driveline vibration....PLEASE HELP!!!

[K5DAVID]

Ok so to start off, i have an 88 k5 with a 6" lift, has a 208 t-case with a 2"drop, and of coarse 10bolt axles. i've already had my driveline extened to accommodate the lift. in the beginning, i had a very slight vibration from the driveline, but i had some pretty bad pinion angle, so i shimmed the rearend i got the pinion angle damn near close to "0". however, now that i fixed the pinion angle, the vibration has gotten much worse. i replaced both the u-joints but made no difference.

can anyone explain why the vibration has gotten worse "AFTER" i corrected the pinion angle????

 

[Hogback Fabrication]

Because you didn't correct it in the right way, and really because you need a cv rear driveshaft to eliminate the vibration.

There is some reading on that here.

 

[sweetk30]

almost all blazers with 6" up need the c/v shaft. hate to say it. its the short wheel base.

and the tcase drop is not makin the front like the new tighter c/v angle it has to deal with.

 

[K5DAVID]

ok, i understand that a cv will for sure be better, but i still dont understand how it vibrates more with less angle on it opposed to less vibration with more angle...

 

[sweetk30]

http://www.highangledriveline.com/tech_corner_for_drivelines.html


http://www.pirate4x4.com/tech/billavista/PR-shaft/index.html

under stand this info first to see if it helps you.

 

[Stomis]

A) Ditch the tcase drop. It does nothing but make more issues and is a half ass fix, ESPECIALLY 2 friggin inches.

B) You need an fixed yoke case like a 205 or a SYE'd 241 with a cv rear shaft.

C) Your pinion isnt suppose to be at zero with a standard shaft. Its suppose to be the same angle as the top joint. The pinion only point directly at the shaft when you have a cv at the tcase.

 

[K5DAVID]

A) Ditch the tcase drop. It does nothing but make more issues and is a half ass fix, ESPECIALLY 2 friggin inches.

B) You need an fixed yoke case like a 205 or a SYE'd 241 with a cv rear shaft.

C) Your pinion isnt suppose to be at zero with a standard shaft. Its suppose to be the same angle as the top joint. The pinion only point directly at the shaft when you have a cv at the tcase.

k well, i dont have the money at this time to go out and buy a 205 even if I could find one in my area, i'm just trying to fix this issue cause its my daily right now. I do appreciate your input on the matching angles, that i did not know, i was just told to take the angle out of it and "IT WOULD SOLVE MY PROBLEM" which obviously it did NOT. again thank you

 

[sweetk30]

no problem . you ask her we will help with no name callin .

 

[ryoken]

let me guess, your trying to point the pinion AT the t-case?

that's the prob, your setting it up for a cv.... a non cv shaft has to have the angles the same at both ends... like this...

 

[Hogback Fabrication]

Well, in theory yes what Ryoken posted is right. But notice those 3 degree notations on that drawing, that is what Spicer recommends as a maximum angle on the driveshaft for no noticeable vibration. A Blazer with 6" of lift and a slip yoke t-case is WAY past that.

On a lifted truck there isn't much ryhme or reason to what works best. I honestly had the best luck with mine by pointing the pinion at the t-case even though I didn't have a CV. It wasn't quite vibration free but that was the best for me. Others, however, have the opposite results.

If you don't want to go with a CV my best advice is to play around with the angles and see what works best.

 

[K5DAVID]

ok well then for now im just gonna match the angles the best i can until i can get a cv. i appreciate all your help guys. thank you.

 

[Stomis]

k well, i dont have the money at this time to go out and buy a 205 even if I could find one in my area, i'm just trying to fix this issue cause its my daily right now. I do appreciate your input on the matching angles, that i did not know, i was just told to take the angle out of it and "IT WOULD SOLVE MY PROBLEM" which obviously it did NOT. again thank you

If I was in the shoes of a man with a tight budget I would hack and tap SYE my case for a flange, get a junkyard front shaft and re-tube it into a rear and have it balanced.

