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Hello. From what you describe it sounds more like a differential issue or brake issue. The best way to test is to drive the truck up to speed and then let off the gas and let it coast to a stop and also manually down shift each gear to put more load on the truck. If the issue only happened when the brakes are pressed then the brakes are the issue. Try that and let me know if it helps. I will do my best to help. Lou
Ok I think first you should remove the diff cover and inspect the spider gears and the pinion bearing. Also front diff, maybe just remove the drive shaft. Does it only do it in 4wd?
Ok what about driving up to speed and throwing the truck in neutral and coasting or pressing brake while in neutral ? Have you tried that ?
Ok then it will be rear diff most likely. I would say remove the rear driveshaft and put it in 4wd and do the test again with the rear driveshaft disconnected and see if it does it. Of course this is with it up in the air. I do believe the truck should drive without the driveshaft in 4wd but I don't recommend that I was just saying. So try that on a lift or jack stands.
So far it does sound like a rear diff issue.
Ok fair enough. Just trying to do what I can to assist in diagnosis. Your on the right track it seems since every suggestion I have is something you've done or are on the same page with. So just let me know what you find or if you need any more of my suggestions. Have a good night. Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! 😉 Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou.
Well you can have one fail and not the other. So the things you will need to check is the tooth wear on the ring , and the play in the pinion bearing with the driveshaft detached. And when rotating it should not feel gritty. The best way is to use a dial indicator and check for backlash. If you don't know how to do these I can walk you through it. It's easy. Time consuming but easy. So again you can have ok spider gears and bad ring and pinion , both be bad , or vice versa. If you pull off the rear cover and are not sure then do not take anything apart. We can go to a phone chat and I can walk you through what to look for and how to check each.