Scary Problem, and my own (sad) neglect...

[thesameguy]

Hey guys -

Been a long time since I posted here, but I'm glad to see this place still doing the good work!

I've got an '84 Suburban 2500 with a swapped-in 6.5l (original 6.2l was killed by the original owners). That is probably not important, but that's the score. The truck has 330k on it, but for the last ten years it hasn't been driven much, maybe 2k/yr or so, probably much less - I got it in '06 with 320k on it.

This afternoon while driving I crossed over a highly rutted lane and the truck settled into a violent, rhythmic left-to-right shaking. I seriously thought a wheel was about to fall off. I took my foot off the gas and coasted for a bit, then applied the brakes. The shaking subsided so I pulled off the road to make sure my wheel was still there (half joking!) and then continued on. I didn't expect it was fixed, but there was nothing I could do at the moment. This evening the same thing on the way home, totally different road, not so heavily rutted. This time I recognized the symptoms and paid closer attention - it very much feels like the shaking originates on the passenger side.

When I got home I jacked the passenger side wheel around, messed with the tie road, climbed underneath. I could not find anything steering or suspension related that felt crazy enough to cause the issue. I will jack up the truck over the weekend (not driving it in the interim) to see if maybe it's a wheel bearing, though I don't see how a wheel bearing can only be really bad sometimes. Maybe totally failed shocks? It still has the duals on there from the factory, they are about 12 years old now (knew the original/previous owner so I have a decent history on it).

What I did find, however, is that the passenger side motor mount is obliterated and the loss of height has the outlet of the fuel pump uncomfortably close to the chassis, and there appears to be a resultant leak of fuel - the motor mount is soaked. I started the truck up but could not cause a leak. I'm pretty much indifferent about that result... I'm going to replace the pump just in case - it's old anyway.

So, questions I have for you folks:

1. Anything special to know about replacing the motor mount? I'm assuming jack up the motor, replace - but maybe there's some unforeseen consideration?
2. Same on the fuel pump - I'm assuming while the motor is jacked up, swap the pump?
3. Any guess on what could cause this violent shaking? I don't think it's actually related to the motor mount - if it was engine bay related and *that* violent, there'd be some collateral damage or noise or something.

Any and all help is appreciated. I have a long, long history with this truck (first drove it in '90) and while I use it infrequently, I can't imagine not having it around.

Thanks much!

[CoyleJR]

I can think of several things that could cause your truck to shake.

1. ANY bad steering components. Ball joints, tie rods, idler arm, pitman arm, steering column rag coupling or control arm bushings.
2. Bad or mismatched tires.
3. Cracked frame or loose steering box. Open the hood and have someone turn the steering wheel while you look down at the steering box. If it is loose or the frame is cracked you will be able to see it move.
4. Frozen brake caliber or warped rotors.
5. Bad steering dampening shock if the truck has one. If you do not find any cause and the truck doesn't have a steering dampening shock, installing a shock kit could possibly fix the shake.

I would check the frame first. It is easy to check and a common problem on older Chevy trucks.
Good luck
John

[thesameguy]

Thanks much!

I mentioned the situation to a friend of mine and he immediately said "Sounds like death wobble!" I had never heard of that, but after watching a few youtube videos I'm pretty convinced that is *exactly* what I am experiencing. It doesn't really narrow down the specific cause of the issue, but at least I have some context for it and can provide a better description of the issue!

I'm not sure what my approach is here - I'm really torn between keeping it and replacing it with something newer. I'm trying to balance out sentimentality with fiscal responsibility, and this issue may be the thing that causes me to part ways with a 30 year old, 340,000 mile old truck. I just can't reconcile my heart and my wallet.

I think I am going to park it for a little while and see how I feel in a month or so. If anyone else had any thoughts on addressing death wobble in an old 'burban, I'd love to hear them.

[Yukon6.2]

Hi
It's just a matter of replacing a few parts.
Buy another truck and you will have to replace a few parts on it someday.
If you like the truck for what ever reason,just fix it.You know what you have.
Thomas

[More Power]

The rubber (elastomer) in the passenger side motor mount seems to be the first to fail, but then 320K ain't bad. Fuel will soften and weaken the rubber. Maybe the leak happened first. In any event, yes, replace both the mount and the pump at the same time.

The nuts used with the bolts - that hold the mount to the frame - are a locking variety. They come off hard all the way... Be patient. Jim