Nagging Vibration, What Other Shocks Fit Series Trucks

[ArlowCT]

I've had a vibration at around 60mph for a long time no and its starting to drive me crazy. It seems to come in after a few miles or so of highway driving then just will not go away without slowing down or speeding up (above 70mph it gets better).

I have a Ser III 88" running two leaf parabolic front and rear. No freewheeling hubs. 16" rims with BFG all terrains. I have tried 3 sets of tires and two different sets of rims. Both driveshaft’s were replaced but the new front one came clocked wrong and has worn prematurely.

I'm starting to think shocks may be my next thing to check. Could they be starting to fail as they warm up out on the highway? They are about 12 years old. Does anyone know if there are other shocks I can buy that will fit? What other things should I look into?

Any help would be great. Thanks!

[artpeck]

Can you be more specific on the nature of the vibration. Is it feeling like it is mechanical in the drive train or more of a shimmy coming from the tires and front end? Or something else?

[ArlowCT]

It does feel like it’s coming from the back of the truck. I mainly feel it right in the seat, sometimes you feel it in the front end too. The wheel will start shaking and the only way to correct it is to slow down. Sometimes you can see the trans shaking with the cadence. This one has had me real puzzled, almost like it moves around the truck.

[crankin]

What are you running in that thing to get speeds of 70mph?

[LaneRover]

Could it be the driveshaft U-joint o anything like that?

[artpeck]

I asked because back in the day we had an old truck and it was a wheel shimmy that ended up causing a resonant vibration and it would seem to originate any where and travel through the frame and cause the steering wheel to oscillate. Sometimes violently. Slowing down would make it go away. Was ultimately diagnosed as a combination of an out of true wheel on the front end and too much play in the steering joints.

[jac04]

No freewheeling hubs. ... Both driveshaft’s were replaced but the new front one came clocked wrong and has worn prematurely.

If your front driveshaft has excessive wear & you don't have freewheeling hubs, then I would expect vibration at speed. It would also cause the vibration of the transmission you describe.
I suggest removing the front driveshaft to see what happens.

[Boston]

Do the vibes go away or get worse when you accelerate. Also when you lift of? What happens when to put the truck in neutral at those speeds? Have you checked the props half bolts for tightness? Of ok remove the shaft and drive in front.

[SafeAirOne]

I've never known shock absorbers to be the cause of any vibration; They just sit there waiting for something to happen. Nor have I ever known them to 'warm up' after a few minutes of highway driving. They might warm up while driving a rocky trail, or any road in New Hampshire for that matter, but they ought to be doing just about nothing while you're heading down the interstate at lightspeed.

I'd look elsewhere, like driveshafts or wheels or engine.

[giftshopduane]

What about lugnut torque? If your cranking down on the nuts one at a time and over torquing them you could be distorting the rim at point of contact. Bring them up equally then to proper torque specs.. tie rods? alignment? What about swivel ball pins? Bent axle? My guess its in the front end though.. I would travel at those speeds until its fixed though.. if something lets go (it could happen) dangerous.

[TeriAnn]

Shocks dampen the vertical movement of springs. so unless your truck is oscillating up and down your problem is likely steering related or bad U joint / loose prop shaft mounting bolts / bent prop shaft related.

Here's a check list in no particular order:

1. Have tyres balanced and rims check for being true. NOTE: Land Rover wheelsare lug centric and not centre hole centric like most cars. They need to be mounted on a balancing machine by their lug holes and not on a center cone. The centre holes are not exactly in the centre.

2. Check the U joints for wear and the mounting bolts for tightness. If the steering checks out in spec and the wheels are properly balanced and straight, drop the prop shafts and take them to a prop shaft specialist to check to see if they are bent.

3. With the front wheels off the ground check the front wheel for side to side & top to bottom wobble. You could have worn or out of adjustment swivel pins or loose wheel bearings.

4. Check the tie rod ends to make sure they are tight. NOTE: A lot of shops do a free front end steering inspection. They are pretty good at identifying any steering related problems.

5. If steering components are within spec spring for a proper front end alignment. I know most people are caviler about this and do it themselves thinking plus of minus a quarter inch or so is good enough. And maybe they are right if they don't drive a lot of miles and don't go faster than 55 MPH or so. BUT the factory specs for front end alignment is very tight. Tighter than many new cars.

With properly balanced straight wheels. in spec steering components and a proper front end alignment a Series truck is very stable at 75 MPH (I have a 5.0 V8, Ashcroft high ratio transfercase and a proper alignment).

Since someone brought it up, lug nuts should be torqued between 75 and 85 foot pounds.

[ArlowCT]

Very good point on the wheels being lug centric, I was just talking with a coworker about this. I have had my wheels balanced but always mounted by the center hole. I will look into having them rebalanced. At the same time I will make sure they are torqued correctly (don't think they are right now).

Last night I jacked the front of the truck up and let the wheels hang free. I could feel no play in the front driveshaft ujoints and a tiny bit in the slip joint. The swivel pins and bearings are free of slop and play. All the tie rod ends feel good and mounting bolts for the steering box are nice and tight. I do have a steering stabilizer mounted and it is in good shape too.

I don't have my green bible handy, what are the factory specs for alignment? I did notice there is almost no toe in. Should the steering wheel self center when coming out of a turn?

TeriAnn: I agree with you, we have three series trucks (two 88's and a 109) and they are feel rock solid at 75mph (before my truck started shaking so badly that is). But like you said, everything must be in perfect shape.

Thanks for the help, I will try to keep the updates coming.

[I Leak Oil]

Oil on the brake linings can grab and chatter after getting warm as well.

I'm chasing (yet another) driveline vibration down on my truck at the moment as well so I can empathize with you....

[SafeAirOne]

Assuming that you don't have locking hubs, did you remove the front shaft and test drive as recommended earlier? How about the rear? Did anything change vibration-wise during your test drives?

The splines in the driveshaft slip joint splines can wear to the point that they become loose and introduce vibrations when driving at higher speeds. This happened to my front driveshaft. Look for radial play at the slip joint and remove the shaft and test drive (as recommended earlier) to confirm/eliminate this as a cause. Both shafts can suffer from this problem.

[ArlowCT]

Pulled the front driveshaft last night, on the bench it felt very good. Today on the way to work the truck shook just as bad, no better. The shake is very speed dependant, it makes no difference if I'm on the gas, in gear, or in natural. I think it’s time to look at the tires and alignment again!!!!