When to Change Gear Oil after Rebuilt? - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 21 (permalink) Old Feb 16th, 17, 3:46 PM Thread Starter
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When to Change Gear Oil after Rebuilt?

I changed the gears my 12 bolt last spring. I also put in new pinion, carrier, and axel bearings. I also re-shimed my posi clutch plates according to Tom's Differential video. When should I change the gear oil. I have driven it about 750 miles since the gear change. Thanks
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post #2 of 21 (permalink) Old Feb 16th, 17, 6:39 PM
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Re: When to Change Gear Oil after Rebuilt?

If I was going to change the oil I'd do it now. I usually don't change the oil after a rebuild. I put a magnet inside the rear end to catch metal in the oil.
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post #3 of 21 (permalink) Old Feb 17th, 17, 2:00 AM
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Re: When to Change Gear Oil after Rebuilt?

The next time you change gears is soon enough.
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post #4 of 21 (permalink) Old Feb 17th, 17, 8:57 AM Thread Starter
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Re: When to Change Gear Oil after Rebuilt?

Quote:
Originally Posted by big gear head View Post
If I was going to change the oil I'd do it now. I usually don't change the oil after a rebuild. I put a magnet inside the rear end to catch metal in the oil.
Is there a special kind of magnet? If so where do you get them?
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post #5 of 21 (permalink) Old Feb 17th, 17, 9:20 AM
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Re: When to Change Gear Oil after Rebuilt?

I get 1 inch round craft magnets from Lowe's and glue them to the inside of the cover with 2 part epoxy. I put them at the lower edge of the cover on the opposite side from the ring gear. GM also puts magnets on the inside of the cover on the 7.5 and 8.5 rear ends equipped with limited slip differentials.
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post #6 of 21 (permalink) Old Feb 17th, 17, 10:55 AM
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Re: When to Change Gear Oil after Rebuilt?

I have had several rear ends rebuilt and I have never changed the oil. The rear end shops never said it needs changing. Never heard of anyone changing it for the sake of changing it.
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post #7 of 21 (permalink) Old Feb 17th, 17, 11:54 AM Thread Starter
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Re: When to Change Gear Oil after Rebuilt?

These are kind of expensive with shipping; but look like they would be good.
K&J Magnetics: DC2-N52
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post #8 of 21 (permalink) Old Feb 17th, 17, 1:10 PM
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Re: When to Change Gear Oil after Rebuilt?

This is the instructions given to me when my differential was rebuilt. To keep the warranty in effect I will follow them, a few quarts of oil and a bottle of additive are not very expensive.


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post #9 of 21 (permalink) Old Feb 17th, 17, 8:46 PM
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When to Change Gear Oil after Rebuilt?

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.

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post #10 of 21 (permalink) Old Feb 17th, 17, 9:54 PM
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Re: When to Change Gear Oil after Rebuilt?

Magnets here ya go.

https://www.menards.com/main/tools-h...tegory=magnets

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post #11 of 21 (permalink) Old Feb 17th, 17, 9:54 PM
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Re: When to Change Gear Oil after Rebuilt?

While I would agree on a sensible break-in period on new gears, who here has actually changed differential fluids on their everyday vehicles? Companies who manufacture components have skin in the game and of course will recommend a maintenance schedule, but here in the real world we know these rarely get followed. We also know that failure to follow certain recommendations have a minimal effect on operation in many cases...I point to the millions of vehicles operating on the road today with mileage in excess of 100,000 without any gear failures and without any maintenance. I suspect most here have one of these vehicles...I know my 2004 Silverado w/109,000 miles is one. A properly set-up ring/pinion is a pretty rugged and long lived component as long as there is a proper level of fluid...even without maintenance.

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post #12 of 21 (permalink) Old Feb 17th, 17, 11:44 PM
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Re: When to Change Gear Oil after Rebuilt?

How do you know that the differentials are not broke in prior to installation in a new vehicle? Same with engines, when flat tappet cams were all there were in production there had to be a break in procedure run on them. My ZZ4 crate engine had been run in somehow, cannot remember exactly what the paper said.
A few quarts of oil is cheap peace of mind. I'll break mine in slowly, didn't do it with the Nova rear end and it was always noisy, will not make that mistake again.

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post #13 of 21 (permalink) Old Feb 17th, 17, 11:55 PM
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Re: When to Change Gear Oil after Rebuilt?

More likely abrupt abuse initially or it was not correctly set-up rather than a lack of change of fluid.

Rich

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post #14 of 21 (permalink) Old Feb 17th, 17, 11:58 PM
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Re: When to Change Gear Oil after Rebuilt?

It was set up correctly, big gear head built it. I backed the car out of the garage after 5 years of building and hammered on it from day one. A little older and wiser now.
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post #15 of 21 (permalink) Old Feb 19th, 17, 2:14 AM
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Re: When to Change Gear Oil after Rebuilt?

anybody think race car rears get all this break-in?

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