Questions about differential rebuild (1 Viewer)

[Super77]

I'm getting a rhythmic soft grinding/brushing noise that I can hear at low speeds. At higher speeds, wind and road noise mask it:

- It feels like it's coming from behind me.
- It's variable with speed.
- At the low speeds when I hear it, I can silence it by shifting from D into N. Coasting in N = no noise regardless of engine RPM.
- The noise is present whether or not I am braking.
- The noise is there in both 2WD and 4WD.

Other potential clue: I get a slight "thunk" shifting from P into D or R, and a similar thunk on occasional downshifts.

My mechanic suggested it's a front wheel bearing, but if that were true, I should be able to hear the noise while coasting. I am thinking driveline: U-joint(s), differential bearing, or slip joint (the thunk). If so, what's the best diagnostic process to determine which? I'm reading up on lubrication here.

Thanks!

 

[micruz60]

Probably a u-joint.
Jack up the rear end and spin a tire, with trans in neutral, watch the driveshaft at rear pinion for play, also refer to fsm.
hth

 

[Super77]

Probably a u-joint.
Jack up the rear end and spin a tire, with trans in neutral, watch the driveshaft at rear pinion for play, also refer to fsm.
hth

My memory is a bit murky on this, but when I replaced the U-joint on my 40 many years ago, I was getting a sharp snapping/ticking noise with a more random pattern. This is more of a softer, steady "thrum-thrum-thrum.."

 

[micruz60]

Pinion bearing is next on the list.

I had a similar noise and vibrations as well, and it was the PB as well as the rear u-joint.
I did run close to 10,000 miles on it before changing it.... Started to get gear oil splatter from the pinion.

eta: what does the diff gear oil look like?

 

[Super77]

I jacked up the ass end and watched/listened underneath with the trans in D, at various RPM. I could not reproduce the noise. When stopped, there was probably 4" of rotational movement at the rear wheel before seeing the driveshaft move. Is this a normal amount of play? There was no visible play in either U-joint on the shaft. Gonna check the fluids shortly.

One thought: has anyone ever removed the rear drive shaft and driven with just the front wheels engaged? This might help isolate the problem.

 

[micruz60]

Search is wonky, but I found this:

Strange noise that I cannot figure out...

 

[LAMBCRUSHER]

remove shaft and check pinion flange and tcase flange for up-down/side to side play...do you run a lifted spring or add a leaf?

 

[Super77]

remove shaft and check pinion flange and tcase flange for up-down/side to side play...do you run a lifted spring or add a leaf?

I'm on the lightest of the OME springs. Probably 1"+ compared to stock, same # of leaves. FWIW, this noise has been there since I got the truck 8-9k miles ago, and it was sitting on the clapped-out original suspension most of that time. What I haven't done yet since I got it is to check the tcase/diff fluids and driveline lube points.

 

[DirtRoads]

U joints can make a lot of funny noises. I'd put my money there. Pull the rear shaft and wiggle check everything

 

[micruz60]

Ah yes, suspension changes will affect driveline angles, also, I did not notice it before, but this is an auto trans, and the clunk when shifting ? IDK... Other Atrans issues?

I doubt your drivelines are out of phase? Something to check.

 

[SteveH]

My mechanic suggested it's a front wheel bearing, but if that were true, I should be able to hear the noise while coasting.

Front wheel bearing noises often change when you side-load them, such as by swerving from lane-to-lane. And, if it's loud enough to hear when driving, it'll be audible/sense-able if you jack up the front wheel and spin it by hand.

 

[Super77]

Retitling this thread since it's heading a different direction.

This weekend I pulled the rear driveshaft to check for play in the rear drivetrain. The shaft itself looked good - both u-joints were solid and no play in the spline joint. I blew the old grease out and replaced with fresh MP lithium grease. Also changed the gear oil in both differentials as well as the transfer case. No change in the soft rhythmic "growl" coming from the rear end.

With the rear shaft removed, the connecting flange on the rear differential has about 1mm of side/side and up/down play, plus a couple of cm of backlash. Also has a gear oil drip in that area, with a noticeable spray pattern on the underside of the body. It's been slinging oil for a while. My money is in the pinion bearing(s). Certainly the seal needs replacing.

So here are my questions for those who have done this work:

1) Rebuilding the differential might make sense. I'd rather work on a bench than upside-down on the floor. This one or this one appear to fit the need. Any thoughts or better alternatives?

2) Would buying a rebuilt differential be cost-effective? I'd like to know that the ring and pinion have been properly set up.

3) Just for shirts and giggles, could I just swap the front and rear differentials? Not a long-term fix, but buys me some time.

Thanks!

 

[John McVicker]

If you rebuild it yourself, you might ad Terirain Tamer to you selection of kits. I believe both Georg and Cruiser outfitters sell this kit.

 

[lovetoski]

A couple of thoughts...
You can swap the front and rear diffs, and that will buy you alot of time. It also means a lot of work to pull both diffs.
The diffs have a crush sleeve behind the pinion nut. And I believe (might be wrong) that to replace the seal you have to remove the nut - and getting the nut and crush sleeve torqued right requires having the diff on a bench.
I put a used diff in the back of my 80 at 250K and did the same with my 60, when both had failing pinion seals. Since they fail slowly, you can search for a good used on at a good price.
Finding a front diff to replace a rear diff is a great option - it's a cheap way to get a nearly new diff in the rear.

 

[Super77]

A couple of thoughts...
You can swap the front and rear diffs, and that will buy you alot of time. It also means a lot of work to pull both diffs.
The diffs have a crush sleeve behind the pinion nut. And I believe (might be wrong) that to replace the seal you have to remove the nut - and getting the nut and crush sleeve torqued right requires having the diff on a bench.
I put a used diff in the back of my 80 at 250K and did the same with my 60, when both had failing pinion seals. Since they fail slowly, you can search for a good used on at a good price.
Finding a front diff to replace a rear diff is a great option - it's a cheap way to get a nearly new diff in the rear.

Hey Doug! Thanks for chiming in. I dropped in on Tor and he basically told me the exact same thing you did. He can get me a used 4.11 front diff that I can drop in back. I think this is the way to go. I'll then have a spare that I can fiddle with.

One thing he said threw me off: typically, failing pinion bearings will make MORE noise when coasting, and you can hear them pretty well. Mine is very soft, and it completely GOES AWAY when coasting. Wondering if I should look at anything else before I spring for the replacement diff.

 

[lovetoski]

Hey Matt,

The failing pinion bearing on my 80 did make more noise when coasting.

Tor knows way more than I do about landcruisers. He's not omniscient, but close.

One option is to keep driving, and see how the noise changes over time. My experience is that landcruisers give you lots of warning before they fail. As long as you have AAA...