New Ring and Pinion Break In Procedure

Discussion in 'Transmission & Driveline Topics' started by Camaro-Chevelle, Sep 8, 2014.

  1. Camaro-Chevelle

    Camaro-Chevelle Veteran Member Lifetime Gold Member

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    New Ring and Pinion Break In Procedure

    Because of the slight roughness of the new gear contact faces and the heavy preloads that must be applied to the new tapered roller bearings, your new rear axle will generate its maximum amount of waste heat in its first few miles. With use, bearing preloads diminish and gear surfaces become smoother. Therefore, the first few hundred miles on a new gear set are the most critical. To prevent premature (and almost immediate) failure of your new gear set, this break-in procedure must be followed:

    All new gear sets require a break in period to prevent damage from overheating the gear oil. The lubrication properties of overloaded or overheated gear oil will be diminished. If the gear oil to breaks down, the end result will be catastrophic damage to the ring and pinion.

    Avoid burn outs, sudden starts and heavy acceleration for the first 500 miles.

    Drive the vehicle gently for 15 – 20 miles, but no longer than 25 - 30 minutes to build up the heat. Do not exceed 50 mph. Let the differential cool down for one hour. Before driving again, feel the differential with the back of your hand. The rear differential should be cool to the touch. Repeat this cycle five times.

    When driving on the highway, vary your speed while avoiding heavy acceleration.

    I cannot overemphasize the importance of changing the gear oil after the first 500 miles. This will remove all metal particles, black phosphoric coating and other contaminants shed by the gears during the break in period. The integrity of the gear oil is compromised as a result. The gear oil must be changed.

    When a posi unit is rebuilt along with a gear change, the clutch discs will break in and settle as well. There will be additional metal particulate in the gear oil from the clutch discs. Again, it is extremely important to change the gear oil after the first 500 miles. I always recommend a good quality petroleum based 80W90 gear oil with GM Limited Slip Additive.
    DO NOT use synthetic lubricants in clutch type limited slip differentials. Synthetic oil makes the clutch discs too slippery. This will not allow the clutch discs to lock up. When the clutch discs slip, one wheel spins. This defeats the purpose of using a Limited Slip differential. Using synthetic gear oil will eventually render the limited slip operation useless.
     
    Last edited: Sep 9, 2014
  2. BeefTip

    BeefTip Veteran Member

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    well, it looks like i broke every rule you just described except for the fluid change lol. I hope i didnt fry something!
     
  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Wow, I was doing burn outs within the first 5 miles after we put new gears in my rear. Could that be why I can hear a slight whine at normal cruise? Honestly, I think I have done everything wrong according to your post. Guess I'll be happy if I can get another 10 years out of this set. :)
     
  4. Camaro-Chevelle

    Camaro-Chevelle Veteran Member Lifetime Gold Member

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    I am always overly cautious. Our cars are huge investments and mistakes are usually costly when a rear differential is involved. If the gears are quiet, you probably didn't hurt anything.

    Corky,
    Is it whining or howling? Those are two different things.
    Gear whine = incorrect gear setup
    Howling (rumble) = Carrier bearings
    High frequncy whine = pinion bearings

    If the whine is only on deceleration and not acceleration, or vice versa, this is an incorrect gear setup. 9 times out of 10 the noisy rearend is caused by incorrect gear setup.
     
    Last edited: Sep 8, 2014
  5. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    It's a slight whine under light load, not decell or acell. I'm not a gear person but I think that usually indicates a loose pinion nut. I've checked it with my torque wrench that goes up to 150 ft lb and it's not loose. I believe I just have a noisy set of gears. IIRC, it's an Zoom set we installed in the 90's with a factory posi unit. I wore it slap out several years ago and we put a Eaton clutch unit in.
     
  6. BeefTip

    BeefTip Veteran Member

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    I actually never knew there was a gear break-in procedure. we have always put them in and go. The only reason the oil was changed in mine is due to a small leak at the bottom of my diff cover. Removed the gasket and used the "right stuff" to make a new gasket and no leak. For what its worth, this was with a new Eaton posi and 3.73 gear install.
     
  7. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Broke all the rules on my new 3:90 setup as well.
     
  8. mgoad1971

    mgoad1971 Veteran Member Lifetime Gold Member

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    Sticky? Good info as I have a new rear end!! Non assembled yet...

    .
     
  9. kimosabi

    kimosabi Veteran Member

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    I vote for sticky!

    I will remember this when I have installed the rear end, Tory. :)
     
  10. FlaJunkie

    FlaJunkie Veteran Member Lifetime Gold Member

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    Great write up! :happy:

    But why did our original factory gears do as well as they did? I didn't follow any of these recommendations, as I am sure not many others did.

    Thoughts?
     

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