Diff noise on deceleration-pinion preload?

[tooch]

Just trying to sort out the noise from my diff on the hilux surf I just bought.
Basically, its a very loud humming/howling sound which only occurs on deceleration. Basically when you lift right off the throttle and coast, it does it. The second you get back on the throttle or push the clutch in, it goes away.

From the research I've been doing, it seems that it could be caused by the pinion pre-load being too loose. Does this sound right? And is there any easy way to check it, can I basically unbolt the prop shaft from the diff and see if the pinion shaft has play in it? Or am I completely off track here?

I'll check the diff oil tomorrow, as I wouldn't be surprised if there isn't any

[cambelt]

Yep grab the tailshaft and see if theres any up and down , if not the diffs prob buggered.
Dave

[clubagreenie]

I had this once (in range rover) and turned out to be the bearing cap bolts were loose. Under forwards load pushed everything into place, on overrun, would force it to move and misalign the crownwheel against the pinion.

Was fun to fix on the side of the Great Western Highway, outside Lithgow jail in july. Especially walking into town and back for oil.

[blacktop]

does it only happen when its hot?

It sound as if your on the right track

I don't know of any way to test other than getting under the car and seeing if there is any movement in the shaft when put under load, even then you probably wont see anything.

[tooch]

Nah happens at all temperatures.
No real movement by grabbing the driveshaft, just a bit of up and down (maybe a mm or so). That's up and down as in between the road and floorpan not between diff and gearbox. Should there be any play there at all? May have to unbolt the driveshaft frm the diff and see how much there is when the shaft is removed.

[blacktop]

You might need to take the shaft off and check if there is any play with the depth (in and out like the pinion is screwing the diff)

[cambelt]

If theres a mm or so you have to tighten it up a little bit with the big nut first ( JUST NIP IT UP TO TAKE THE PLAY OUT) then put the tailshaft back on a take it for a spin .
If the noise is still there then you have to remove the diff center and check further. If the noise goes away then you have to reset the pinion preload and put a new seal and shim in there.
Dave