Need help diagnosing front end clunk (1 Viewer)

[WVFJ60]

Looking for some assistance in figuring out a front end driveline noise. I tried searching for some other threads with similar issue but couldn’t find anything that matches my situation exactly yet. Thanks in advance for any insight anyone can provide.

1996 FZJ80 - 245k miles - Unlocked

I have a very distinct, metallic clunking sound coming from the front end. I suspect it is driveline related as I just replaced the suspension and have double checked loose bolts and such. It also doesn’t happen over big bumps, mostly when going over washboard or rocky, dirt roads. I notice it only when coasting, not while on the gas. I just did a full knuckle rebuild thinking that was the issue but that changed nothing. The birfield joints looked good. The drive flanges were in good shape as well and no worn teeth. The only thing I noticed was there was some rotational play in the shafts when I reinserted them, like they weren’t engaging the teeth in the diff, but couldn’t turn the shafts all the way around. There was no metal in the drain plug. I also just greased drive shafts and yokes. I’m assuming my next move is to pull the front third member and see if anything is broken but wanted to see any other possible things to try first.

 

[Shipwreck]

Before you tear into the diff, I would take a second look at your shocks. Make sure the bushings and washers are seated and installed in the correct order. Pretty easy to have a top nylock nut tight, but not seated down to the bushing.

 

[WVFJ60]

Before you tear into the diff, I would take a second look at your shocks. Make sure the bushings and washers are seated and installed in the correct order. Pretty easy to have a top nylock nut tight, but not seated down to the bushing.

Checked the shocks and they seem to be seated and tight as I couldn’t get them to move around or anything. I also had this noise before installing new suspension as well.

 

[WVFJ60]

Is this too much play in front end with one wheel off the ground? This sounds identical to the clunk I hear while driving

 

[Anvil]

I had this problem once. The brake caliper bolt was missing, putting the caliper/pads in a bind.

 

[ceylonfj40nut]

Is your front drive shaft moving when you do this?

 

[WVFJ60]

Is your front drive shaft moving when you do this?

Yes, it rotates just a small amount, not as much as the wheel does.

 

[mudgudgeon]

Yes, it rotates just a small amount, not as much as the wheel does.

Drive shaft should rotate 4.1:1 times what the wheel does. 3⁰ rotation of the wheel would be 12⁰ ish at the driveshaft.

That been said, you probably rotating the wheel maybe 1 or 2⁰.

I can see hear a bit of slip in the drive flanges, maybe a bit more than ideal, but it doesn't look excessive to me.
You could pop the dust cap off the end of the hub, and watch how much slop there is in the Birf/drive flange splines.
Splines should have nice sharp shoulders on the edges of teeth, not vague rounded peaks ( red lines) You should see a well defined edge ( orange lines)

Shape of the splines at the exposed/ unworn end of the Birf should be consistent right along the length of the splines. If these or flange splines have rounded peaks, its probably time to change them.

You said you greased uni joints. Did you remove driveshafts and inspect the uni n joints?
It's really difficult to gauge their condition while they are bolted in the truck.
With them out, you should be able to rotate uni joints freely in all directions. Any looseness is no good. Sticky or notchy rotation is no good. Not being able to rotate them through the full range of motion is no good.

I'd recheck these before looking further.

If splines and unis are good, then maybe investigate the front diff.
The heavier clunk in your video may be excess backlash in the diff. Crush sleeves can collapse leaving incorrect preload on pinion bearings. And bearings can wear out and fail. This can cause a clunk.

But, I wouldn't leap to the diff being the problem without reassessing the cheaper, more prone to wear uni joints and birf/flange splines.

 

[WVFJ60]

Drive shaft should rotate 4.1:1 times what the wheel does. 3⁰ rotation of the wheel would be 12⁰ ish at the driveshaft.

That been said, you probably rotating the wheel maybe 1 or 2⁰.

I can see hear a bit of slip in the drive flanges, maybe a bit more than ideal, but it doesn't look excessive to me.
You could pop the dust cap off the end of the hub, and watch how much slop there is in the Birf/drive flange splines.
Splines should have nice sharp shoulders on the edges of teeth, not vague rounded peaks ( red lines) You should see a well defined edge ( orange lines)
View attachment 3714174
Shape of the splines at the exposed/ unworn end of the Birf should be consistent right along the length of the splines. If these or flange splines have rounded peaks, its probably time to change them.

You said you greased uni joints. Did you remove driveshafts and inspect the uni n joints?
It's really difficult to gauge their condition while they are bolted in the truck.
With them out, you should be able to rotate uni joints freely in all directions. Any looseness is no good. Sticky or notchy rotation is no good. Not being able to rotate them through the full range of motion is no good.

I'd recheck these before looking further.

If splines and unis are good, then maybe investigate the front diff.
The heavier clunk in your video may be excess backlash in the diff. Crush sleeves can collapse leaving incorrect preload on pinion bearings. And bearings can wear out and fail. This can cause a clunk.

But, I wouldn't leap to the diff being the problem without reassessing the cheaper, more prone to wear uni joints and birf/flange splines.

Thanks for all the info. I will certainly check the things you mentioned. Hoping to avoid digging into front diff so hopefully it’s drive flange or u-joints.

 

[WVFJ60]

Splines seem to still be good and I’m not seeing any slop in the flange but may not be looking for right thing

 

[mudgudgeon]

Splines seem to still be good and I’m not seeing any slop in the flange but may not be looking for right thingView attachment 3714209
View attachment 3714211

Your video looks spot on. No issue there.

FWIW, its the splines inside that flange that matter. Not the bit visible on the outside.

 

[Nad Aitch]

Shot radius arm bushing?

 

[WVFJ60]

Shot radius arm bushing?

Doesn’t seem to be related to a bushing since not all bumps make the noise or suspension movements induce the noise. I will double check them though.

 

[Broski]

The amount of movement seems normal the sound I hear does not.
I would remove the front drive shaft and drive it see if there’s any change.

 

[WVFJ60]

I pulled the front shaft and checked the u-joints. Front one had some binding in it so I replaced that one. Rear was fine and moved smoothly and freely. I could still generate the noise within the diff just by rotating the flange on back of front diff. Starting to think it’s definitely coming from inside there. Maybe the bearings or crush sleeve like @mudgudgeon mentioned. I did not drive it while front drive shaft was out but I’m guessing the noise would’ve still been there.

 

[BILT4ME]

I pulled the front shaft and checked the u-joints. Front one had some binding in it so I replaced that one. Rear was fine and moved smoothly and freely. I could still generate the noise within the diff just by rotating the flange on back of front diff. Starting to think it’s definitely coming from inside there. Maybe the bearings or crush sleeve like @mudgudgeon mentioned. I did not drive it while front drive shaft was out but I’m guessing the noise would’ve still been there.

That looks like an excessive amount of lash on the pinion.

You may consider tightening the pinion nut about 1/8" rotation CW. That's on the outside edge of the nut, not at the threads .