i have posted once or twice about a suspicious rattle and/or vibration in my front end. (95 f150 4x4 351 5.8 ifs)... with all the responces it seems to be narrowed down to a susspension issue. i took a look at my system and nothing seemed blatently obvious as to a problem. so i went for a drive and tried to note as much info as possable... with regard to questions from earlier posts.

only vibrates around 115-125kmh
tires recently balanced (problem was there before and still there after)
rattle or vibration is worse going downhill and almost eliminated going uphill
seems as though it is coming from front pass
my vss is still hooped... and my O/D light does not flash

in the case that it is not susspensin related it also seems as though it is throttle related. whether that is do to accel and decel i dont know, but i was also concidering something drivetrain or axle related...

cv
ujoint
driveshaft

all guesses, driveway mechaninc 101...

any and all help is highly appriciated, vibrations make me not drive too fast so that keeps the cops off me but also, everyone hates the guy doing less then the speed limit on the road...

 

well down hill your likely coasting and not accelerating or putting pressure on the drivetrain, so unless your in 4x I can't imagine it being in the front end.

I'd check heat shields on the manifolds and cats for the rattle....the vibe is hard to tell....

 

I believe u-joint problems can vary upon accel/decel....

Can you swap tires and wheels with a buddy, for a diagnostic run? I've come to distrust tire shops and their "balancing acts."

I know what a "vss" is, but what does this mean?

And this?

Have you jacked it up (on JACK STANDS) and wiggled everything, using a bar, where necessary?

Have you tried it at the same rpm it occurs at, but in a lower gear, to rule out a misfire or other engine-related condition?

But we're getting ahead of ourselves--you've gotta do something for us, first:

Please verify whether it is a RATTLE or a VIBRATION.

If it's a rattle: blast your stereo and it will disappear. (Because a rattle is AUDITORY, and a vibration is TACTILE, i.e., perceptible by touch.)

If you still sense it (with the stereo blasting Zepp's Whole Lotta Love) then it's a v-i-b-r-a-t-i-o-n.

We're kinda chasing our tails here, pursuing both at once....

Big Six

Waaaaaaaaaaaaaaay, waaaaaaaaaaaay d-o-w-n...IN-siiiiide....

 

its a vibration. very tactile... ive tried the auto mechanic trick and it works for the noise but i dont have subs to drown out the feel...

vehicle speed sensor... located in/on the rear diff...

dont have a tach so i cannot match the rpm exactly but my with my best guess to rpms i still cannot feel it in a lower gear...

the OD light question was something asked to me by another forum guru and another backyard mechanic, but i think it may have been a brain leak, i also have a problem with rediculously hard shifts occasionaly, mostly switching betwix P-R-D(1st and 2nd and sometimes third gear)...

think thats all of it. i havnt gotten it up on stands yet... but i have gotten under it and poked around... everything seems solid, i just redid all the tie rods and pitman arm and such...

unfortuneatly I'M the buddy with the truck, so none else can share tires...

awaiting your breakthrough...

 

The tranny's shudder at certain rpms once the fluid gets pretty dirty....don't sound like that's it either, though....

 

Hey man,

When I said the following I meant to convey that I know what a "vss" IS...(as well as where it lives).
However, I was asking, what do you mean when you say it's "...still hooped"?

Unfortunately, I don't have any "breakthrough" for you, but if it were my truck, I would have it up on jackstands (when you get the time) because it's impossible to fully check out the suspension with the weight on the wheels--which you already know since you've done some serious work on the suspension already. IOW, things will feel "solid" with 4,000 lbs of truck sitting on them, when they in fact may be quite worn/sloppy.

I have no theories on the trans, as I try to avoid automatics at all costs (no offense).

You could try swapping the wheels front-to-back, to see if this changes anything....

If, after you get it up on stands, if you still can't find anything, perhaps you could pay a shop a 1/2 hr labor to put it up on a lift and run it, at highway speeds, while you/they observe from underneath? Wouldn't hurt to bring a mechanic's stethoscope, either. Needless to say, this is inherently dangerous and should not be attempted by the absent-minded or the inexperienced. Move slowly, wear eye protection, exercise extreme caution and stay away from the moving parts! (Knock on wood three times, too! LOL)

Somehow, you're going to have to either identify a loose/worn part, or eliminate/modify the vibration via a tire swap (front to back, at least?) or duplicate it by running the truck on a lift, IMO.

But wait: I'm still likin' the bad universal joint theory, give that it's different when you're going uphill vs. downhill, as (I believe) u-joints can vary upon accel/decel. Have you thoroughly examined/reefed on all of the u-joints?

Perhaps someone with more u-joint experience can comment?

Good luck with it.

Big Six