2nd diff in 2 weeks of towing

can anyone tell me why i might be on my 2nd diff in 2 weeks? i'm towing a 6000 lb travel trailer with my 1999 silverado 2wd 4.8 auto. the truck has an aftermarket tanny cooler too. i was towing the trailer in 3 when the diff started leaking/burning and sounded really bad. took the trailer to a shop in an unkown town, the guy rplaced the gears with non-limited slip gears out of a 2000. he told me to try towing in overdirve and use the tow/haul feature. i towed the trailer another 200km's when it did it again. this time i took the truck to my guy and he put in new gears again non-limited slip...3.73 is the one he put in. according to my gm manual im towing 1000lbs under the max.

anyone have any ideas as to why this keeps happening? im leary to tow this trailer again.

can anyone tell me why i might be on my 2nd diff in 2 weeks? i'm towing a 6000 lb travel trailer with my 1999 silverado 2wd 4.8 auto. the truck has an aftermarket tanny cooler too. i was towing the trailer in 3 when the diff started leaking/burning and sounded really bad. took the trailer to a shop in an unkown town, the guy rplaced the gears with non-limited slip gears out of a 2000. he told me to try towing in overdirve and use the tow/haul feature. i towed the trailer another 200km's when it did it again. this time i took the truck to my guy and he put in new gears again non-limited slip...3.73 is the one he put in. according to my gm manual im towing 1000lbs under the max.

anyone have any ideas as to why this keeps happening? im leary to tow this trailer again.
First off the trans gear and a trans cooler has nothing to do with the rear differential.
Secondly, what was the root cause of the first failure?
It sounds like if the diff started leaking, then maybe the vent was plugged and the diff just build up pressure until the fluid was forced out...no fluid, no lube..differential self destructs
Putting used gears in your diff without properly setting them up could cause problems also installing new gears and not breaking them in first before towing could cause problems and early failure.
Was the correct fluid used?

the root cause the first time was the fluid started leaking out the gears overheated and failed. the new gears i have right now i just got yesterday and have not started towing, how many miles should i wait before i tow again? according to the shop onvoice the fluid they used with the new gears is 80-90w.

the root cause the first time was the fluid started leaking out the gears overheated and failed. the new gears i have right now i just got yesterday and have not started towing, how many miles should i wait before i tow again? according to the shop onvoice the fluid they used with the new gears is 80-90w.
The rule of thumb is 500 miles of driving prior to towing.
During break in, it is recommended that you vary your speeds.

You say the root cause of the first failure was fluid leak...where, how and why did the fliud leak....bad seal?

the root cause the first time was the fluid started leaking out the gears overheated and failed. the new gears i have right now i just got yesterday and have not started towing, how many miles should i wait before i tow again? according to the shop onvoice the fluid they used with the new gears is 80-90w.


Putting used gears in your diff without properly setting them up could cause problems also installing new gears and not breaking them in first before towing could cause problems and early failure.
Was the correct fluid used? I agree with this statement as your reason for the second failure....


the most important thing to remember with the diff is remove the cover and remove the metal debris....also replacing the diff fluid and inspection of gears is needed more often when towing high loads....

if your load is 6000lbs don't forget that the capacity is also including the vehicle with the added load that was added to it also...


with the diff you have now 80-90wt is the oil to use and no additives...i would run vehicle 2000mi open diff inspect gears for proper teeth meshing and debris if it looks good start towing...


make sure the diff vent line is not restricted this can blow out the seals especially towing high loads hot weather as this oil expands alot with heat...make sure the magnet is mounted on the diff cover if missing get new cover with magnet..

DO NOT TOW IN OD.......USE 3RD/TOW MODE ONLY....


next you will need new transmission