Squeak when downshifting.

[83greenbean]

Thanks in advance folks! I have a 1983 k20. This truck recently (as in yesterday) started to make a high pitch chirp when down shifting. It also almost feels like there is slack in my rear end if that makes any sense.

With acceleration I feel nothing, hear nothing. When I downshift and build pressure my truck produces this sound. I've searched the exhaust for any leaks (none found) no slack in the drive shaft or any play whatsoever.
I can not replicate this issue when sitting in the drive way so I'm assuming it's in the rear end but cant make heads or tails of as it's ONLY when downshifting. No chatter, no noise, nothing abnormal under the head. Truck still runs, drives, brakes, and overall has no problems. Just this noise. Any advice on where to look will be greatly appreciated. Thank you!

 

[1987 GMC Jimmy]

Thanks in advance folks! I have a 1983 k20. This truck recently (as in yesterday) started to make a high pitch chirp when down shifting. It also almost feels like there is slack in my rear end if that makes any sense.

With acceleration I feel nothing, hear nothing. When I downshift and build pressure my truck produces this sound. I've searched the exhaust for any leaks (none found) no slack in the drive shaft or any play whatsoever.
I can not replicate this issue when sitting in the drive way so I'm assuming it's in the rear end but cant make heads or tails of as it's ONLY when downshifting. No chatter, no noise, nothing abnormal under the head. Truck still runs, drives, brakes, and overall has no problems. Just this noise. Any advice on where to look will be greatly appreciated. Thank you!

Not to discount your rear end concern, but a change in engine speed can sometimes cause momentary drive belt slippage on a loose or aging belt. Have you checked them for looseness or cracks?

 

[glockholiday]

Is it a belt slipping with the sudden jump in rpm. How old are your belts, how's their tension.

 

[83greenbean]

Belts are no older than 4 years. The mystery notice is noticibly coming from the rear of the truck. Truck has maybe 20000 miles on engine and gets maybe 500 miles a year on it. I've used the "belt reconditioning" jazz from Lucas oil and the tension and conditions of the belt seem to be that of good condition. I'll double check the belt again just to be sure. Thanks folks. I do appreciate it.

Also, this noise has no noticeable effect on the truck, I just like to prevent squeaks from Turing into grenades lol
Not sure if that info helps or not.

 

[Georgeb]

Is it a Manual trans?

 

[83greenbean]

It is a manual transmission. I made sure everything that needed greased was, I smacked on my drums with a hammer a touch and one of the two was my culprit. No more squeak. Thanks guys. I do appreciate the help!