Random rear diff noise?

[oldschoolsdime92]

Recently, I've noticed my dana 35 making an odd whine, or hum. Only when the throttle is very lightly applied and stable, say 35 mph in 4-5 gear. Hard acceleration it goes away, as does coasting. I'm thinking bearing. I changed the diff fluids about 2000 miles ago. Ring and pinion looked fine at the time. Any thoughts?

 

[Jerry Bransford]

Well, it's hard to say without hearing and driving it. If it still has the stock gears, it could be (and most likely is) a bad bearing. If it has been regeared in recent history, it could be whining from a bad gear setup as happened to me after one of my regearing jobs.

 

[Rob5589]

Generally; whine under acceleration = rear pinion bearing; whine under decel = front pinion bearing; whine under steady, even load = ring and pinion whine. Of course there could always be a combo of all of those. If your R&P is now starting to whine it could be due to bearings being bad and throwing off the set up.

How many miles do you have on it?

 

[oldschoolsdime92]

Rolled over 206k today.

 

[Stinger]

Like Jerry said--has it been redone? With 206k my guess is pinion bearing.
Good luck.

 

[oldschoolsdime92]

No, it hasn't, but I have a feeling its going to get redone sooner than later.

 

[oldschoolsdime92]

If I'm going to end up having to rebuild the diff, I'd like to regear. I pull a 6x10 trailer with a zero turn on it once in awhile. She doesn't like that with her current gearing. Whats the lowest gear I can go with on the stock carrier? The jeep has 3.07s now.

 

[Rob5589]

The 35 carrier will need to be swapped, 3.31 and down, 3.55 and up. The front will also have to changed, 3.54 and down, 3.73 and up. What eng/trans combo and tire size you running?

 

[oldschoolsdime92]

4.0 5 speed with 3.07s

I went through the diff last night. Oil is clean, no pinion slop, no broken teeth. No slop anywhere I could replicate in the diff. Axles don't slide in and out with any notable movement.

But I did find this at the slip yoke. Is that normal?

 

[Rob5589]

It does not look excessive. There is going to be some movement/slop especially with 200K + miles. Chain stretch, gear wear, etc is unavoidable. What tire size are you running?

Here is a great calculator: http://www.grimmjeeper.com/gears.html

 

[oldschoolsdime92]

31x10.5. Stock height.

URL]

 

[oldschoolsdime92]

It does not look excessive. There is going to be some movement/slop especially with 200K + miles. Chain stretch, gear wear, etc is unavoidable. What tire size are you running?

Here is a great calculator: http://www.grimmjeeper.com/gears.html

Thanks, I just didn't expect any vertical movement there. I knew it would slide in and out with the suspension but wasn't sure if that was normal vertically

 

[Rob5589]

Nice looking Jeep. I really wanted blue (my fav color) but couldn't find one. Seemed to be a rare color, around here at least. Anyway, it is just wear. Add up minute amounts of wear between the chain and gears, splines on the yoke and output shaft, u joints, etc and you are going to have movement. Looking at the calc, 4.10 will put you around 2700 at 70, 4.56 would be about 3000. IF you never increase tire size the 4.10 would work well. But, if you even have the inkling of going larger, 4.56 or 4.88 would be better.

 

[oldschoolsdime92]

Thanks. I'll just chalk my noise up to wear then.

 

[oldschoolsdime92]

After thinking about this for a few days, I believe the noise has always been there. I've just had the top off for the last 3 months and not been able to hear it. Once I put the top back on, I could hear about more mechanical noise than I had been able to in the previous 3 months of cruising. It also seems far less prevalent once everything is warmed up a bit.