A bit of help please

[blackpoolsparks]

Sorry this is a bit long winded, but I need to thoroughly explain the fault.

My KZN185 has developed a problem, where by when I reach a speed of 55 and over, the truck vibrates. The best way I can explain it is it feels like I'm driving over a grooved surface. The faster I drive the more pronounced the vibration. Oddly enough, when I remove my foot from the accelerator, or put it in neutral the vibration increases dramatically.
I had notices a leaking front seal on my centre diff. and assumed it was related. I had it to a garage today, as I'm rather busy and they could not find anything physically wrong with the drive components and checked all the oil levels of the diffs.
To no avail.
I then thought that it might be related to the transmission as it does clunk a bit when engaging from neutral to drive or reverse. Level was a tad low, bottom of the scale, the colour was nice and red and no smell of burning.
I also sometimes hear/ feel a slight knock when setting off from a standstill.
I'm not really sure what to look at next and my thoughts are that I'm going to use a process of elimination, i.e. remove front drive shaft, try, replace, remove rear, etc.
Only one other thing to mention.
This fault has only started after I recently fit a 2" suspension lift. Double checked everything and all is tight. Coincidence maybe ???
Any thoughts would be much appreciated.

Sparks...

[TonyN]

could be the front drive shafts, they are running at a different angle now.

are the UJ's all ok? its often not enough to feel for loose ones, take the shaft off and check for tight ones by flexing it by hand.

I've had lots of issues on 3rd gen with worn steering joints, that you tend not to notice untill you lift it, it exaggerates the wear and it suddenly becomes more noticeable. so check your tierod ends and rack bushes.

also check your tyres for ovalness.

[blackpoolsparks]

its other not enough to feel for loose ones, take the shaft off and check for tight ones.
.

Im assuming this translates to:
its OFTEN not enough to feel for LOOSENESS, take the shaft off and check for TIGHTNESS

am I right?

The tyres are nearly new, only have had them on for a 1000 miles tops.

Thanks Tony, I'll have a look see at weekend
and
its good to know youve experienced similar issues when lifting 3rds before

Thanks
Gordon...

[TonyN]

Im assuming this translates to:
its OFTEN not enough to feel for LOOSENESS, take the shaft off and check for TIGHTNESS

am I right?

don't want to make things too easy for you, you have to work for the answer

Don't rule out your tyres, if they are going to delaminate under the tread, they will do it not long after you start using them, but it probably isn't that, but dosn't hurt to bring it up.

Did the tyres go on when you did the lift or before?

More likely to be drivetrain related though, especially as it dosn't go away when changing engine load or revs.

[blackpoolsparks]

The tyres went on a before the lift.
How do i check for delamination?
is it clearly visible?

As you say, i think its drivetrain related

[TonyN]

I had a nearly new BFG A/T that did it, you could spin it and see tread go up and down as it turned, as if there was a lump under the tread.

Try swapping tyres round, my duff tyre was much less noticable when switched from front to back axle.

But still more likely to be CV'S or UJ's to me

does it change in 2 or 4wd?

[blackpoolsparks]

tried that (4WD and 2WD)
no difference

[blackpoolsparks]

Bump for Kerrsurf

[KERRSURF]

Take the rear prop off and see if it disappears, help you rule stuff out.

Prop off/no vibration then rear prop/rear diff problem.

Prop off/still vibration then problem at front end, driveshafts/diff/front prop/steering setup.

[KERRSURF]

Or tire problem, or wheel bearings or ball joints?

[TonyN]

You can also take the drive shafts out and drive it to rule out CV's.

[KERRSURF]

When the uj gave up on my rear prop it was only the noise that gave it away, going by feel told me nothing. I didn't have any vibration however, just a nice squeal when I reversed truck.

[blackpoolsparks]

thats my plan
problem is its about 15 mins to the motorway from my garage, lol

[TonyN]

When the uj gave up on my rear prop it was only the noise that gave it away, going by feel told me nothing. I didn't have any vibration however, just a nice squeal when I reversed truck.

Yeah, thats why I always say take them off and try by hand, wiggling on the truck only shows looseness, I've seen lots that are stiff and dry and not long for this world in that condition.

[KERRSURF]

Yeah, thats why I always say take them off and try by hand, wiggling on the truck only shows looseness, I've seen lots that are stiff and dry and not long for this world in that condition.

The needle bearings fell out of mine like dust! lol.