Another update, I had my steel driveshaft lengthened one inch......cost my $190 balanced and all, as for my very very little 43-44MPH vibe, it's still there, it's not a big deal, but this is where I stand right now, just some info, my tach is at 2K RPMs and it is only when I'm in 5th gear, when I'm in 4th, 3rd, 6th and any other, it doesn't do it, I still think I have some small adjustment left in the pinion to do, hopefully I can get rid of this little bit that's left over. Any comments???

 

After continued frustration following the instructions provided on the net, I decided to simply revert back to what has always worked for me when I had I had a 4" jacked Jeep wrangler with a 24" long drive shaft and 13 degree u-joint angles. Anyone who has ever been down that road knows the PITA that is to correct.

What I always did on my Jeep was ensure that the tranny output shaft and the pinion were absolutely parallel and to hell what the driveline angles are.

It has alway been my understanding that if both u-joint angles are equal then there can be no vibes due to cancellation. Also if the two angles are equal then the tranny output shaft and the pinion must be parallel. When one u-joint angle is 2 degrees and the other is 4 degrees then its vibration city due to the tranny output shaft and pinion NOT being parallel.

So what I did was toss the angle finder and get out the adjustable bubble level. I placed it on the front of the harmonic balancer and adjusted the the bubble to centered on the dial. Of course we all know that the crank and tranny output shaft must be parallel so this was the easiest place to get the reading from. I then took the bubble level and placed it on the face of the rear end housing where the gear case bolts up. I then simply adjusted the TA till the bubble was centered. The tranny output shaft and the pinion are now absolutely parallel. I also lowered my tranny crossmember 1/4" to account for the lower pinion on the 9". I can lower it a t least another 1/4" once I get longer bolts.

I got the angle finder out to see what the driveline angles were now measuring out at, and they were both sitting on +3 & -3 degrees and the drive shaft was sitting on 0. This is exactly how I set the driveline angles on my Jeep and it never failed then.

I drove the car and 90% of all the vibes were gone, especially the vibe that prevented me from going over 60MPH cause it felt like the car was going to explode. I know that if it ain't dead nuts on right now, then it must be very close. At the very least, it is now drivable.

I then adjusted the pinion both up and down a single degree to try to totally dial it in but it made no difference either way so I locked it down and called it quits.

The Strange chromeoly drive shaft is balanced and the questionable u-joint was replaced so I must assume that the DS is not causing the very minor vibe that I still hear and feel above 60MPH. I am also going to assume that the driveline angle is acceptable as well.

What are the other possibilities that might cause a very minor vibe to remain like this?

 

The only thing left that I can figure on is either the u-joints got shot becuase of the angle being off for any given period of time or my housing output bushing.

 

How do you check and replace the housing bushing?

 

Just take the housing off the end of the tranny, mainly you're looking for any wear on the bushing, if there is none, then you can also check the clearence, but i'm not sure what that is yet.

 

Exactly. Take a look at this document - it's explained and there are pictures

http://4xshaft.com/driveline101.html

The trans output and pinion need to be completely parallel - unless you are running a dual cardan style driveline, then the pinion will be pointed at the trans output.

 

Okay. I am dead certain the remaining vibes are NOT driveline angle. I grabbed hold of the tranny output yoke and there is some up/down left/right slop, at least enough that you can visually see it move. I put the dial indicator and it measures at the very least .020" of slop. Should this thing be rock solid?

Nothing unusual on the slip yoke. Cant see anything unusual on the bushing but it is damn hard to really tell.

If it is the bushing, where do you get one and is it easy to replace?

 

If you are getting a vibration at a certain rpm but only in 1 gear I would say it's harmonics and not the pinion angle.

I've tried many ways to set them up.The best I found was just going by the driveshaft angle to rear angle and forget the tranny angle.I shoot for 0 to -1 degree and that seems to keep all vibrations out.
If you have a vibration at a certain spedd and above like 80mph+.Turn the adjuster nut 1 full turn and see if the MPH changes.If it goes higher you are turning the right direction,lower your going the wrong way.

 

I did that today......earlier today I adjusted my pinion angle up some towards 0 and noticed that my vibe went from around 45MPH in 5th gear to about 40MPH in the same gear.

