Vibration in 2WD only! Series II SWB

**jessec96** · 4th June 2020, 06:01 PM

So my SII SWB project is finally at the stage where it has hit the road for the first time in about 20 years for a couple of shake down runs to iron out any bugs. So I took it around the block a few times tonight after work. Found a few small issues which were easily fixed but one that has me stumped is i have a vibration which comes in at around 50kmh under acceleration, feels like it is in the whole car, like rolling over small corrugations. Goes away when accelerator is lifted or clutch is depressed.
The thing that has me scratching my head is it is only present in 2WD. When 4WD is engaged it travels along smoothly with no signs of vibration at all.

Wheel bearings are new. All 4 tyres are brand new and balanced. Front and rear prop shafts have been replaced with new units.

Swivel hubs have not been gone through but seem to be in good order with no movement. Front tie rod ends have a tiny bit of play but i do not feel the vibration in the steering wheel.

Any ideas?

Cheers.

**cjc_td5** · 4th June 2020, 06:20 PM

I'd start with the prop shafts. Take one out and go for a drive, then swap over and go again. Will rule out a dodgy uni joint.

**ian4002000** · 4th June 2020, 06:21 PM

Being a SWB the rear prop shaft is likely to be the area to be looking most. It could be anything form a loose rear fland and handbrake drum or it could be worse and be the angle of the diff. The rear springs can cause the diff angle to change and cause vibrations.
Some people use angled shims under the diff housing to spring to change the diff angle and stop vibrations.

I am sure on the forum there will be info on what to look for and how much angle is allowable.

Ps electronic angle guages are reasonably cheap on Ebay and are needed to measure the driveshaft etc angles correctly.

Ian
Bittern

**jessec96** · 4th June 2020, 07:01 PM

If it were to be diff angle or crook proshafts/unis wouldn’t the vibration be there in 2WD and 4WD?

Prop shafts are brand new and we’re checked over before installing and are in great condition.

Like I said if I engage 4WD there is zero vibration it runs along smooth as butter

**101RRS** · 4th June 2020, 08:17 PM

Do you have free wheeling hubs?

If not, when driving in 2wd the front drive shaft is being driven by the front wheels and rotates with no load so any slop in the propshaft splines can be magnified showing up as vibration. When in 4wd the shaft is loaded up and tends not to wallow around - no vibration.

Of course if you have free wheeling hubs and assuming they are not engaged when you are in 2wd then the front prop shaft is stationary and if you have the vibration then it will not be the propshaft.

But as mentioned - the first place to look is the driveshafts - UJs and splines.

Garry

**jessec96** · 4th June 2020, 08:33 PM

Originally Posted by 101RRS

Do you have free wheeling hubs?

If not, when driving in 2wd the front drive shaft is being driven by the front wheels and rotates with no load so any slop in the propshaft splines can be magnified showing up as vibration. When in 4wd the shaft is loaded up and tends not to wallow around - no vibration.

Of course if you have free wheeling hubs and assuming they are not engaged when you are in 2wd then the front prop shaft is stationary and if you have the vibration then it will not be the propshaft.

But as mentioned - the first place to look is the driveshafts - UJs and splines.

Garry

No free wheeling hubs unfortunately.

Im hearing you when you say check front prop shaft but it is brand new no wear in splines no wear in u joints as everything is brand new out of the box, check on bench before installing and pre greased.

could it possibly be in the front drive shaft u/js?

**Phil B** · 5th June 2020, 05:22 AM

It could be the alignment of the front prop shaft slip joint
The front uj should be offset from the rear. From memory there should be alignment marks on the slip joint

**whitehillbilly64** · 5th June 2020, 05:41 AM

marks.

**Cadas** · 5th June 2020, 07:25 AM

Are the gearbox mounts ok.

In 4wd mode there’s load front and back on the gearbox.

**JDNSW** · 5th June 2020, 08:59 AM

To some extent it depends on what you are referring to as "vibration". My first thought would have been the prop shafts, for the reasons stated above. And one point to double check here is both the security of the bolts holding the prop shafts to the drive flanges (all four of them) and the same for the big nuts that hold the flanges in place.

The other possibility, not so far mentioned, is that it is to do with the yellow knob mechanism. This is in a different position in four wheel drive and also has more spring tension on it. It may be as simple as the tension on this spring or the exact positioning of the fitting on the transmission tunnel that it goes through. Similarly, another possibility is that the anti-vibration spring on the ball of the red knob lever is missing or excessively worn.

A further (slight) possibility is that one of the springs on the transfer case selector shafts is broken and the dog is bumping against its teeth when in two wheel drive. I think this is unlikely if selecting and deselecting four wheel drive seems to work normally.

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