SCENARIO:

I've just rolled to a stop in neutral. I depress the clutch, and while depressed, select 1st gear.

'CLUNK' from the rear end.

I keep the clutch in and select 2nd gear.

'CLUNK' from rear end.

I can go back and forth between 1st and 2nd and keep getting the clunk. This doesn't ALWAYS happen, but it has been sometimes. I get a similar noise if I let off the throttle, and then get back on it quick.

RESEARCH:


The U-Joint straps at the rear pinion were a bit loose so I tightened those up. I think the freeplay in the driveshaft seen in the video is normal, but it's the u-joint near the yoke that seems suspicious.

At ~30sec into the video, you can see that there is some lateral play in the upper u-joint, and the yoke itself is moving too.

Could that be where my 'clunk' is coming from?

PS I haven't checked the rear diff fluid level, but plan to tomorrow.

PPS My DS is at about 12°, and the rear pinion and transfer case yoke are within a few degrees of parallel.

Thanks!

EDIT: you can hear me sighing as I try to hold the camera steady while wiggling the driveshaft. It's easier to see the movement if you watch the yoke

 

If you are getting "clunks" while the clutch is pushed in, then your clutch is not completely disengaging and the disks are still rubbing somewhat.

As for the clunk in the video, most diffs will do that with some age on them. Once you get a little wear on the teeth of the gears and some wear on the bearings you will have a little slop that makes that clunk. I have it on both my 85XJ(150k miles) and my 96 F150(256K miles) If it was so tight there was no slop, it would be too tight and quickly wear out the gears and bearings. But if you can move the pinion yoke up and down or side to side, then the pinion bearing is getting bad and will cause more noise, or if the U-joints have any play in them they are worn out, they should actually be quite tight.

The front slip joint/yoke should have just a little play as it ages, but that U-joint should not. Might be a good idea to replace both U-joints and see if some of the noise goes away, but I imagine there will still be some clunk when you first put pressure on the driveline.

 

Thanks for the response, exactly what I was looking for! I am new to this stuff so everything helps.

I had thought that about the clutch as well, that somehow when I was shifting power was still being transmitted through the driveline to the rear. I suppose I'll do some more research in to adjusting the clutch, I'll add it to the list