I need some opinions my ring gear. (1 Viewer)

[toddm]

Hi All,

I have my rear 3rd member apart due to a lot of rumbling noise from the rear end ( I think). I have a 3" straight exhaust on the diesel engine so its difficult to hear whats going on. I have had a rumbling sound from the rear end at about 45MPH for a while now. I don't drive the 40 very much but recently I've had it out a few times. My last trip 60 miles or so the noise got much worse with a fair amount of vibration such that I was inclined to keep it below 30MPH as I neared the house. Last night I disassembled the axle and the 3rd. There is significant pitting from rust on several teeth on the ring gear. The Pinion looks ok to me. I expected to find some trashed bearings but they all look pretty good too with the exception of a small amount of tiny little pits that look like they are from oil contamination. The races on the pinion bearings look a little dull and I can see some very small pits in them.

Does any of this sound like it would have caused the noise or should I look elsewhere? It wasn't a whining noise like I had on the 4-runner from a bad small pinion bearing. It was more of a rumble which seemed to get louder if I let off the throttle.

 

[deliverance]

How’s the driveshaft/u-joints?

 

[Cruiserdrew]

Your ring gear may work for awhile but it's done and will just get worse over time.

Rumbling sounds like a bearing, and usually the outer pinion bearing which you can't see. You can't really see the inner one either.

If you want to try and use this, measure the pinion preload, Then run a pattern with gear paint.

But if it was me, I'd get a new gear set and a rebuild kit and have the differential rebuilt. That one is done.

I agree with checking the rear U joints as well.

 

[Drake2]

If it were me, a complete rebuild kit with new R&P set would be on order. If this is not a daily driver I would still do a complete rebuild but you could get away with a decent used (new to you) R&P set that does not have the pitting. I agree with the others as far as checking the U-Joints or just replace out of caution, they are not expensive..........especially to be broke down on the side of the road.

 

[toddm]

Thanks for the replies. I'll check the driveshaft, Its actually a double-cardan from a mini-truck. It felt like it might have had a clunk but was hard to isolate with the wheels in the air.

I am thinking of re-gearing anyway since it seems to lug the engine a little in 5th. I'm not sure how far I should go though.

 

[65swb45]

When was the last time your transfer case was serviced?
I just rebuilt a ‘78 transfer case for a local customer last week that had a rumbling sound.

The case had been run low on oil at some point, and the low speed output gear was walking off the bronze bushing and starting to kiss the inside of the transfer case housing.

And fwiw, I’d toss that 3rd in favor of a low mileage used front 3rd and just call it good. Just swapped one of those in another ‘78 about 3 weeks ago.

 

[toddm]

I rebuilt the t-case many years ago, but the last time I was in it was about 10 years ago when I hung it off of the NV4500. It certainly would be worth a look. It only has a few thousand miles on it but I suppose I could have left something loose. Thanks for the tip!