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Oscilating vibration...

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ftn96

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I've got an exceptable oscilating vibration at all speeds above 35. To me its not, but I can drive it and its not too bad. I was wondering what the most likely cause would be. ......
Tire balance or something simple like that?

I have a 4" lift, T-case lowered, good driveshaft, good u-joints, new BFG 33 M/T's.....

Will work for beer, parts and tools.
90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
Tried putting it in neutral and seeing if its still there? I don't think having tires balanced and rotating is ever a BAD idea, but I know there is a checklist (gm service manual?) to check for vibration causes and such. If someone knows the checklist I'm talking baout, and typed it up, would be a good tech article. We probably all will feel at one time or another, a vibration we aren't sure the cause of.



Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
 
My blazer does that. I have a 700r4 and it does it in drive, if I put it in overdrive and back into drive it will go away. I've also noticed it when I rev the motor when the tranny is in park or neutral. I have no idea what it is.

"My blazer may be slow, but it goes faster at higher speeds"

Jim
 
If I get up say like 75 and then put it in neutral, its still there. So thats why I was thinking tires. However, even thought its in neutral the rear drive shaft is still rotating from the rear end, right? SO I wasn't eliminating the idea that for some odd reason Im still going to have to go to a CV shaft on the rear even though its onlya 4" lift.

Will work for beer, parts and tools.
90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
I was just thinking about how its always recommended that the driveshaft be marked when you pull it, in relation to the yoke. Always was told it was for balance. Gonna start rambling here for a sec, not that anyone even asked or suggested it, (yet) sorry.

If the driveshaft relation to the yoke had to do with balance, the driveshaft would be balanced while it was bolted to the transmission and the rear axle. (anyone actually rebalance the shaft after new u-joints are installed?? Makes sense if you think about it) Obviously, the driveshaft is balanced seperately.

If you want to equate this to something, saying the driveshaft must be installed properly would be similar to saying that you must balance the tire of your truck with the axle attached. Obviously no one, even the factory, does this, so thats not true.

I started thinking about "phasing" which I had heard about. If this IHC page is correct, http://www.dorianyeager.com/index2.html
 
Well, there are no weights on the driveshaft. It is brand new. The guy that made it said that when he builds them they are balanced. Maybe, maybe not, but this guy is suppose to be the $hit.

As far as out of phase. I have a one piece driveshaft. So the only thing I could do there, is diconnect the driveshaft and rotate the pinion yoke 1 half turn and try that. However, I doubt that will make any difference.

And the tranny mount is new. It was bad when I got the truck and it maybe has 2000 miles on it. I went ahead and checked it anyway. Its all good.

Will work for beer, parts and tools.
90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
Seems to me that I have always heard that if its above 35mph, that its tires...What happens if you put it in say second and bring it up to high RPM's?


Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
 
It does it in drive over drive and 2nd........., well im not sure. I'll pay more attention next time.

Will work for beer, parts and tools.
90 Jimmy 350TBI-TCI 700R4-241-33" BFGs-10 bolts w/4.10's,
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
At same RPM or same MPH?

Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
 
It vibrates all the time after 40 MPH and up, low RPM high RPM, dont matter. RRRRRRR ..........RRRRRRRRR .........RRRRRRRRRR

Will work for beer, parts and tools.
90 Jimmy 350TBI-TCI 700R4-241-33" BFGs-10 bolts w/4.10's,
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
So that basically eliminates anything forward of the tranny output shaft. Tires are the easy thing. Maybe swapping front to back, if tires are the problem, would let you feel the vibration in teh steering wheel.

Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
 
Phasing has more to do with wear patterns on the u-joints and the true center of the yoke (something about being massed produced and runout tolerance from center). Any ways very simple fix by rotating 180 degrees and trying it. Also, on being the best or $hit on building driveshafts, took mine off this past weekend and took it back to check the balance. Got a call today from a very embarrassed experienced driveshaft builder (wasn't balanced). Mine would start to be noticeable around 65 and got worse as speed increased (new shaft after the 700R4/NP205 conversion). On my other shaft (TH350/NP203), the dust seal at the slip joint was shot and gave vibs at lower speeds. Replaced it and it moved up to higher speeds. Lengthend and rebalanced the shaft, the vibration disappeared.
 
LOL. Well, After I have the tires balanced again, should it not go away, I will be giving mr dave a call.
Thanks for all the help gents. I will be going to a slip yoke Eliminator kit in the future, If it turns out to be the driveshaft, I may just wait till I get the kit installed and the cv shaft.

Will work for beer, parts and tools.
90 Jimmy 350TBI-TCI 700R4-241-33" BFGs-10 bolts w/4.10's,
<A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
 
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