Outer Limits 4x4 Board

How have you got on?

Back from holiday!

State of progress:
New front engine mounts, and new transmission side 'mount' - no improvement.
New u-joints and balanced shaft - no improvement.
New extension housing - no improvement.

The rear transmission mount seems to be in good condition, although it may have sagged a couple of milimetres, but I haven't replaced it.

I did notice one of the bolts holding the extension housing on was a bit mashed from contacting the frame (I think because the transmission mount has sagged), so for now I have packed the mount with some washers (still quite close to the frame though). This certainly made most of the bad sounding noises go away. But I can still feel the drivetrain thundering away under load.

The last thing I can really think of to try is to fix the rear pinion angle. There's no doubt that the driveshaft setup is technically appalling, but for some reason I'm not convinced that it'll help much. I've got some contacts to try for custom rubber suspension bushes, so I'll see if I can get some more quotes.

Interesting. It sounds like we have very similar vibrations.

My vibration has all but gone away at speed since i replaced the diff (housing and all). I had a bad vibration at 80km/h that slowly went away and was non existant at bang on 100km/h then rapidly came back by 103km/h.

The new diff, most of all that went away but what remains is a vibration that sounds just like you describe. Heavy throttle from about 2000rpm in 2nd and 3rd leads to a good vibration. I run FWHub's on the front so that rules out any front driveline.

I run about 30mm lift and 33 inch tyres so nothing out of the ordinary. Chasing my vibration I have done the rear gearbox mount, output housing, changed complete rear diff assembly (housing disc to disc).

My next thing was going to be the rear driveshaft, failing that I don't know. I was also planning on putting the axles in the lathe and checking they run perfectly true. But to me, the vibration is before the crownwheel as it is a 'fine' vibration - ie something spinning fast, not a rough one like a wheel out of balance.

The worst thing for me is it is the vib's are worse at accelerating as explained above with the new diff but much better at speed. Tit for tat!

So basically I am lost.

Glen

Glen, have you tried taking the 'dynamic damper' off the extension housing? You never know... (Mine doesn't have it).

Most of my vibration is (on and off) from 20 km/h to 60 km/h, espeicially in lower gears, but I guess just due to more torque in lower gears.

I've been scouring the aftermarket suspension bush catalogues.

Looks to me that the landcruiser/patrol bushes are the same dimensions, except the centre tube is 10 mm shorter than the mitsi ones. And since there are many offset castor correction bushes available for patrol/landcruiser, I'm contemplating using thses and packing the centre tube by 5mm each side of the bush. Question is, will it work?

Anyone have a feeling about whether this is viable?

Note:
Patrol/landcruiser, outside diameter 60 mm, inside diameter 16 mm, outside shell length ~ 40 mm, centre tube length 50 mm.
Pajero, outside diameter 60 mm, inside diameter 16 mm, outside shell length ~ 40 mm, centre tube length 60 mm.

pjb wrote:I've been scouring the aftermarket suspension bush catalogues.

Looks to me that the landcruiser/patrol bushes are the same dimensions, except the centre tube is 10 mm shorter than the mitsi ones. And since there are many offset castor correction bushes available for patrol/landcruiser, I'm contemplating using thses and packing the centre tube by 5mm each side of the bush. Question is, will it work?

Anyone have a feeling about whether this is viable?

Note:
Patrol/landcruiser, outside diameter 60 mm, inside diameter 16 mm, outside shell length ~ 40 mm, centre tube length 50 mm.
Pajero, outside diameter 60 mm, inside diameter 16 mm, outside shell length ~ 40 mm, centre tube length 60 mm.

Are you referring to the trailing (control) arm bushes?

Depending on how costly they are - could be something to try for sure. You will loose some wheel travel in the rear with castor correction bushes.

It is a good theory however and will be intersting to see some results.

I have had a thought in the meantime. Could you remove the two most rearward bolts and somehow adjust the angle manually by welding in a wedge or something and taking it for a quick drive to see if it makes any difference???

I have a spare diff housing and am tempted to try this myself - cut off the mounts where the rearmost two bolts go in and make a new one milled for infinite angles and have a go.... (thinking as I go here!)

Hudson44: yes indeed - the rear of the rear control arms.

Yeah, I've been thinking about ways to jig it, but having visions of disaster when it breaks free under load

Anyhow, I think I can get a set of bushes for about $200... Hope they fit!

Glen, doesn't yours have a CV joint at the top end? So you want all the driveshaft angle at the CV joint end and hardly any at the u-joint end... That's how my looks at the moment, except there a u-joints at both ends.

Lose wheel travel? That's bad... How come?

Don't know if this is of anyhelp, but I run 4inch GQ coils and my pinion angle is 12degrees and my rear tailshaft is at 9degrees. No vibrations, except when the uni at the pinion end of the tailshaft is on its way out. i also run and adjustable panhard with gq bushes.

pjb wrote:
Anyhow, I think I can get a set of bushes for about $200... Hope they fit!

I did mine yesterday with standard offset. Apparently there are 60mm and 65mm OD bushes, so it may pay to check the diameter of your control arms. I would still be looking at how far offset the diff is left to right as a panhard rod definitely sorted mine out and i'd been chasing a vibration for quite some time. (all mounts, ext housing etc) Mine was never down low however, mine was at about 100km/h.

Yeah - I got the 60's...

Hudson, I remember reading your post about the GQ panhard rod; how did you measure your driveline angle by the way? I thought most people measure the tyre-to-frame distance and equalise that...?

Incidentally, the vibrations are worse on right-hand corners than left-hand.

I didn't measure the pinion angle itself although looking at the back of the vehicle you could tell the diff was sitting to one side. I happened to have a spare GQ panhard rod lying around work so i re-bushed it and hoped for the best. Turns out it was almost perfect for the amount of lift i have. The panhard rod it there to locate the diff from left to right but also moves the diff sideways as a car is lifted or lowered. You can measure the offset by measuring the distance from the gaurds to the rim on each side and work out if the diff is sitting to one side. Of its only a small amount then i would say it's probably not the issue. Although if it is offset for whatever reason then i would be looking at putting in an adjustable (or standard GQ) panhard rod. It deffinately sorted my vibration out. A driveshaft can still vibrate with sideways offset as well as up and down.

The sidewards angle of the driveshaft amplifies the angle of the front uni.
It also puts angle on the rear uni which usually only compensates for flex in your diff bushes.
I have seen "soft" paj driveshafts where the eyes move out of line whist replacing UJs.
The 60mm bushes are on the later arms, the early arms with 65mm bushes are prone to the bush breaking out of the arm as they have less metal around the bush.
Is your driveshaft too far out of your tailhousing with your lift. Could you do a temporary spacer with flat washers to increase spline engagement into your transfer

Update:

Bought another NJ which had LWB springs in the rear. Put these springs in the old paj which dropped the arse-end by about 20 mm. No improvement at all.

Noteworthy: no vibrations when fanging it in reverse. Makes me think that the u-joint angles are the source of the vibration.

I decided to inspect the rear trans mount more carefully. I noticed the safety hoop inside the mount was very close to the top of the range of movement of the mount, suggesting it has sagged quite a bit. So in went a new mount, and this raised the rear of the transmission about 10 mm (!).

Note that 3.0l rear mounts are completely different to the 3.5l ones.

Anyhow, this has resulted in about 80% percent reduction in vibration! After getting the old mount out, I can see some delamination of the rubber; might have had something to do with it...

So I'm happy - off to the certifier again...

The question is, did the failed mount cause the vibration, or did the vibration cause the failed mount...?