Land Cruiser 100 Thump Noise

[DarmeshP]

Hi there ,

My Land Cruiser V8 4.7 1999 Model Automatic.

AHC system.

When I raise or lower my suspension I hear a Thumping noise under the car.

First I thought that it would be the shocks or coils being dry or stiff.

Changed the shocks, and the noise continues. checked if the suspension coils were broken or out place, all ok also.

With a little bit more attention, trying to listen from where the noise is coming, me and the mechanic noticed that its coming from the rear Diff.

And its noisy only when in D, R, or P. When in N Neutral not making that noise. the noise is like thumping.

When driving and braking sometimes I hear that same noise.

What can be the problem ?

 

[BobMurphy]

Hi, and welcome to the site.

This sounds most peculiar, could you just clarify a couple of points please . .

1. Is the 'thumping' sound happening while the suspension is raising or lowering (or when you are driving AFTER the suspension has been raised or lowered)??

2. "It only happens in D, R or P" - Are you sitting in the car, with engine running, brakes on, in 'D' (for instance) while altering the suspension height, or is the car moving (not in 'P', obviously)??

3. Just confirm, please, Transfer Box in 'High Ratio' and 'Centre Diff Lock' NOT engaged??

4. you say the 'shocks' were replaced. The four 'Struts' are not shocks - they are just Hydraulic Rams. The Shock Absorbing comes from the four Actuators (with the Suspension Globes attached) on the chassis. Was it the Rams or the Actuators that were replaced ??

If the noise is definitely coming from the rear differential it sounds as though some vibration is being transmitted via the rear propshaft. I would be inclined to disconnect the propshaft from the rear diff (four tight bolts!) and see if the noise persists. That would only be appropriate if the noise occurs while the car is stationary of course!

An interesting one, this .

Bob.

 

[DarmeshP]

Hi Bob,

Thanks for your reply.


1. Is the 'thumping' sound happening while the suspension is raising or lowering (or when you are driving AFTER the suspension has been raised or lowered)??
Reply ; Its happening while im stopped raising and lovering. And also happens on my normal drive sometimes, while in Normal Height.

2. "It only happens in D, R or P" - Are you sitting in the car, with engine running, brakes on, in 'D' (for instance) while altering the suspension height, or is the car moving (not in 'P', obviously)??
Reply : D,R,P stopped, while rising and lowering. Also happening when I rise or lower during the drive. Seated in the car. With and without Brakes On.

3. Just confirm, please, Transfer Box in 'High Ratio' and 'Centre Diff Lock' NOT engaged??
Reply : High Ratio yes, Diff Lock not engaged.


4. you say the 'shocks' were replaced. The four 'Struts' are not shocks - they are just Hydraulic Rams. The Shock Absorbing comes from the four Actuators (with the Suspension Globes attached) on the chassis. Was it the Rams or the Actuators that were replaced ??
Reply; I have replaced 4 shocks ( Here its called Shock Absorbers ).


If the noise is definitely coming from the rear differential it sounds as though some vibration is being transmitted via the rear propshaft. I would be inclined to disconnect the propshaft from the rear diff (four tight bolts!) and see if the noise persists. That would only be appropriate if the noise occurs while the car is stationary of course!

An interesting one, this .

Bob.[/QUOTE]

 

[BobMurphy]

I suspect the noise isn't coming from the AHC System, but from the rear suspension as the chassis-to-rear axle orientation changes (it happens when the suspension moves as well, so is relevant to "driving with the suspension at Normal height".

The back axle is supporting the chassis via the rear springs - which you have checked. The axle is attached to the chassis by two pairs of Control Arms and a 'Lateral Control Arm' (also known as a Panhard Rod).

The upper (short) and lower (long) control arms have rubber bushes at each end. If these bushes wear the axle can move and tilt. When driving, there is often a definite 'clunk' as you go on and off the power when the Control Arm bushes are worn (I used to get that on a Volvo Estate). This happens when the axle tilts forward and back and the worn bush clonks against the mounting bolts.

Raising or lowering the suspension could be having the same effect.

As a next step, I would have a very careful look at the bushes in the Control Arms, including the Lateral one. Sound will be carried into the axle casing which could be why you think its coming from the Differential.

Let us know what you find .

Bob.

 

[DarmeshP]

Thanks Bob.

Will check and come back with a reply.

 

[CANEX]

Did you have any luck finding your 'clunk'?
I have a similar one & can't find it either.

cheers
Chris

 

[frank rabbets]

The rear prop shaft is telescopic and changes length as the suspension goes up/down. A dry/ungreased joint may well clunk.

 

[CANEX]

I thought that as well but have had mine greased & it still clunks

 

[frank rabbets]

Silly question. You did grease the sliding joint not just the yolk joints?

 

[uHu]

It is more common to get a clunk when overdoing the greasing of the splines on the prop-shafts. The oil seals are normally very tight, and by pumping in grease, you might get hydrolocking with constant force on the rear axle.
Try unscrewing the grease zerk/nipple and take it for a spin. If the clunk is gone - bob's your uncle; if not - check bushes etc.

 

[frank rabbets]

That's very true uHu. Even with correct an mount of grease in the shaft is much easier to slide and get the flange off with the nipple out.

 

[CANEX]

I didn't grease the prop myself so I'm not sure how much grease was put in but I asked them to fill it until it came out at the joints as all the forums seem to suggest. I know you aren't supposed to on the 80's but on the 100's it is recommended.

 

[frank rabbets]

If you're talking about the sliding joint there must be an overflow/escape hole somewhere?

 

[frank rabbets]

I remember now that the english cars I worked on had a hole in the centre of the prop shaft end plate so grease would come out when the prop was full. Perhaps they forgot to drill the hole on the 80's.

 

[uHu]

There is no escape for the grease in the splines, other than through the oil seal. Don't put in more than 3 strokes with a hand pump.
For the UJs the grease will come out easily, after about 2 pumps.