88 Jimmy - Clicking/metal on metal sound. Tranny? Driveline?

[donnyb88]

Hello,

I own an 88 GMC Jimmy 4x4, 350 700R4. Just within the last couple of days Ive been hearing a weird noise from underneath the truck. So far it only seems to happen when I switch from park to reverse, and then for a little while after in drive. But only when I have my foot on the gas. If I just let it idle in reverse and roll it doesnt make the sound, same as in drive itll make the noise only when Im accelerating and if I let off the gas it stops. After a couple minutes of driving it stops completely. Its like a clicking almost metal on metal squealing sound dependent on how fast Im going.

Any ideas on where I can start looking would be great!

Thanks in advanced.

 

[CAVANALK5]

I'm no expert on the matter but my 88 started clicking loud. My rear end is trashed though. Best to have someone drive it so you can listen better at ground level.

 

[hillbilly deluxe]

It might just be a u-joint. Have you tried moving them by hand? I also had a bad wheel bearing that made noise on and off.

 

[donnyb88]

Well on my way home from the parts store (buying new u joints to see if that was the problem) the front u joint slip yoke from the transfer case broke and the driveshaft fell right out onto the road. So I guess that was the problem? Not sure if that was the original problem or if that was caused by something else. And to make things even better my manual locking hubs are worn and I couldnt even get it into 4x4 to get home lol.

Im going to try and track one down and replace it all tomorrow. Thanks for the advice everyone, and Ill keep you posted on whether or not I get her moving again!

 

[hillbilly deluxe]

It's usually just the u-joint. If you're feeling diagnostically inclined you can try to stick the slip yoke back into the t-case, try to turn it by hand, and see if it feels tight or loose or makes weird noises. If it feels or sounds ugly you may have a t-case problem. Oil should have leaked out when the drive shaft fell out if the case was full.

Might as well do both rear u-joints if you've got it out. Also, you may be able to remove your locking hubs and clean/lube them to get them working again if you don't have the money for new ones.

 

[donnyb88]

The part of the slip yoke that holds the u joint snapped right off on one side and let go of the u joint and then the driveshaft. The slip yoke stayed in the transfer case. Im replacing both of them anyways but either way I do need a new slip yoke.

 

[hillbilly deluxe]

Damn, you should put up some pics. I know that when my front axle u-joints have broken in the past the yokes got destroyed too since I was on the throttle.

 

[hillbilly deluxe]

Ever wrench on that thing?

 

[donnyb88]

All fixed

Hey, yes sorry. Ive been having internet issues here havent been able to log on in a while. Its all fixed up, tracked down a slip yoke from an old suburban and put it all back together. Everything worked out.

Thanks for all the help!