strange sound on 98Jimmy

I'd really appreciate if someone can give me any advice on the strange grinding/rattling sound I'm getting on my 98 Jimmy, 118000kms/auto trans. This grinding/rattling sound occurs when I'm driving and the transmission
shift from 2nd to 3rd. It also can be heard but not as loud as I'm gently pressing the gas pedal while doing around 60-70km/h. If I gently drive off and slowly speed up there is no noise as the transmission shifts up. Does anyone have any ideas?
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Is it a 4x4? Could be the transfer case chain getting very loose.
Brian
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Yes, the Jimmy is 4x4 but it does this noise in 2wd. Also noise occurs when accelerating fast and tranny shifts from 2nd to 3rd then after noise goes away. Sam

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Sam wrote:

You may have what was a common occurrence with these transfer cases. The snap ring on the rear output shaft would break, which allows the entire output shaft and internal components to move enough that the drivetrain in the t/case jumps out of engagement momentarily. Usually happened when you put a good load on it (like accelerating).
That's one thing I would check out. If you catch it early, you can simply install a new snap ring and away you go. If you keep driving it while it makes that noise, you are simply destroying components in the t/case.
Ian
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Thanks for your advice! just wondering if I would be able to check for this broken snap-ring.......where do I look? Does the transfer case need to be opened up? thanks Sam

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Sam wrote:

You would remove the rear driveshaft, remove the four bolts that hold the rear extension housing on, and you should see the snap ring, or where it's supposed to be. It sits in a groove on the output shaft on the rear side of the big roller bearing that supports the output shaft.
Ian
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