Alright, time for another update!
Well, after 3 years of trial and error, it looks like I’ve beaten the ‘Death Wobbles’!
Over holidays in January we ventured across to Cann River in the east and as far as Eden on the lower NSW coast. The wobbles plagued our trip and in the end couldn’t go over 80k’s on the journey home. Then still about 160klms from home the lower chassis brace broke from fatigue caused by the wobble and chassis flexing. Now I couldn’t go over 60kph and had to drive most of the way home in the emergency lane. Down but not beaten, I had to fix this problem before the bus goes anywhere again and at any price!
First up was to improve the bracing design and add cross bracing from both directions as well. So now I have top and bottom parallel bracing joined by an ‘X’ in the middle so it is fully triangulated in both directions. There is no way that chassis can flex now.
Next step was to get a replacement panhard bar. Straight away I was on the phone to the USA and ordered a replacement Panhard Bar from WC Motorsports. They claim their bar will fix the wobbles so I was ready to give it a go, it didn’t come cheap at $800, but like I said, “at any price”!
It was a long wait for the bar, I think about 6 weeks, so when it arrived I was on to it straight away. Removing the OEM bar was easy enough, unbolt the chassis end and separate the axle housing end from its ball joint. However the ball joint, which is pressed into the housing, also has to be removed as it is replaced with a different type of joint. I made a jig so that my 5ton bottle jack could press the joint out and put it to work. It took so much effort on the jack lever that I thought the jack would burst a seal and then with a sudden bang it let go.
The OEM ball joint hung down towards the ground from its mounting point in the centre line of the housing while the replacement joint can be used to point up or down depending on the lift and geometry of the vehicle. I had room enough for the joint to go upwards which meant that it would be almost perfectly parallel to the steering arm thus eliminating any bump steer. I also replaced the steering arm (thanks DJR96!) as mine had been deliberately bent to follow the old panhard bar. The new one is straight so the steering rod is now a straight one again. The new bar uses Heim joints each end to eliminate movement but the price is noise and vibration transfer when the vehicle is stationary with the engine running and in drive. Once moving there is no noticeable difference between the OEM bar and the Motorsports bar.
With the bar finished it was back to the caster. The recommendation that comes with the bar is 1.7 caster on the passenger side and between 2.0 and 2.2 on the drivers’ side. So once again it was off with the wheels, coils and shocks. Body and axle housing supported at ride height and set up my measuring jig using a level, builders steel square, welding magnets and all kinds of gadgets! After removing the top bolts which hold the housing to the trailling arms, I rotate the housing to the desired position, note where the hole needs to be then remove the arm, weld up the hole, grind it all flat and then drill a new hole to suit. Then the arm is re-fitted and the process repeated on the other side.
After putting it all back together, double checking bolt tensions and that nothing has been forgotten, it’s time for a test drive.
This is the anxious bit; Until I drive it, I must optimistically assume the problem is fixed. What if I drive it and it’s not fixed? I’d rather live in hope than face the possibility it’s not fixed. What a dilemma!
Good news is it behaved perfectly. There are several places within a few k’s of home that I know will trigger a wobble episode. None of them caused a ripple. That was a week before Easter. Over Easter we went across to Hazlewood Pondage in Gippsland, about 240 k’s from home, and both ways it felt good. I think the wobble has been beaten, finally!
Here is the new bracing
Some shots of the new panhard bar
In the 3rd shot the new steering arm is fitted, if you look closely at the previous 2 pics you can see the bends.
Here's a pic of the jig to remove the ball joint
and the removed ball joint