 

My vibe has nothing to do with RPM. Its all MPH related. I can drive 60 and get the vibes then clutch it so the RPM drops to 1K and the vibe remains.

 

My car did the same thing when I had the poly motor mounts and transmission mount got rid of them and the vibration went away. I would vibrate at 50mph. I've always used poly mount on old school cars and never had problems but this was the first time I had this kind of problem. You should swap them out and see what happens , Iknow its a pain in the ***.

 

I would try changing just the transmission mount to stock first since that is the easiest, and see what happens?

 

I am running all OE rubber mounts. All this started when the DS was tampered with.

 

Ok some more findings here as well.....took a friends stock driveshaft with the same 1350 conversion u-joint (he has a 9" too) and put it in my car and guess what...no more vibes at 40-45MPH at all and the 100+ decel was much much better, the remaining decel vibes I blame on the stock shorter shaft as it was almost 2" out from the flange to the tailhousing......so my conclusion is even though my u-joints feel fine and have no play whatso ever, I've must have slightly damaged one or both of them when my pinion angle and tailhousing angle was way way off for about the first 200 miles of breakin, goes to show ya it doesn't take much to take out a u-joint, I will be getting both new ones and putting them in, hopefully this will relieve me of my issues.

wrd1972-Your angles are right but it seems your numbers are way off......crankcase/trans should be -4, negative being anything pointing down no matter what side the needle is pointing on...as is the same for your pinion with the -4 which is techically a +4, becuase of the fact that your pinion is pointing up....which will give you a 0 driveline angle, which might work out good for you but you might also want to try adjusting your pinion down to a -2. The way you get a 0 driveline angle is the fact that both your tran and your pinion numbers are the same, just one - and one +, trans always being negative (pointing down) and pinion always being positive (pointing up), if you go down in pinion angle it starts to become a - number from where your at now.....if you go up in pinion angle it will be a + number from where your at (which is where you don't want to be). Hope this helps you understand it better, god knows I had a hell of a time triing....

 

Perfect. Your pinion is parallel to the tranny output.

 

Both of those pictures are actually correct, IMO. They are both parallel to each other, which is what you want with a single cardan (u joint) driveshaft.

 

As I might have thought my 100+MPH vibration was gone, it was not.....I was able to find a front u-joint last night and started to replace it, I took the old one off and low and behold there was stress marks on one side of every joint on the thing, put the new one in and took it down the street and my 40-45MPH vibe was even worse, so I put the car down for the night...this morning i decided to go out and adjust my pinion as close to 0 driveline angle as i could, being I was using jacks all the way around, took the car out again and all the way up to 120+ and let off and no more vibrations, as for my 40-45MPH vibe, well thats still there but doesn't seem as bad, I will be changing the rear conversion joint to see if that helps any. I figure anything after that and maybe messing around with the pinion a little more, like 1/2 negative or less, will be common vibes and road noise from the steel driveshaft, TQ arm being mounting to the crossmember and poly mount.

 

Since you found a joint to be questionable, I would go through and replace them all with Spicer joints. What are you looking at, 2 joints? If the one you just replaced wasn't Spicer, I'd replace it again with a Spicer joint.

Then set the pinion/trans exactly parallel to each other.

Then see what you have.

 

Got my DS rebalanced this morning at a different place and found that I was within 4/10 ounce of being dead nuts on. Not bad for guessing on the right size washer and location to weld it. He did pull that washer off and relocate it about 1/2" or so and now the DS is within 1/10 oz of being dead nuts on. I think when it all comes out in the wash, the DS was not as bad off as I thought. Definitely having the tranny crossmember shimmed DOWN 1/4" was complicating the issue as I found from my diagram a few pages upstream.

I am convinced that any other very minor vibes are going to have to be considered normal for the Midwest 9" setup and poly bushings in the suspension or possibly a worn tailshaft bushing.

I think I am going to order the Rockland gear bronze no walk bushing and install it to see if it smooths things out any more. I cant see where it could possibly hurt anything.

 

I was always told to take a measurement at the back of the d-shaft and then the front and split the difference to make them the same and this normally works. I have yet to set my car up so I am not sure this will work but in theory it sounds like it will. This is the method I plan on trying to do first and see what happens.