It acts like it pops out of gear but makes no popping out of gear noise. Its a very high pitch WEEEEEEEEEEEE . It only does it coasting down hill with my foot off the gas. If I go down the same hill with the transfer case engaged in 4 wheel drive it does not do it. 1998 2500 350 vortec motor
SOURCE: Front drive, 4 Wheel drive won't engage
Check the switch on the transfercase remove the vacume lines if there is oil in them the switch has to be replaced and the lines should be cleaned out you should also check under the battery tray to make sure the boot is not ripped that controls the leaver to engage the front axel
SOURCE: When my 4 wheel drive
sound like the problem is your vacuum control switch on the transfer case.
SOURCE: Just had motor & transfer case cover replaced
sounds like the universal joints on the rear drive shaft
SOURCE: 1999 GMC Sierra 4WD -
Hi,
The most common problem with this is the clutch packs in the transfer case, they sound like like are not locking up the front diffs properly and may need to be adjusted or replaced.
You need to do a pressure test of the fluid transfer section to ensure that there is the correct pressure to engage the clutch packs then if thats ok start to look at adjusting these.
Let me know if you need more infromation.
Thanks
Jason
SOURCE: GMC '91 Jimmy, Transfer case. When in two wheel
Yeah your right about waer but you might be blaming the wrong part. With the truck up on jack stands ( all wheels off the ground) have a helper drive the truck at the speeds that make the most noise you'll find it in the front axel or fround U joints or drive shaft splines ( drive shaft jumping ) You watch the parts moving and the joints or the cable that shifts the ront axel in and out not moving all the way it uses a vacume motor under the battery that has a cable going to the front axel. the clutches that are in the front axel have clips on them that hold the side gears that engage and disingage as you turn it on and off the clips break get lost fall off were out and let the side gears do as they please and they runinto each other a click and pop/ the cable and the shift fork that move them also fail but not htat much as the cable fails and the vacume leak pulls on a spring in two wheel and it may not be pulling hard enough/
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when it starts screaming there is no longer any exceleration until I put the truck in neutral. Once the noise stops I can put it back in gear
Having the same problem. 225k miles. Did drop and fill on transmission, nothing broken. Changed transfer case fluid. New case back tells me pump rub has been done. Still get hign pitched whining when coasting off higher speeds in 2wd. Shifts and engages 4wd fine. Any help, much appreciated.
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