Last fall, I changed fluids in both diffs and the transfer case. Royal Purple 75w90 in the diffs, GM Autotrak II in the transfer case.
Near the end of winter, I started to notice a faint growl that I thought might be the first sign of a u-joint going. Crawled underneath in the snow, but couldn't locate a problem. A week or two later, 3 hours from home, there was a big "bang" as I accelerated onto the highway, followed by massive vibration. I coasted to the shoulder, reached underneath and found the rear of the driveshaft had a LOT of play. I assumed the u-joint had failed, but gear lube was pooling underneath the diff.
Long story short: the rear diff input bearing grenaded. Chunks damaged gear teeth. $3000 to have the rear diff rebuilt by a drive-line shop. Talking to the mechanic, I noted that there was no sign of excessive wear just a few short months prior. He asked what weight fluid I used, and told me that in his experience this kind of damage can occur when 75w140 is used. Some people figure it must be better because it covers a wider range. Since I used 75W90, I really didn't think too much more about it and just chalked things up to bad luck and high mileage.
A few weeks ago, I started hearing an ominous growl from the front. Crawled underneath, u-joints were fine, play at the input bearing, oil fling line coming from the seal area. Oh oh. I pulled the fill plug and dipped my finger into some very shiny grey goo.
The local wreckers found me a low-mileage replacement in nice shape for a tenth of the price the rear rebuild cost, and I swapped it in (which was an adventure unto itself, but that's a different story...)
Last fall, there was a bit of fuzz stuck to the magnetic drain plug, but the fluid looked OK. So I'm left wondering what could have caused both differentials to fail at the same point in such a short span of time? And the only common factor I can think of is the gear lube.
Comments? Suggestions?
Near the end of winter, I started to notice a faint growl that I thought might be the first sign of a u-joint going. Crawled underneath in the snow, but couldn't locate a problem. A week or two later, 3 hours from home, there was a big "bang" as I accelerated onto the highway, followed by massive vibration. I coasted to the shoulder, reached underneath and found the rear of the driveshaft had a LOT of play. I assumed the u-joint had failed, but gear lube was pooling underneath the diff.
Long story short: the rear diff input bearing grenaded. Chunks damaged gear teeth. $3000 to have the rear diff rebuilt by a drive-line shop. Talking to the mechanic, I noted that there was no sign of excessive wear just a few short months prior. He asked what weight fluid I used, and told me that in his experience this kind of damage can occur when 75w140 is used. Some people figure it must be better because it covers a wider range. Since I used 75W90, I really didn't think too much more about it and just chalked things up to bad luck and high mileage.
A few weeks ago, I started hearing an ominous growl from the front. Crawled underneath, u-joints were fine, play at the input bearing, oil fling line coming from the seal area. Oh oh. I pulled the fill plug and dipped my finger into some very shiny grey goo.
The local wreckers found me a low-mileage replacement in nice shape for a tenth of the price the rear rebuild cost, and I swapped it in (which was an adventure unto itself, but that's a different story...)
Last fall, there was a bit of fuzz stuck to the magnetic drain plug, but the fluid looked OK. So I'm left wondering what could have caused both differentials to fail at the same point in such a short span of time? And the only common factor I can think of is the gear lube.
Comments? Suggestions?