1996 burban

I've got 2 questions about a '96 Suburban I bought in CA and brought to MN last year and all responses are appreciated.
My truck vibrates (bad) intermittently between 60 and 70. It'll run for 30
seconds vibrating like nuts and then it'll run smooth for 10 minutes. Speed changes seem to affect it. I've had it aligned, there's nothing loose on the front end that my mechanic or the guys a Tire America (2nd opinion) can find. Tires are balanced. Anyone seen anything like this?
Also when I start it in the cold it makes a rattling, hissing, clicking sound under the truck right in front of the cab. No one can find this one either. Is it possible that the CARB stuff is causing this in the cold weather?
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the vibration sounds like a u-joint to me. not sure on the front end rattle when started cold
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"Mug" wrote: > I've got 2 questions about a '96 Suburban I bought in CA and > brought to MN > last year and all responses are appreciated. > > My truck vibrates (bad) intermittently between 60 and 70. > It'll run for 30 > seconds vibrating like nuts and then it'll run smooth for 10 > minutes. Speed > changes seem to affect it. I've had it aligned, there's > nothing loose on the > front end that my mechanic or the guys a Tire America (2nd > opinion) can > find. Tires are balanced. Anyone seen anything like this? > > Also when I start it in the cold it makes a rattling, hissing, > clicking > sound under the truck right in front of the cab. No one can > find this one > either. Is it possible that the CARB stuff is causing this in > the cold > weather?
On the vibration, is it felt in steering wheel too or not and is it speed sensitive in that when it start to vibrate if you increase speed it will go away and alway happens at one speed or certain speeds too? The reason for the fifty questions is the a driveline/driveshaft imbalance and/or bad uujoints in drive shaft can create some weird vibration senerios like above but I am not sure that is your problem here.
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