Wierd vibration not the drive shaft maybe?

[grandkodiak]

I'm on the highway maybe 1ce every few months, so I rarely get above 70mph anymore. Last year is when I first noticed that above 70 I started to get a really low and loud rumble in any/every gear once above the 70mph mark. I did some research online and posted a few q's and I got the general answer that it was probably that recalled driveshaft causing the vibrations. So I figured i'd get that fixed later on, didnt seem to be such a big deal at the momment.

Now I was on the parkway for a good amount of time the other day and it started to kick in earlier then I remember, around 65. but that isnt the real issue... i started to notice that if i put in the clutch or let off the gas, the vibration went away instantly, even at speeds greater then 65/70. like if i throttled it up to 75 and put the clutch in, the viration would totally disappear. now... doesnt the tranny and driveshaft ALWAYS rotate with the rear wheels? so if it were a driveshaft problem, shouldnt it still be there even if the clutch was down?

also, if i let off the throttle but kept it in gear, the vibrations also severly let off, but i could still hear that it wasnt quite normal, but a major imporovement over steady speed or acceleration.

any ideas people?

ps. yes i had all that work done on my car recently (heads/cam etc) but i was getting this long before all that, even before the 4.10's so, i dont think its directly related... perhaps aggitated, but not the original cause.

[texinteg]

I am having a similar problem. curious to see what other people have to say.

[bigrondownhiller]

how are the tranny and motor mounts?

[joerockhead]

I have a similar problem, but I know for a fact I have a warped right rear wheel.

If it goes away when the Clutch is engaged, then there is a problem in another area. Such was what is stated by the post previous to mine.

[grandkodiak]

honestly i have no idea... my optispark is shot so i guess ill have the mechanic look for the problem when i get that done... but i hopes its not expensive, i just took out a huge loan for school, so all my spending money is pretty much gone for the next 2 years or so

[grandkodiak]

I've been told by a few people and it was even originally speculated by the mech that did all the original work on my car (minus the clutch install) that the flywheel is probably what is causing my vibration problems. now, he said it was probably not cut right or installed poorly, but i had an interesting thought. if the flywheel is imbalanced for some reason or installed poorly, wouldnt the highspeed vibration STILL be present when i put the clutch in?

with that, if it ends up being a flywheel issue, i am going to just flat out replace it, its already been resurfaced, and if its been compromised by this last resurface/recut, then id rather just do away with it. now, do i want to go with steel or aluminum? my cars a daily driver, and i dont do any track racing... but how different is the feel in the clutch between the two? i mean, am i going to stall out when i put the clutch in because there isnt enough weight for the motor to keep up anymore? or does it stick harder/softer? anyone give me a first hand account of what the two feel like?

and what is the weight of the stock fly? i read online 20 but spec told me thier steel is 28lbs, and alum is 14... why would thier replacement steel be that much heavier then stock?

[grandkodiak]

ps what gaskets/fluids/parts will i need for them to change out the flywheel?

[bigrondownhiller]

if it was the flywheel the vibration would be felt without the car even moving. just revving the engine would cause it.

[grandkodiak]

I have no idea now then... it cant be the motor because its only at 65+ mph reguardless of rpm... it goes away when the clutch is engage so it cant be the flywheel, but that means it also cant be the tranny, shaft or rear because they would still be spinning at the same speed when the clutch was engaged.

anyone?

[bigrondownhiller]

then i would check the u-joints.

[grandkodiak]

woulndt they also be rotating with the drive shaft at the same speed?

[bigrondownhiller]

yes, but when you disengage the clutch, the load is from the rear end, not the tranny. i have a tahoe, the rear sags a lot so the pinion angle is off. every year or so i get a vibration. it is the u joints going. if you jack up your car, turn the driveshaft with your hand. see if there is any play. just make sure it is neutral. also while you are there, push up on the rear of the tranny. if it moves then tranny mount is bad.

[grandkodiak]

Sadly I don't have a lift nor would I really know what would be normal conditions under there outside of the obvious with cracks, sheered metal or rust anywho, i'm just tryin to figure this one out... itll be back at the mech probably next week for the opti install once i find out what i need for that in terms of parts, but while its in there hes gunna look it over from engine mounts to fly to clutch to cables to loose bolts backwards and fowards. hes as pissed as i am lol, he did all the work, he wants to be proud of it as much as i

[chevyguy8413]

IN my case , it was a pinion shaft distortion problem...had to replace the diff. pinion...under warranty....rayyyyyyyy

[grandkodiak]

where is the pinion shaft might i ask?

ps anyone have the info on the gaskets/parts needed? all i can guess is 2 waterpump and one main seal?

[2quik6]

Pinion shaft is what is coming out of the rear differiental / pumkin. The drive shaft connects to it, and if the angle is off it can cause a variety of issue, premature u-joint wear, vibrations etc. If you have the stock torque arm on there, it is difficult to get this angle off unless its bent or you've change the ride haight drastically.