GM Drivetrain & Suspension Chassis | Transmission| Driveshaft | Gears/Rear End/Differential | Traction Aids

how many miles to break in a new gear install?

Old May 28, 2005 | 12:09 PM
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Default how many miles to break in a new gear install?

im about to get a posi and 373 installed, but i want to go to the track and see what this bad boy will run. so i was wondering what is a good amount of miles to put on the rear before getting on it pretty hard.
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Old May 28, 2005 | 12:30 PM
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There are going to be many opinions on this. I have always run them through a few heat cycles (4 or 5) with out any serious WOT runs. After that, it was open season.
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Old May 28, 2005 | 12:55 PM
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The rule of thumb is 500 with several heat cycles. I only took easy on my gear for the first 100 miles then I beat on them and no problems so far after 30+k miles.
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Old May 28, 2005 | 02:15 PM
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Yeah, different shops say different things. I did a long single heat cycle at slower speeds, cause I was a ways away from home. Then let cool down completely and did a seperate 20-30 minute heat cycle twice. Then I beat on em. 20,000 miles later still doing good.
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Old May 29, 2005 | 12:21 AM
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I did the same swap w/ Richmond gears and Eaton, took it easy on mine for about.........30 miles. Then sprayed a little happy juice to it. Has been working great for about 5-6k miles w/no problem.
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Old May 29, 2005 | 02:21 AM
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if you set them up right it shouldent be an issue just get a few miles on them bafo you get happy
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Old May 29, 2005 | 11:53 AM
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drive around for about 15 min, stop, cool off, drive another 15 min, enjoy....

recheck backlash at about 200-300 miles
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Old May 29, 2005 | 04:29 PM
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I had strange 4.10's put in and ran about 50 miles on it... then nailed the **** iout of it all night.... and 24000 miles later still no problems...

Just make sure you get the Master Installation kit that comes with the pinion and side bearings....

Good luck with it
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Old May 29, 2005 | 06:57 PM
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It is important with new bearings to get 3-4 heat cycles in them. New bearings generate a lot of heat, so you need to wear those in. At least 15 minutes of run time followed by a long cool down.
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Old May 29, 2005 | 08:17 PM
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also, make sure to change out the fluid after your "break-in" period.
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