Now that I have my catastropic failure addressed, another thing I
noticed on my recent trip is that at about 70mph, I start getting a
vibration, it's a very slow one compared to speed. Kind of a whump
every second or two, on and off. Doesn't go away completely in
between but kind of winds up more every other second or so. It's not
a horrible truck is gonna fall apart one, but it was enough to keep me
below 70. Last time I did any highway driving over 70 was a few
months ago and definitely didn't have it then. Truck is an 89 K3500
454 th400.

Thanks in advance,
Ed

"89GMC" <dziarcak (AT) gmail (DOT) com> wrote

Sounds like maybe a steel belt shifted in a tire.

Brian

At 70mph, a shifted steel belt in the tire is going to show up as more than
vibrating every second or two. Can you hear or feel which part of the
vehicle it seems to be coming from?

On Sun, 18 Mar 2007 06:03:39 GMT, "Augustus" <no_one (AT) nowhere (DOT) net>
wrote:


Remove driveshaft and have it balanced if ujoints check out okay. The
reason it cycles is that he is getting a harmonic vibration and it
sound like it is starting in driveshaft.
-----------------
TheSnoMan.com

"89GMC" <dziarcak (AT) gmail (DOT) com> wrote


Do you feel the vibration under your feet? Under your ass? In your hands? Do
you feel it only at 70+ mph? Have you tried to duplicate in different gears?
Trying to determine if it is rpm sensitive or just MPH sensitive.

"SnoMan" <admin (AT) snoman (DOT) com> wrote

Perhaps if the u joints are okay he could put a worm clamp on the shaft and
try moving it around to see what happens before he goes to the aggrevation
and expense of pulling the shaft and sending it out.

Or perhaps he should check his motor and transmission mounts first.

But hell, I'm sorry what do I know? I'm just a troll.

On Sun, 18 Mar 2007 09:43:19 -0400, "Roy" <Roy (AT) home (DOT) net> wrote:


Well you are a troll sometimes by some of your very actions but your
idea has some merit but experiance has taught me the GM driveshafts
are rarely balanced well from factory and as they age, flex and rust
they tend to go out of balance even more and make their imbalance
known if way such as this. One way to give more insite as to whether
it is a balance problem is to place vehicle in neutral at that speed
and if it is a balance issue it will not change it much at all. It is
does change a lot it may be ujoints. If it was motor mounts it would
show itself at speeds other than this and be of different nature.
-----------------
TheSnoMan.com

On Sun, 18 Mar 2007 12:11:29 -0500, Heatwave
<M3LT1NG5N0WM3N (AT) WAH00 (DOT) COM> wrote:


You mean the H with logic right? Nothing I said was bad advise here
but you would have the original poster chasing his tail if it was up
to you.
-----------------
TheSnoMan.com

Per SnoMan:
Which begs a question that's been in the back of my mind for awhile: will it
damage a GM automatic transmission (4L60) to put it in neutral while the vehicle
is moving.

Might sound like an inane question, but I'm pretty sure that somewhere I read an
instruction manual that cautioned against putting the transmission in question
into neutral while the vehicle was under way.
--
PeteCresswell

In article <etjfm10av7 (AT) news1 (DOT) newsguy.com>, Roy (AT) home (DOT) net says...
Yeah Roy you aren't diagnosing anything correctly if you aren't jumping
in there and throwing someone elses money away. To hell with questions
or basic diagnostics! Spend money first!