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Posted by David Sherman [24.32.202.83] on Tuesday, November 17, 2009 at 23:29:17 :
In Reply to: Re: Hey David Sherman posted by joseph silva [75.132.246.158] on Tuesday, November 17, 2009 at 22:45:57 :
I don't know about the M37 T-case, but I had an M35 whose transfer case screamed badly and it was due to broken and worn bearings. It's not the bearings themselves that cause the noise, so much as the fact that the shafts slip out of position and cause the gears to mesh badly. It sounds like it's tearing itself up, but I bet if you take it apart now before you drive it much further, the gears will be fine and you'll be able to get by with just replacing bearings. Another problem I had once was I left out a thrust washer which caused one of the gears to rub on the inside of the case.
First make sure the noise really is abnormal. If you don't know these old trucks you might think a normal noise is terrible. Also listen closely and make sure you know which gearbox it's coming from. Once you're sure it's abnormal and it's coming from the transfer case, there's really nothing to do but pull it out and overhaul it. Any further external diagnosis is just going to lead to an overhaul anyway, so you might as well dig into it. You can check the shafts for wobbling, check the oil for metal powder, try to listen closer to localize the noise, a and so on, but no matter what you find, you'll have to pull the unit from the truck and tear it apart, so why bother? Once in there, look at every bearing and replace any with visible pits. All should be available from a good bearing house, as should the seals. A slight dullness on the polished surfaces is okay, but anything that can snag a fingernail or that looks like a distinct pit or scratch is cause for replacement. In my case, the broken pieces of rollers that came out when I drained the oil were a pretty good clue.