short distances and heat is not normally a problem with proper lube and backlash allowance.

NOTE: If after the above break in is performed, overheating of the rear end is suspected, repeat the final portion of the break in procedures.


I've done a lot of gear set ups over the years and have followed this procedure. Also, if a gear set had a slight whine, it never went away. Even got a new truck once that had a slight whine but it wasn't loud enough to complain about. It went over 100k miles. The failure was the oldest daughter totaling it out....