grinding noise? please help!

[61vettedad]

New member! New CJ owner! Great site!

I bought a 1985 CJ7 straight 6, 4 speed (new Transmission may 2009). This jeep has a 4" suspension lift.

The Problem is when I drop the clutch a little faster than normal I hear a loud grinding like slipping sound? I have done this in 1st gear and reverse testing it.

other than that everything is fine and it runs and drives great! but I am concerned about what is wrong?

could the 4" lift cause the driveshaft to do this? any help or ideas?

here is the jeep YouTube - 1985 Jeep CJ7 CJ 7
Thanks Scott

 

[CJ]

Hello 61vettedad and welcome to our site!

That is one NICE looking 7 you have there (and a nice trailer too)!

You have some good size tires on that CJ - they look like 33's... Does the sound come from the rear or the center or the CJ?

 

[61vettedad]

I would say from the rear of the CJ but not 100% sure. I had no one to look under while I did it except my 9 year old and he said it came from the rearend.

 

[Old Dog]

Well I have to say I have no idea. But I would check the motor and Transmission . mounts to be sure they are good as a start.

 

[CJ]

First thing I would do is pick the complete rear end up with a floor jack and check for noises by rotating the drivetrain by hand...

Unfortunately I bet that you don't hear or see any problems...

Your CJ probably has a flanged axle AMC20 rear end and I bet that the hub is slipping when you hit the gass hard and dump the clutch.

Put a mark on the rear axle hub / axle and try your test again... I bet they do not line up after that and the hub is slipping... That is one of the biggest mistakes that Jeep did.

Let us know after the 'mark' test...

 

[elwood blues]

Welcome to the site . That is a very nice looking CJ you picked up. I have to agree with both the Old Dog, and CJ. Check mounts, make sure nothing is bouncing around that shouldn't be, and do like CJ said for checking the rear end.

 

[CJ]

I'm betting on the hub slipping! Wanna wager a ten spot?

 

[elwood blues]

Nope

 

[CJ]

nope :d

lol!

 

[61vettedad]

(by saying Hub are you talking about the differential to axle area)

I marked the hub (differential) to axles and tested it again and the lines still line up... I inspected the area and it looks like the axles are spot welded to the hub (differential) but there is rearend fluid leaking there that I didn't notice before?

 

[elwood blues]

No, the hub is the end of the axle that the wheel bolts on to.

 

[elwood blues]

The model 20 rear axle in CJ7s have two piece axle shafts. If I understand CJ correctly, you are spinning the outer of the two shafts (aka hub)

 

[coldwater]

Hmmm......is that an AMC20 back there???

 

[Old Dog]

Ok than, can you get us a pic. of the end of the axle (where the wheel bolts on to) and a pic of the diff. cover. We can than tell if it's a AMC20 and if it has one piece axles or not.
Also see if you can tell where the diff. fluid is comming from.

 

[kicknjeep]

i'm gonna go with spinning hub if it is a AMC20 if not then maybe u-joint.

 

[61vettedad]

I will take pictures or video tonite and post them here.

lets assume that the hubs are slipping... now what?

rebuild the rearend?

Best place to buy the parts?

does anyone know of any links to similiar post here that can help me figure out what to do?
Thanks Scott

 

[coldwater]

I will take pictures or video tonite and post them here.

lets assume that the hubs are slipping... now what?

rebuild the rearend?

Best place to buy the parts?

does anyone know of any links to similiar post here that can help me figure out what to do?
Thanks Scott

Not the end of the world If It's a stripped out hub. Just pop the axle out and slide in a new one. I strongly sugget you go with a set of 1 piece axles though. The AMC20 axles is a poor design and is somewhat prone to breakage. A new set of one oiece shafts will cure that problem. They go for about 200 bucks.
http://www.quadratec.com/products/52401_07_07.htm

 

[61vettedad]

what about driving it easy the way it is for a while? is it bad for it, will it sieze the rear end?

 

[CJ]

Until we make sure that you actually have an AMC20 diff (a quick look at the diff cover will tell), I wouldn't drive it much.

1) If it's not the hub slipping you could do some real damage.
2) If it is the hub slipping and you strip it out completely, you could be stuck some where with a Jeep that can't make it back...

Here is a detail picture of the AMC20 diff. The cover is round and easy to distinguish...

If you look at #2a you can see how the axle and hub are bolt together. #1 would be the one piece axle kit.

(images from Morris 4x4)

 

[kicknjeep]

I have heard of the rear end making this sound when diff fluid was low, Just on the off chance.