vibration on highway

[ocbaud]

I've got a bad pulsating / vibration on the highway around 65-75 (of course)

from what I can tell, its not the tires. it feels like its the whole truck pulsating, doesn't really shake the steering wheel or rattle the truck, but just pulsates. between 65-75 the pulsating gets faster with the increase in speed.

i've rotated the tires from to back and it didn't change at all.

truck is lowered 4.5" front and a flip kit in the rear.


any suggestions for what I can check?

[texastrendz]

two piece, one piece drive shaft? could be carrier bearing, carrier bearing alignment. u joints. pinion angle. balance of tires. bad tires. it took me forever to find my problem, it was the carrier bearing, had to raise it two inches to get the drive line back when i bagged it.

[ocbaud]

once piece

like i said, i suspected the tires, so i rotated them and it didn't change one bit

[SCOTI]

Does it have an OD trans? If so, scrutinize the u-joints & drive shaft balancing.

[ocbaud]

nope
th350

[texastrendz]

if it did not vibrate before, you either have bad pinion angle or the drive shaft is to long.

[ocbaud]

it started doing it really badly after taking it to a safe track environment where i was going about 120mph for a minute or so....

[Brad]

I would say it's the driveline- I'm having the same problem and it's a 1-piece. Mine vibrates bad around 58mph but I can feel it between 40-70mph. I know that mine is about 1" shorter than it should be but I think it wasn't properly balanced when it was built.

[ocbaud]

Originally Posted by Brad

I would say it's the driveline- I'm having the same problem and it's a 1-piece. Mine vibrates bad around 58mph but I can feel it between 40-70mph. I know that mine is about 1" shorter than it should be but I think it wasn't properly balanced when it was built.

that sounds like mine. its very very slightly vibrating at those speeds but doesn't get really noticeable until around 70.

the flip kit is installed correctly but it hasn't been shimmed. any ideas?

[scotts62]

If you want to have it balanced i work at Inland truck in the city just let me know.

[ocbaud]

Originally Posted by scotts62

If you want to have it balanced i work at Inland truck in the city just let me know.

mind shooting me a pm with how much it would be?

[87chevy.com]

you said you rotated the tires, did you have them balanced aswell? Ive had a bad balance job on a custom driveshaft once, it wasnt noticble untill 100+ and when you felt it, it shook the car and by then it already cracked the trans... figured out the trans was cracked after I seen the puddle, removed, welded and reinstalled the 3650 trans. hit 100+ again, and finished the trans for good this time. Went to a different driveshaft shop and they were like this ****s way out... got a new one and had them balance it and all good. See if you have any rust spots on the drive shaft... or maybe something that doesnt have the same ammount of rust... maybe a weight flew off and you will be able to see the "old" mark.
clint

[ocbaud]

alright, so an update

its still doing it, but i found out that it's RPM dependent and not speed dependent.

had it in 2nd gear and at 3500rpm's it started doing it just as bad.

now what?

[87chevy.com]

so, will it do it stationary at those rpms? do you have all of your torque converter bolts installed? maybe one backed out and eventually fell out and you didnt hear/notice it.... that could be more rpm dependant. Do you have any broken fan blades? I broke a fan blade and got lucky it didnt punch a hole in anything... however I didnt know i was missing one it just felt terrible, like i was only running 350ci out of the 454
if it does it at idle within those rpm, remove the tq converter bolts and push the tq converter in the trans and run the same "test" agian... this will let you know if its in the engine or trans..
clint

[66_k10_manny]

I've got something similiar happening on my 66 k-10. Seem to get alot of vibration on the freeway +60mph. But the funny thing is that it's only when im on the throttle. If I take my foot off the gas and coast, it seems to smooth out.

[andrewmp6]

Try taking out the drive shaft rotate it 180 degrees if it changes better or worse then its your drive shaft.

[bedsled71]

find the problem?