Shaking at high speed

#1
Hi all, I have a pretty bad steering wheel shake at 95 kmh and above, and have tried lots of things to sort it out. Wheels and tires are new and blalanced, had bearings checked and tightened, put on new tie rod ends, had a wheel alignment, and backed of the brakes because they were rubbing a bit before ( a scraping sound once every revolution on the left hand side). Still no luck. I THINK the shaking continues at high speed downhill when I depress the clutch, but a bit hard to tell without a decent highway hill. I cant drive through the vibration, it persists up to redline. I also have one slight crack developing in engine mount. Its a 1993 Isuzu NPS. Body removed for kids at the moment and have a tray on. Would live some suggestions, I'm getting demoralised!
 

SkiFreak

Expedition Leader
#2
I realise that you said the tyres are balanced, but have you tried swapping front for rear to see if there is any notable difference?
 
#4
What type of wheels do you have (original or singles).
I had a similar problem a long time ago with shake at higher speeds.
Ended up being my super single with a 12mm centre was deforming the brake drum.
Removed the wheel and brake drum then took the wheels in with the hubs, and had the drums shaved to match the wheel while bolted together. Each front wheel only belongs on that corner and only matching that position on the drum.
Never vibrated again, and never needs balancing either
 

BradK

New member
#6
You can put the back axle on stands and then drive the truck up through the gear. You will then be able to see if it is driveline related. Just make sure it is securely supported and chocked!

Just as an aside my brother had new tyres fitted years ago and even though the tyres balanced correctly and where not out of round they vibrated quite badly. Turned out that the tyres had a manufacturing defect where the tread grooves were not molded straight on the tyre.
 
#8
Thanks for all the suggestions, I have swapped front for back and will see tomorrow if that makes a difference. The driveshaft seems OK, everything is tight when I try to shake it underneath? I think the next step is an "on truck" wheel balance, maybe my hubs are out of whack... I recently changed over to super singles. Could it be out of round hubs maybe?
 
#10
Try to find a shop that has an old on-the-car wheel balancer. Balance the entire assembly together.
The story about the 12mm super single centers has me worried as I just started running those w/ Hankook 37 x 12.50 x 17's.
.....After reading all the stories, I decided to use ceramic beads @ 8ozs per tire. Results have been acceptable with only a slightly discernible dynamic wobble
after fairly dramatic speed changes or when the beads are "hunting" for their spot when accelerating. I think that next time I will try 10 oz's per tire.
A clamp on, gooseneck disc brake runout meter ($100ish) can be an invaluable tool in hunting down wobbly parts.
 
#11
if your still running the stock rims ill bet its a dodgy rim
had the same issue on mine, rotated through to find which one then used it as the spare
then replaced them for signles
 
#12
Odd as it may sound have had similar problems with old Inters and Leylands where we had to get hubs and drums balanced seperatly then on vehicle wheel balance 35 years ago but tried several new drums before we found one that was acceptable as the vehicle was under warranty the dealer was trying to increase the number of his trucks in our fleet and was happy to work with us to solve the problem good luck
 
#13
How have you been with your tyres? I can tell a number of truths with regards to a number of the higher weight rated tyres as told by the importer. Chances are it's the tyres.
 
#14
I had the same problem. Brand new tires were square. They balanced ok, but if you jacked the axle up off the ground and spun the tire you could see a couple of them were nearly 3/4 inch out of round.

Allan
 
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