Hey mechanics!


bfletch7441

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I need some help guys, I've got a wicked shake that has developed in my truck. It feels like maybe a motor mount has come loose or busted, but I'm no mechanic. It only happens when I let off the gas and the motor slows to an "idle" when I'm going down the road. If it's shaking and I hit the gas, it goes away. Any ideas?

Ben

BTW-It's an 89 GMC K1500 4x4

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Re: Hey mechanics!

do you feal this in your stearing wheel or the whole car ... your harmoninc dampener could be out of whack ... on that old of a truck it has to be something related to the motor to have it happen at idle ... I would deffinately have it looked at you could trash your whole motor if its the dampener ... Sean300 will be able to give you a better idea wht to look for hes the Chevy mechanic.

Steve

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Re: Hey mechanics!

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Sounds like it could cause the truck to lose control

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Thanks for the concern guy's, but it's not that bad of a shake. I do plan on getting it to the mechanic though. It's our farm truck so I don't drive it very often or very far when I do drive it, but I wanted to have an idea of what was wrong before I dropped it off. Thanks again for the help.

Ben

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Re: Hey mechanics!

Had a Mazda that was constantly having to have the universal joints replaced. Piece of crap.

Sounds just like you are describing.........and would make a LOUD clicking sound when I would turn sharply.

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Re: Hey mechanics!

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Yeah, I go through u-joints pretty regular with this truck, but it's never caused this kind of problem. Those and the carrier bearing seem to the consensus culprit from the shade tree mechanics here at work and everyone on here.

Ben

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Yep the u-joints are for sure the prime culprit. But if you have done this before and the u-joints are wearing out quick. That's a PROBLEM and indicates something else is wrong.

It means either your carrier bearing (or spicer) is most likely bad and it could also mean the spline in the driveshaft is worn out (bad problem). You'd be wise to get them both checked out.

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Re: Hey mechanics!

It's hard to say without me actually driving it and feeling it, but I'd definetly start with getting the U-joints checked. They do go a lot in those trucks, especially if you do quite a bit of off-roading or towing. Could also be the yoke in the driveshaft (part that slides into the back of the transmission). May also be a carrier bearing or pinion bearing. Always start with checking the easiest thing first though, in this case that would be your u-joints. wink.gif

Good luck!

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Re: Hey mechanics!

To check the U-joints properly the driveshaft must be removed. Although sometimes joints can be loose and detected on the vehicle, many times they are seizing up and feel tight when checked in the vehicle. Simply removing 4 bolts and removing the shaft is the better route to checking.

IF you are constantly replacing the same joints I would suspect someone did a poor job somewhere along the line. Often times mechanics like to pound or hammer out U-joints. This gets the job done BUT! More often than not the pounding bends the yoke in so the new joint doesn't fit properly on replacement. After fiddling around long enough the mechanic finally gets the new joint in and the retainer clips in place. However the joint is running too tightly. This creates a couple problems. First the joint may never get proper lube because the cross shaft is tight against the cap not allowing grease to flow through the joint into the cap and lubing the needle bearings properly. Secondly, the cap to cross shaft interference is creating friction which creates heat.

In my shop the technicians are only allowed to press universal joints apart. The clearances are checked and corrected so a free joint is installed. Pounding joints out or in will assuredly result in short usable joint life.

Have a competent technician check the distance between the driveshaft loops and get it into spec. You should have a longer life expectancy of u-joints from now on.

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Re: Hey mechanics!

you might also check the trans mount especially if you hear any noises such as a clunk or pop when you you hit the gas or let off if it is just a vibration I would also sheck the tires for a sign of a broken belt or possibly a thrown wheel weight especially if the tires are larger than factory

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