Vibrations.... of the bad kind

[apstguy]

See if you guys can help me on this - If I go high way speeds, at a point where I push the accelerator pedel down, the whole truck starts to vibrate. Very bad! It is scary going 75 and the truck starts to shake like it will fall apart and deposit you all over the pavement.

I have ballenced all the wheels, and probably need to get it alligned. My shocks are shot, but I don't think that is it. My greatest fear is it is my transmission It has started to shift "weird" (such a scientific description huh?). The engine and transmission both have 132,000 original miles on it.

At least I know the truck as a whole is solid. My brief encounter with a nasty woman driving an Intergra left me traveling sideways with my brakes locked up on the freeway. I'm still a little bitter.

[79Shortbox]

A friend of mine had a 76 that would make terrible noises cornering, and on the freeway. There was only one loose bolt holding the tranny down to the crossmember. Might check that.

[79BIG10]

Where is the vibration cming from? front, rear, middle? I'm throwing wild ideas out here saying like driveshaft out of balance, bacd motor/tranny mounts, bad body mounts.

[apstguy]

All I hear is a terrible vibration - then the whole truck shutters. It isn't localized in any specific area - feels more like something rotating goes out of whack & sends massive vibrations to everything.

[79BIG10]

Look at your driveshaft to see if the weight may have fell off. Of so take to a driveshaft shop and get rebalanced.

[apstguy]

Now that I think about it, I think a motor mount is bad or joints on the propeller shaft is bad. The truck has been in a crash and one motor mount was replaced, the other wasn't. The joints haven't been replaced probably.... never.

[79BIG10]

Check there I bet that has something to do with it also check everything else to make sure.

[ElGracho]

Hard to say, but my money's on ujoints.

[swervin ervin]

Tyler,

you think maybe you flat spotted the tires while sliding down the freeway? Just a suggestion to add to the pot. Whatever it is, don't keep driving it this way. It's not good for the truck, and it could end up hurting you or someone else.

Also, I want to welcome you to the forum.

[apstguy]

Thank you! I try not to drive it to where it vibrates and shakes. I'll be heading up to the mountains this weekend - I'll try not to abuse it!!!! I'm pretty sure I didn't flat spot it - I was only sliking for about a second - but when you are the person sliding - it seems like 10 minutes! It may be my toasted tire... but that is another story for another board. I'm betting it's the u-joints now too. Helps to talk it out with other people huh? Thanks all for your help!

[bigd65]

BOOOY , that sounds familiar, that is exactly what happened to me on CHRISTMAS morning. only one thing different. the case on my tranny busted. it was blamed on the U-JOINT and for good reason, one of the caps fell off. but when the tranny broke, alot of other things happened and broke also. MIKE is right dont drive it to much, it can hurt you or someone else. if it wernt CHRISTMAS morning there would have been more people on the road during my mis-hap and till this day , i shutter thinking about how nasty it could have been for me and others if they were on the road.

good luck, here is some of things that i have replaced sense the incident:
1.both motor (again) one of them was seperated, i dont know it it was caused by the tranny blowing but replace them they are easy and cheap.
2. the tranny mount, it was also replaced (again) because it was seperated also.
3. the flywheel, if you get the tranny worked on, replace the flywheel, they are only 40.00 bucks for a good one and why not for the peice of mind.
4. the harmonic balancer, that was changed due to a timing problem, but after changing it, it got rid of a vibration i didnt relize was there.

there aot of things that cause vibrations, all you can do is start checking them and replacing them as needed. i still am trying to locate a vibration but hhave not yet, i am thinking my is the carb or timing thing causing it. hopfullt i will find that today.

anyway, i just thought i would share my experience, maybe it will help or give you some other ideas.

[apstguy]

I believe I found the problem - I got to thinking after I talked to you guys so I went under my truck. I started to look where the transmission is mounted and guess what I found? A bolt has managed to back itself about hald an inch from the mount - leaving the transmission to flop around like a fish! I'll replace the transmission mount while I'm at it to make sure it isn't contributing to the problem. There is only two visible bolts holding the transmission to the mount - with one of them not tight at all - you can guess the rest. I'll replace the u-joints too.

[Txstruck]

Originally posted by swervin ervin
Tyler,

you think maybe you flat spotted the tires while sliding down the freeway? Just a suggestion to add to the pot. Whatever it is, don't keep driving it this way. It's not good for the truck, and it could end up hurting you or someone else.

Also, I want to welcome you to the forum.

I agree with Swervin. I have been down that road having locked up my old mini truck go 70mph down the highway and leaving flat spots. Felt like I was driving on square wheels.

[PHOENIX]

One time when I was installing a new clutch I got down under the truck to start unbolting the tranny. I noticed that one of the four bolts had backed itself out a good 1/2" or so. Not a good thought when you find something like that is it

[apstguy]

I crawled under it to tighten the bolt and the other one was hand tight too! The mount is trashed and needs to be replaced. Hopefully, that will fix my problem!

[apstguy]

I went up to the mountains this weekend so I had more time to feel the problem. I traveled 3+ hours in my truck this weekend so I now have a better understanding.

Tightening the tranny bolts didn't help. Seems like a little less vibration now though. It feels like when the truck is at highway speeds, I tap the gas a tiny bit and the point where it downshifts from 4th to 3rd for more power (**Not full throttle - half way**) is when it vibrates. I think it gets on the threash hold of shifting but gets stuck & won't shift, leaving it to vibrate. Luckly, I don't drive on the freeway that much. Think the torque converter might be to blame? (doubt it)

[79BIG10]

Very well might be. Check the TC bolts and the bell housing bolts to be safe.