Low speed vibrations! Even with the new shaft!

[porkchop]

I am getting tired of this t-case/driveshaft thing. Well I got my shaft back today and it looks great! Ggot home and hooked it up fit perfect. Well I take the wag out for a test and as soon as I start off I get some serious vibrations. The same ones that I was feeling when I first drove it back from work before I had the shaft shortened and the t-case was tore down and cleaned. The vibs are real bad at slow speed and then they smooth out at about 2000 rpms and then they start to show back up again but not as bad.

Here is the run down, new rear shaft to include u-joints, front shaft not installed. T-case has been broke down cleaned and inspected.

My thoughts are:
1) When the t-case gear went it took the rear pinion with it
2) There is a bad bearing on the rear output of the t-case
3) The driveshaft angle is causing it

I am hoping that maybe you experts might have the answer I am looking for. I am so tired of this problem. I miss my Jeep!

[Jeep Craze]

Hey just a question probally answered before but you said around 2000 rpm it does it. Does it do it in park? or (N) reason being is I had a chevy 305 motor do the same thing turned out to be the balancer. Just a thought Craig

[porkchop]

Sorry let me clarify that. It does it when driving at 2000 rpms. Am not real sure of the speed since my speedo broke while driving it home from work after the temp fix.

[WINGO]

As you probably know, I will be installing a D 300 in my '84 that will include an axle swap and an SOA to pick up the necesary clearance for the front drive shaft to the 727 trans.

I am considering purchasing the Rubicon Anti-wrap spring perch and read this product evaluation:
Rubicon (http://www.off-road.com/jeep/reviews/rubexpress.htm)

There where some comments about drive vibration that you could find helpfull.

[mark]

pc
does your rear shaft have a cv on the tranfercase end?i had a vibration and very short u joint life till i spent the bucks(400)for a cv rear shaft.i will be sellin mine soon because im going to larger u joints.

[porkchop]

No CV :( . I read somewhere that the angles are suppose to be the same at the axle and the t-case, is this true? I had a Magazine with a lot of good info in it but is out in the garage in a stack of them and can't remember which one it is.

[64Trvlr]

The angles of the transfer case and axle should be within 1 degree or so of each other. That will really help things out. When they did the shaft did they balance it?
:cool:

[mark]

the angles should be the same up to a point.with too much lift and a severe angle the only solution will be a cv shaft.been there done that.

[porkchop]

64, I had them balance it too. This week end I am going to turn the blocks in the back around and see if that helps me at all. That will change the angle to what I should need. First I am going to measure the angles at both ends to see were I am sitting. I am pretty sure it is from the angle.

Mark, what is the center to center length of the rear CV you are running?

[scotty]

assuming that a competent shop installed the ends of your shaft in phase,and that the shaft is indeed balanced,you might try flipping the driveshaft 180* from wher it is. manuals always tell you to mark the yokes for shaft reinstallment. in most vehicles it doenst really seem to matter how i put the shaft back in,however,1 instance with my 62 falcon produced a very,very bad low speed vibe.my dad reinstalled it 180*,and the vibes went away. its maybe worth a shot anyway.

as for a bad output bearing,pinion or pinion bearing, can you grab either and wobble it around? is either leaking? is it making any other noises? i doubt that either of these is your prollem.

if that doesnt help,id prolly take the shaft to a different shop and have it checked.as j20 pointed out in the other thread,there are lost of factors that need to be taken care of to make it right,not as simple as just cutting the tube and rewelding.

[River Beast]

Bryant,

Yes....yoke angles should be within 1-2 degrees to cancel any vibrations...like this...
http://www.4xshaft.com/images/2joint_angle.gif

the CV setup will cancel out the vibes... shoudl look like this:
http://www.4xshaft.com/images/cv_angle.gif

This info is from Tom Wood's Custom shafts (http://www.4xshaft.com)

good info there.

[porkchop]

Thanks for the link, Todd! That's the info I was searching for.

[miked]

keep in mind that the angle of the xfer case output should be within 2-3 degrees of the pinion angle - but not exactly equal. apparently you want some offset for harmonic purposes.

you can use a simple magnetic angle protractor, Sears had one for $9 that I bought that did the trick for me. www.craftsman.com, (http://www.craftsman.com,) item #00939840000.
http://www.sears.com/data/product_images/tools/standard/00939840000-dv.jpg

the angle off the xfer case is usually around 4* down, YMMV

note that with the CV driveline you want the pinion angle to be inline with the driveshaft. on rigs with alot of lift this may cause the rearend to be angled up so much that you bind up the attachement for the shocks and the shock tubes start to ride against the axle tubes -- that and so much shimming is req'd that the pins from the spring pack don't go all the way thru to the sping perch pads to hold the axle down.

how do I know this?? ...don't ask

[Iron Horse]

I picked up one of those protractors....works nice. Good price too.

Thanks for the link Todd...I too was looking for that info.

[porkchop]

I already have one of those protractors at home. It has served me well in the past.

Miked why can't we ask ;)

[TexasJ10]

I'm not a master mechanic, but I am pretty good at making mistakes. I have had a similar problem twice in the past. Once it was caused by my failure to properly seat the u-joint into the yoke, and the second was because I ignored the instructions about marking the drive shaft and yoke and promptly reinstalled the drive shaft out of phase. Fortunately neither were difficult to fix. Unfortunatly it takes a lot more time when I have to do stuff over.

[River Beast]

Glad I could help out... :D