I am trying to change my rear differential gear oil on my 1996 Chevy Tahoe 4wd. I was told by someone at Oriley'* that I should use MasterPro 80W-90 Gear Oil and to add 4oz Champion Limited Slip Differential. If I didnt use the additive my rear differential would break. Is this true? I just changed it with the limited slip additive, but have not driven it yet.
Thanks

If it has the limited slip then yes you need the additive. You can tell by the sticker in the glove box. Look for G80 if it has that then your Tahoe has the limited slip rear end.

you absolutely DO NOT want to use limited slip in either rear, there is a gm tsb out on why not to use lim slip fluid in the g80 or open diffs on the trucks. it will mess up the operation of the locker (which is what the g80 trucks have). so you want to use standard non synthetic non limited slip on all half ton trucks and suvs 96-99.

for reference the 2500-3500 use synthetic non lim slip. and i think they changed the recommendation for the redesign in 99-2000, not sure what they have

Please post the TSB article Justin.

LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849).

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

VEHICLES/COMPONENTS INVOLVED: ------------------------- ---- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 10950849 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
© Copyright General Motors Corporation. All Rights Reserved.

That'* good info Justin. It actually applies to my S10 with the G80.

i dont know alot about the small trucks but assuming its a 10bolt with the g80 locker and not the 10bolt car axle with the limited slip diff in it then it would apply to those as well

I just use lucas in mine which it made for either rear end. I have never had a problem using lucas.

Just use Mobil one synthetic 75w90 that'* what we use in our shop. And add the additive if needed.