Shake caused by wheels?

[Chadwick717]

Hi guys.  I've been chasing a shake in my truck (more of a shake than a vibration) it comes on around 55 then starts to get a little better above 70. It also comes and goes within that range. Sometimes it will be smooth and then start shaking, but most of the time it shakes in that speed range.

Anyway. I put brand new tires on it and got the wheels balanced. I had two separate shops go over the driveline and suspension.  Everything is tight, the u joints look good.  I have a little bit of backlash going to the rear diff but not terrible.  The wheel bearings are tight and don't make any noise that I can tell.  I get no vibration at all under braking, so I've been assuming the front rotors are good.

Could this shaking be caused by a bent or damaged  wheel, even thought I got them balanced?  Any other ideas?  It's not an uncontrollable shaking, but it is really really annoying.

[zieg85]

Put the rear end up on jack stands and see how true everything runs

[Dan75k20]

C or k series ?

[VileZambonie]

Balancing will not take care of a bad wheel. When you had your tires installed it made no difference?

More detail about your truck please. Does it matter what gear range you are in? 3rd, 4th, N?

[Chadwick717]

Sorry guys I know better, shoulda provided more info.  It is a 79 k10 with a 350.  It has a th350 and a np203 with the part time kit installed and manual hubs.  It only vibrates in 3rd gear at highway speeds.  The shaking did seem to get slightly better after the new tires were installed, but the tire shop did say that the wheels were pretty beat up and needed a lot of weights on a couple to balance them out. I took it to a local transmission shop that I trust because I thought the backlash at the rear diff was to much, but after driving it and putting it up on the rack the transmission guy was convinced it was a front end problem and not a driveshaft issue. 

[pholliday1]

Is it more of a shake or wobble?

[Chadwick717]

Hmmmm. I would say more of a shake. The whole hood shakes.

[VileZambonie]

So it only happens in 3rd gear and if you shift into N goes away? What if you lock the hubs? What if you shift the transfercase into 4X4 or low range?

[Chadwick717]

It still shakes with the hubs locked, but with the part time case I'm only driving in hi, not hi loc on the roads, so when I'm in hi loc I'm usually going slow on dirt roads or snow, to slow to feel the vibration.  I'll have to try shifting into N, hadn't thought of that.

[ackland3]

Sounds like your wheels after i wrecked a car i had the same issue but the tire shop had no issue on not telling me!

[Irish_Alley]

does the shaking let off if you let off the gas? also if shifting to "n" shows no improvement you could also remove the rear drive shaft and try it it hi lock, then remove the front and put the rear back in.

[Chadwick717]

Letting of the gas does not help.  If I am going 55/65 mph it shakes no matter what position the throttle is in, although as I said before it is not all the time.

[Chadwick717]

Quick update:  at the shop to get an alignment and my mechanic showed me the printout. The toe and camber are good, but the caster (I think) is negative 2 where it is supposed to be negative 6-8. I think.  There is a shim under the front leaf springs. It is causing this caster.  His suggestion is that the shim should be reversed.  Thoughts? Here is a pic of the shim

[VileZambonie]

Remove it

[Chadwick717]

Remove the shim entirely?  I had that thought as well. He suggested flipping it around, so I wasn't sure.