So when I'm up to speed and I let off the gas and let my truck coast, I hear a howling sound and it quiets as I slow down or come to a stop. Seen this video and that is exactly how mine sounds, timing and all. Although the truck in the video Im not sure if it applies to my '95 jimmy 4x4. Do I have a pinion preload that needs tightening ?

 

There are a lot of very specific measurements that go into the rear differentials to make the ring and pinion mesh properly. Dont just start trying to tighten the pinion nut or messing with stuff unless you know what you are doing or you will destroy the diff.

Having said that, Have you taken the cover off yet and inspected the ring and pinion?
If you grab a hold of the pinion where the driveshaft mount, can you move it at all other than rotation?

 

No I haven't touched the rear end. Which way is rotation?

 

The pinion yoke should spin with the driveshaft (rotation) and thats it. It should not wiggle up and down or side to side at all.
You can also pull the cover on the rear by removing the 10 bolts but be ready to catch the fluid.
!!!!BEFORE you remove that cover, make sure you can remove the fill plug located on the passenger side of the center section. it looks like a square drive plug and a 3/8 ratchet and extension fit in to remove it.!!!!
If you cant remove the fill plug, you may have to take it to a shop and have them remove it with some additional tools.

 

OK I'll check it out, although those bolts look very rusty. I also noticed it is leaking slowly. No drips or puddles on the ground, but sitting on the underside of the rear end.

 

Seems like the rear end leak is coming from where my drive shaft connects at the U bolts and the rear end piece... is there supposed to be a gap right there?

 

That looks fairly normal and the nut holding that yoke on to the diff has a high torque value and very rarely loosens on its own. You need a pinion seal to fix that leak, and watch a couple u tube videos , Is is a pretty easy job.

 

Yep bad pinion seal, but to replace it properly you will need to remove the pinion nut and yoke then replace the crush sleeve and reset the pinion depth and Ring and Pinion mesh.

Take it to a shop that specializes in differentials if you want it to be a lasting fix.

 

OK will do. Would this affect my drivability and decrease my acceleration?

 

As long as you keep the fluid full and the pinion nut is not loose all it will do is make a mess.
but you have to keep checking the fluid to make sure it full or you risk burning up the rear end.


However if it has been ran very low or empty then yes that could affect drivability because it will destroy the bearing in the rearend.