GM 14-bolt FF Rear End with 149k miles
Hi to all, Our TV is a GMT400 1997 GMC K2500 7.4L Burb with 149k miles. It is 8-lug, 3.73, GVWR 8,600, with GAWR RR of 6,000 lbs for the full floater rear axle. We believe the rear end also has 149...
Forum Discussion
If the lubricant is SAE grade 75W90 it makes no difference whether or not it is synthetic or not. What is important is the load that the film of fluid can take before there is metal to metal contact.
Seal materials have changed over the years and you want to be sure that the new fluid is compatible with the old seals. Usually GM specifies a new fluid that is backward compatible with older vehicles, but not always. Currently for the rear end that would be the synthetic axle lubricant equivalent to GM PN 89021677 in the USA). With a limited slip rear differential I would stick to the GM fluid and as it is not going to be changed unless something breaks the cost should not be a factor.
Seal materials have changed over the years and you want to be sure that the new fluid is compatible with the old seals. Usually GM specifies a new fluid that is backward compatible with older vehicles, but not always. Currently for the rear end that would be the synthetic axle lubricant equivalent to GM PN 89021677 in the USA). With a limited slip rear differential I would stick to the GM fluid and as it is not going to be changed unless something breaks the cost should not be a factor.
