Diff fluid change?

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The owners manual for my '02 Suburban calls for checking the fluid levels in the front and rear diffs every 7,500 miles, but never calls for a complete change. I have only owned the vehicle for about 5,000 miles and am not sure if the PO changed the fluid, but doubt it as he pretty much stuck with the specified PM schedule, performed by a local dealer.

Should I change out the fluids, and if so, when?
 
Without records it is a good idea to change all fluids and filters to provide a starting point for future maintenance.
 
I would recommend changing it. If there isnt a drain plug I would use a suction pump to siphon the old fluid out and replace it with new fluid. Check the specs for what it calls for (cant imagine it is anything else but generic 75w-90 Dino) and fill it up.

Regarding if it was changed by the dealer, if the dealer did the correct service work then it would have been changed every 30k. You can check the dealer and obtain their service record for the vehicle. but it is worth it to just change it anyways. At least that way you know it is fresh
 
GM truck differentials require fluid change after the first 500 miles of towing. If you don't tow, every 50,000 miles is OK. You can even go to 100,000. I believe recommended standard gear oil change interval is 30,000 miles.
 
There are about 122,000 miles on it right now. The reason I believe it was not done at the dealer by the PO is that changing the fluid is not called for in the service schedule, only checking the levels and topping off. Also, I do not believe that the diffs have drain holes, again bringing into question the need to do a full change. I believe the schedule calls for changing the transfer case fluid at 100,000 or 150,000 miles, but no mention of changes for the diffs.

And it takes 75w-90 syn for the rear and 80w-90 dino (no mention of syn, anyway) for the front.
 
Last edited:
Originally Posted By: NMBurb02
There are about 122,000 miles on it right now.

I would change the fluids in both axles, transfer case and transmission; unless previously serviced they are all "due".
 
Pull the cover off the differential housing and clean out the crud. I think the reason they spec syn gear oil in the rear is that they made the gear set as small and light duty as they thought they could get away with and need the added protection of the synthetic gear oil.
 
Originally Posted By: 2010_FX4
Originally Posted By: NMBurb02
There are about 122,000 miles on it right now.

I would change the fluids in both axles, transfer case and transmission; unless previously serviced they are all "due".


+1
 
Sounds good. I'll go ahead and do both diffs. Rarely run 4x4 (maybe 5 miles in the last 5,000), so I'll wait until I hit the required service interval (150,000 mile, IIRC). Tranny fluid was done when the transmission pan gasket was replaced shortly after purchase.

Any idea how much fluid each axle will take?
 
Not sure, here is what amsoil says. A lot of it depends on the gears but unless you have the HD model I would just plan on heaving enough for the middle option:

ACITIES:
Engine, with filter..........6 quarts [1]
Cooling System, With Front & Rear AC Initial Fill..........15.9 quarts
AMSOIL Antifreeze and Engine Coolant
Cooling System, With Front AC Initial Fill..........14.4 quarts
AMSOIL Antifreeze and Engine Coolant
Cooling System, Without AC Initial Fill..........14.3 quarts
AMSOIL Antifreeze and Engine Coolant
Automatic Transmission, 4L80-E Initial Fill..........7.7 quarts
Automatic Transmission, 4L60-E Initial Fill..........5 quarts
Automatic Transmission, Total Fill
4 speed 4L80-E..........13.5 quarts
4 speed 4L60-E..........11.2 quarts
Differential, F4WD Front..........3.4 pints
Differential, S4WD Front..........3.4 pints
Differential, 9.25 RingGear Front..........3.6 pints
Differential, 10.5 RingGear Rear..........5.5 pints
Differential, 11.5 RingGear Rear..........7.6 pints
Differential, 8.6 RingGear Rear..........4.9 pints
Differential, 9.5 RingGear Rear..........5.5 pints
Transfer Case, NVG 149..........4.9 pints
Transfer Case, NVG 236/246..........4 pints
Transfer Case, NVG 261/263..........4 pints
 
If your rear axle is the same type as my 02 Silverado it should have a drain plug. If you have the time you can pull the cover and clean out the diff cover magnet and the housing if you want to.
 
Should I take the Burb for a short drive to warm up the diff before draining and cleaning? I plan on doing an OC at the same time and usually let the engine warm up a bit to make the oil flow out a bit better, so I could just drive a few miles to pick up the gear oil and a sixth quart for the OC.
 
If you are just going to use the drain plug, a short drive will help in heating the differential oil for a complete drain. I would recommend pulling the cover and using brake clean to completely remove all residue from the differential.

If your Suburban does not have an anti-swaybar close to the differential cover, you may want to replace the cover. I replaced the differential cover on my father's van with an aftermarket cover from Mag-Hytec. Their covers increase capacity, have cooling fins and have a magnetic dipstick to show any wear on the unit. http://www.mag-hytec.com/
 
After checking the fluid level and color, I decided to wait on a fluid change until I have a little more time and money to do it right.

Those diff covers look pretty nice, but I don't think I'm ready to drop $250 on a replacement cover when the stock one appears to be doing just fine. I don't tow or really load the vehicle down, so I don't have much need for improved cooling or higher capacity.
 
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