My suburban is shaking help

[rmnkys]

I have been having this problem with my 98 suburban 4x4 (95,000) miles for about a year now. Here goes!
When traveling at high speeds 65 to 75 mph I notice a constant shaking of the vehicle. Here is what as been done in attempt to fix the problem. All tires have been swapped out 2 times,( possible bad tires) brakes have been completely rebuilt front and rear, (found a shoe dragging on the drum) upper and lower control arm bushings have been replaced, ( they were worn out)new shocks all around, (shocks on the vehicle were oem) alignment which included notching the frame to be precise. All of these different things were done at seperate times to prevent unnecessary extra work on the vehicle and the shaking is still there. It seems to go away after I leave the facility and for about a week (maybe just my imagination) but then it starts to shake again at high speeds. I can't pinpoint wether it is the front or rear of the vehicle and neither can anyone I take it to. (obviously because it still shakes). Here are some other things I thought of to check. Motor mounts, transmission mounts, drive shaft out of balance, replace the rims, rear wheel axles bad, harmonic balancer? Does ANYONE have any other suggestions on what to check next? I am tired of putting money into this car and the problem not be solved.

[mrrpm]

Does the shake start around 65 then go away over 75? I've seen bad u-joints or front driveshafts give this kind of problem. Easy to check w/o removing parts!

[rmnkys]

Originally Posted by mrrpm

Does the shake start around 65 then go away over 75? I've seen bad u-joints or front driveshafts give this kind of problem. Easy to check w/o removing parts!

Yes, it does, 65 mph is the magic number. I mainly seem to notice the shaking on long freeway trips. I have checked the u-joints and the had someone else check them and the front drive shaft as well. It all looks good. but how would I know for sure?
Thanks
Kevin

[rmnkys]

I also looked into the distributor shaft issue that was mentioned in other posts. I did notice that the cap was slightly loose but the distributor was tight as can be. I changed the cap and rotor while I was there, maybe this fixed the problem but I doubt it. It sure feels like the shaking is coming from the back end but there is no way to tell.

[mrrpm]

Your problem sounds like a cyclic balance issue. To help pinpoint the shake, ask yourself where do you feel the vibration? In your hands or in your seat? A vibration in the seat would indicate something on the rear of the vehicle. Steering wheel vibration = front of vehicle. Once you figure out where the vibration is coming from, check every rotating part you can think of for wear / out of balance condition, including the wheels themselves (not just tires). Hope this helps!

[sierra0298]

I had the same problem with my 99 GMC Suburban
I had the shake in the "seat" not the wheel. It was bad rear drums. it took us 6 months to figure this problem out. We were buying after market drums. we went to GM dealer and our problem went away.
good luck

Originally Posted by rmnkys

I have been having this problem with my 98 suburban 4x4 (95,000) miles for about a year now. Here goes!
When traveling at high speeds 65 to 75 mph I notice a constant shaking of the vehicle. Here is what as been done in attempt to fix the problem. All tires have been swapped out 2 times,( possible bad tires) brakes have been completely rebuilt front and rear, (found a shoe dragging on the drum) upper and lower control arm bushings have been replaced, ( they were worn out)new shocks all around, (shocks on the vehicle were oem) alignment which included notching the frame to be precise. All of these different things were done at seperate times to prevent unnecessary extra work on the vehicle and the shaking is still there. It seems to go away after I leave the facility and for about a week (maybe just my imagination) but then it starts to shake again at high speeds. I can't pinpoint wether it is the front or rear of the vehicle and neither can anyone I take it to. (obviously because it still shakes). Here are some other things I thought of to check. Motor mounts, transmission mounts, drive shaft out of balance, replace the rims, rear wheel axles bad, harmonic balancer? Does ANYONE have any other suggestions on what to check next? I am tired of putting money into this car and the problem not be solved.