Heres the hack and tap flange: http://www.driveshaftsuperstore.com/drive_shaft_SYE.htm

Unfortunately its spendy even for a budget but its much cheaper than trying to find a 241 then do a SYE on it.

The front shaft from the junkyard should be like $20. Plus say $20 for a piece of DOM to lengthen it and it shouldnt cost more than $20 or $30 to have it balanced.

Then your $250 in for not only a fixed vibration issue but a correct fix. And its an upgrade for the truck in general.

 

[ryoken]

Well, in theory yes what Ryoken posted is right. But notice those 3 degree notations on that drawing, that is what Spicer recommends as a maximum angle on the driveshaft for no noticeable vibration.

from my understanding, thats where the operating angle of each joint series comes into play... thus one of the reasons a 1410 is far superior to a 1310.. obviously the beef/strength factor is the primary, but the 1410 also has a far superior operating angle iirc..

 

[Hogback Fabrication]

from my understanding, thats where the operating angle of each joint series comes into play... thus one of the reasons a 1410 is far superior to a 1310.. obviously the beef/strength factor is the primary, but the 1410 also has a far superior operating angle iirc..

A superior MAXIMUM operating angle, yes, no difference with vibes.

 

[K5dreamer]

not to hijack... but for the hack and tap flange... youd need to find a machine shop to do that right? cant imagine thats a do at home with a cordless power drill situation.

 

[ryoken]

A superior MAXIMUM operating angle, yes, no difference with vibes.

right.. but that was my point.... a non cv'd setup with equal bad angles will survive much better with a 1410, whereas a 1310 will be much closer to self-destructing limits.. if your angles are phased within a couple degrees of each other, it shouldn't have vibes, regardless of series..

 

[Stomis]

not to hijack... but for the hack and tap flange... youd need to find a machine shop to do that right? cant imagine thats a do at home with a cordless power drill situation.

No its been said you dont. I've read guys have done it with the case in the car. You need to heat the end of the shaft so you can drill through the hardened outside. I'd imagine a drill with a level on it would be a huge help.

Personally I'd take the output shaft out and do it in a drill press.

 

[Hogback Fabrication]

right.. but that was my point.... a non cv'd setup with equal bad angles will survive much better with a 1410, whereas a 1310 will be much closer to self-destructing limits.. if your angles are phased within a couple degrees of each other, it shouldn't have vibes, regardless of series..

You're right, in theory (certainly the 1410 would be farther from binding).

(Ryoken I know you know this)

The problem is that regular u-joints vibrate, it's part of how they work: each cap speeds up and slows down as the rotate. The idea is to have the u-joints operating at the same angle such that they speed up and slow down at the same rates and the vibrations cancel each other out.

The problem is this really only works at small operating angles (hence the 3 degrees I mentioned before and why you see OEM cv driveshafts on shorter/steeper driveshafts). Once you're trying to cancel out two joints operating at 20 degrees, it may seem like it works on paper but on a truck it often doesn't.

My theory is that, let's say that a shaft with a joint at each end, with equal 3 deg operating angles, can eliminate 95% of the vibration (the angles might not always be perfect due to flex in springs, trans mounts, etc). It seems nearly vibration free.

Now, with the same setup but 20 deg operating angles, the operating angles may match and the two joints may eliminate 95% of the vibration produced but if the vibration produced at 20 degrees of operating angle is 10 times what it was at 3 degrees, you see 10 times the vibration and now it's very noticeable.

My .02

 

[ryoken]

hmmmmm, good point... obviously keeping the operating angle down is optimal..

i've seen it in big powered jetdrives in the boats running jackshafts... i forget what series joints where in em, they where huge, but when i changed the operating angle on the driveline install from 11 (manny said i could run upwards of 13) to 7 degrees, the operating temp of the joint under working conditions dropped from 140 to 105... they certainly wheren't "working" as hard at that point... tho no vibes where present at either angle..