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Out of balance?

I have a 2000 2500 silverado 4x4, at about 39 - 42 mph it feels as if badly out of balance. I’ve been thru three sets of tires, balanced, "force balanced, and balanced some more, replace drivers sidr hub which was bad, front cv joints, center drive shaft carrier bearing,and inspected u-joints and rear bearing which seem to be fine. can anyone help me out???

Is it an automatic transmission? If so then I’d wonder about torque converter clutch (TCC) shudder. That speed range is the right one for TCC lockup. If you can turn off your overdrive try driving that way for a while to see what happens. (Turning OD off should keep the TCC out of the picture - tho I suppose there might be transmissions where that isn’t true).

Agree with eric c’s post. If that doesn’t prove to be the solution, check steering damper, ball joints, and other suspension fittings, in that order.

Thanx for the info, I’m not sure how to turn off the overdrive, would driving it in low be the same?

If by driving in low you mean “L” then chances are that would disable the lockup. But you’d also likely be redlining by 40 mph.

I don’t know for sure how or whether you can take the lockup out of the picture. It works differently on different transmissions. Some will only do lock up in top gear & in “D.” Some will lock up in any gear over 1st.

There is a trans expert (transman) that comes through from time to time and he would know.

In the meantime if you figure out what transmission you have you might be able to track down its TCC operation specs online. (I think that the trans would be a 4L80E).

One thing you could try regardless is to get it to that speed and as soon as it starts doing whatever it does use your left foot to gently lay on the brake - not enough to actually apply the brakes - just enough to activate the switch. The brake light switch should kick the TCC off. If you have a tachometer, watch that too. It might be fluttering when this happens.

Of course, all of this TCC stuff is still a WAG.

Hey, thanx again. I tried that and no change, Ill try to get it to the right speed where it start to shimy and drop it in neutral,if it stops that will tell me if its in the tranny…?? right??

You may want to take another look at your u-joints. You said they seem to be fine, but the only way to know for sure is to take the driveshafts out and inspect them that way. The rear half of the driveshaft sees the most articulation, and if one or more of the needle bearing cups on that one is frozen, it will be more likely to cause a vibration. Both do need to be thoroughly inspected if this has not yet been done. This sounds like a badly frozen u-joint to me.

I did drop the shaft and the rear cups rotated fine, do you think i should disassemble and check the front? could it be balljoints, or even canter?