Rear end whine

ab46501

I have a 91 Marathon that I use as a hunting buggy.
Sometime last year I bottomed out and dented in the diffirential cover pushing it against the main ring gear. I did not realize there was a problem until I started getting a whine.

I took the cover off and drained the fluid. There were no large foreign objects but you could tell where the gear had rubbed the back of the cover. I pounded the dents back out of the cover so it would not touch the gear anymore and I cleaned it out with brake cleaner as best as I could. There was no obvious damage to the gear itself. The cover was reinstalled with RTV and I added 75-90 Mobil One synthetic gear lube back in. The whine is still there.

It is only in forward and not reverse. I have full speed in reverse and it is quiet as can be. It also only whines under load. When I let off the pedal and coast it does not whine.

So does this sound like a bearing or a gear issue?

I had been through a lot of water as well so I sent the motor off to EMP to be reworked and the motor bearing has been replaced so it is not that.

Thanks!

BGW

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ab46501

Bumping my own thread and hoping for some input this time. I have pretty well eliminated all other possiblities so what I think is that the large bottom gear got damaged/worn when the pan was dented in. My guess is that all the rubbing has effected the teeth in some way even though it is not visible to me. Also that is why it only does it in forward and not in reverse since the teeth would be moving a different direction and pressure would be on opposite sides.

Does anyone have any instruction on pulling the rear end apart? Also does only one know where to get a replacement gear at? I've seen the speed and torque gear kits for sale but I just want to replace with the factory gearing.

pitbulld45

THe rearend is real easy to take apart. You will need snap ring plyers and a axle puller. You can get the puller from Auto zone or some place similar. They will rent it to you. Be carefull when you pull the axle shafts the gears will fall out so put something under them in case they arent damaged. I think if it were bearings it would still make the noise when coasting.

ab46501

Thought I'd bring this up one more time before I get another rear end.

The problem is whine.

The symptoms are only in forward under load. No whine coasting. Whine free in reverse even under load.

I sent the motor off to EMP last year shortly after my original post. They reworked the motor and replaced the motor bearing so I dont think that is the problem.

I tore the rear end down and everything looks fine. I even flipped the main ring gear around to see if that would make a difference but it does not.

I really dont see how it could be bearing related since it only does it in forward.

Thoughts, suggestion, opinions?

Thanks!

crash12888

A whine in a gear set under load is due to the gear "lash" being out. It might have been knocked out when you hit whatever and now it needs to be set up again.
Try to look at the dent and see if you can tell what way, left or right the ring gear might have been bumped, then try to adjust it back just a very little bit. I'm talking a couple of thousanths.
I would think maybe a service manual would cover this but you will need a dial indicator with magnetic base.
The only other way is have it professionally set up.

ab46501

Good advice, that might explain it!

One thing I did notice when I pulled it apart was that the axle shaft on the passenger side pushed into the spider gears about 1/4 inch more than the drivers side did.

I did not think anything of it but the hit would have pushed the differential assembly toward the passenger side. The main ring gear just bolts onto the assembly so I think I need to move the whole assembly back toward the drivers side possibly?

Has anyone else who ever dropped the pan on the differential paid attention to the distance the axle shafts stick into the spiders?

ColbyKiller

I'm watching this one. Bump for you.

mtwain69

keep us posted on the outcome

ab46501

I took the rear apart again and checked it over.....there is no play in any of the gears as far as I can tell and I could not move them to one side or the other.

While I had it off the cart I spun the tires by hand a listened very carefully. The noise seemed to be coming from the input gear area.

I changed the bearings on the input shaft and put it back together. The noise did not go away but seems to have changed tone slightly which now makes me wonder if it is the input shaft?

Could the input shaft have been the problem this whole time?

madoc1

sounds like you have it narrowed down. since you already changed the input bearings, all that is left is the main carrier bearings and the intermediate ones. did you try spinning the axles when the input was out? i guess you could have some kind of strange wear on the input shaft gear tho. there is no way to set the lash on an electric cart. does this make a noise all of the time or only when on the ground (under load)

Attached Images

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