I've been loitering around this list since 1997, and now I finally have a problem/question to ask.

I just recently had my truck (4.6/SC/1999) in for a brake job at a local shop. I asked the guy to check out this recent vibration I am getting (as of about 3 weeks or so ago) as of late. The symptoms are a strong vibration occurring between 2k to 2.5k rpm, which shakes the rearview mirror. My initial thought was a loose exhaust piece, but the mechanic told me it was an internal engine problem and that I should get this taken care of ASAP.

This puts me in a tough situation. The truck is a lease, and the lease ends in October. I was planning on keeping it, all 55k miles of it (the lease only permits 30k), but now I am not so sure.

My question is: what is wrong with my truck? am I the only one? and if it's serious, am I better off trading it in and eating the milage/wear and tear penalty, or getting the motor fixed. I am just a college kid, so finances are non-existant and I would prefer not getting screwed by a local dealership. Any advice would be GREATLY appreciated.

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Matt Watkins
RedClear55@yahoo.com

 

My last truck a 96 sonoma, had the exact same vibration problem. It turned out to be a defective belt tensioner. They tried everything. Alternator, bolts on various parts of the drive train. I'm not saying this is your problem but I know of a quick way to see if it is that or not. Just take the belt off of your truck, and rev it to where you noticed that vibration. If it is internal, then you should hear it yet. If you don't hear it, then you've narrowed the problem down a little. Don't drive anywhere like that however. Did the mechanic give you any indication as to what might be wrong. He must have one hell of a good idea if he says something is wrong inside the motor. Keep us posted.

 

Does it do it in neutral? If not, it's in the drive train.
If it does it all the time, I'd pull the belt and go for a short ride. Be careful as you wont have power steering. If the vibration is gone, it is an acessory making the vibration.

 

Does it do it only when driving or in neutral too.If it does it in neutral to,its the motor or something on it.If it does it only under load,such as when you are driving it is probably a drive line problem.One way to tell is drive it in overdrive or third gear( when ever the vibration occurs) and see if the vibration is the same at the same rpm,then do the same in 2nd gear.If it is the same vibration at the same rpm in different gears,its the motor.If the vibration is noticed at different rpms in different gears,its something in the drive train.

 

Thanks for the input. I tried your suggestions, minus the belt removal.

I just got back from testing the given hypotheses. The most noticable time when the vibration occurs is at interstate speeds, 70+ mph at 2.5k rpm. Tonight, while sitting in the driveway, I revved the motor up to the 2.5 mark, where vibration was barely noticable. I did discover a stronger vibration at 1.3k rpm though, which I have not noticed before. I tried driving it around in different gears, but I couldn't differentiate between the motor vibration or road surface. I guess to describe the vibration is that u can feel it in the accelerator, slightly hear it, and visually see it through the rearview mirror (it causes it to shake).

chuck wheet: the mechanic told me that the vibration was noticable at idle, and that this wasn't the first time he has heard of this. He thought it was pretty serious, and said something in respect to it resulting from a design flaw in the Triton V8s. I have only heard of piston slap being a major concern, causing the replacement of motors, but from what I have read about it, its not what I have.

Thanks again.

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Matt Watkins
RedClear55@yahoo.com