Noisy Rear Axle

[Biotex]

I have been putting this off long enough, so I decided to determine once and for all where the cyclic humming noise was coming from. It definitely speeds up with mph, not rpm. Because the noise sounded so much like tire noise, I swapped in some different tires with no change. I also checked and adjusted the rear brakes with no change.

I finally decided to raise the truck on jack stands while running the engine and in 4th gear. I took the necessary precautions, and ran engine up to about 40 mph where the noise seemed to be the most prominent. Once the wheels were off the ground, I could definitely pinpoint the noise from coming from the pumpkin by putting my ear to the cover. sure enough, that was it.

I blocked the passenger side wheel, and repeated, and the noise was a bit louder plus there was an added tick to it.

Doesn't sound like a bearing, but I might be wrong. I'm suspecting the spider gears.

Nothing to do but pull the cover and have a look. I can't justify spending much on a D35, so may just replace the whole rear end.

 

I have a 90 YJ rear with 3.08's which I believe is the same axle, except the spring pads are an inch narrower Comanche is 42" c2c where the YJ is at 41".

Should just be a matter of swapping them. If all I find wrong is something like the spider gears, it would be easier for me to swap just those. For that matter, I suppose I could swap in the whole center section just as fast. Takes about 3 hours to set up gears.

 

Aren't these truck just so much fun? :doh:

 

 

[johnnyc]

Grab the yoke and see if it moves in and out excessively. If so, the pinion bearing may be bad. I had that happen to me.

[Biotex]

Yeah, thanks for the tip. I have set up gears a couple of time. It's not like I can do it in my sleep yet, but I can get it done. I have all the tools, including set up bearings. It's just challenging trying to do it with used parts. I'm not spending money on a D35, especially since I have that YJ one. I also have a disc brake 8.8 ready to go, but it has 3.54's so I may use it, and swap in some matching gears into the D30 up front. I can justify that expense. I was going to use the 8.8 in my rock buggy, but guess it can wait.

 

Just not in the mood for more down time. Just got her drivable, and wanted to get some road time.

[1987Comanche]

 Very curious to see what you find when you pop the cover.  Georgia has been waiting on diff parts from Motive Gear (via Advance) for a few months.  She's waiting on side gears/spider gears and the forging run was supposed to be mid April, then mid May, now mid June. 

  I'd also verify any parts compatibility via the axle tag (should be a 3.07).  In Georgia's case the side gears only interchange '91-'93.

[Biotex]

 Very curious to see what you find when you pop the cover.  Georgia has been waiting on diff parts from Motive Gear (via Advance) for a few months.  She's waiting on side gears/spider gears and the forging run was supposed to be mid April, then mid May, now mid June. 

  I'd also verify any parts compatibility via the axle tag (should be a 3.07).  In Georgia's case the side gears only interchange '91-'93.

Maura is a 90, and so is my spare D35. I would put used parts in, not new. No way I'd spend that kind of money on a D35.

[Biotex]

Update:

Popped the cover, and can find no visible damage to any gears. I found no new metal shavings either, since I only have a couple hundred miles on since changing it, I wasn't too surprised. Here is what I did.

 

Put up on jack stands, and ran her in gear without any oil in the rear, but the cover on. I noted the noise by putting my ear to the pumpkin. I can definitely hear the gears, but not too unusual, just noisy. Refilled with oil, and repeated. No difference I could tell, so I pulled the wheels off both sides along with the drums. Definitely took away some noise, but not the noise that concerns me. I could stop each side of the axle with my hand, so I can eliminate the axle bearings, because no change when I stop either side from spinning.

 

I have basically narrowed down the noise to the gears or bearing inside the pumpkin. I put my ear right next to the pinion bearing, and I would have to say that it is not the culprit. It is either the carrier bearings in the case, or the gears themselves. I'm still stumped, but since the gears and spiders appear ok, I might as well replace those carrier and pinion bearings huh?

[HOrnbrod]

You can always pack few tablespoons of sawdust in the diff as an additive. Will quiet it down for maybe 10K miles and give you some time to find an 8.8, 8.25, or a D44 to replace it with.   :thumbsup: