Hey everyone,

Finally got back into the garage today, weather was just right.

Last year I attempted to install some new UJoints on my Aluminum Driveshaft. What a crapshow. First I tried installing the wrong one on one side, and then I wasn't sure if I liked how "tight" it was on the other.

Well I finally got it back in after deeming it would be OK with the amount of resistance on the transmission side. It wasn't incredibly hard to move, just didn't fall to either side on its own. Might chalk that up to using the "industrial" grade Ujoint.

Anyhow, last year, I temporarily put in my Steel Driveshaft that my car originally had, it drove like crap, and I decided to play with my adjustable torque arm in hopes of fixing it.

Well my first adjustment made it worse, so I attempted to set it back to what it was at.

Fast forward to now.

Put the driveshaft back in tonight, car was seemingly okay, and back to its peppy self, until I got onto the hiway portion of my test drive.
Getting some weird vibration action. Hardly felt comfortable going 70.

So now I am wondering, did I potentially put the driveshaft in wrong. Or is the joint wrong?

Or is it possible the torque arm is still out of spec, and causing some imbalance?

I did also lose a bit of fluid in the transmission taking out and putting in the driveshafts. I was planning on picking up some fluid tomorrow.

Let me know what your ideas are.

Thanks!

 

Factory drive shafts & yokes are PARTICULARLY hard to put U-joints into correctly.

THIMK:

The factory uses those molded plastic grooves to hold U-joints in. They take a random pair of parts, put em in a fixture, shoot em full of plastic, DONE.

They don't machine the inside of the "ears" where the "clips" would fit against. IOW, what YOU think you're aligning to, DOESN'T EXIST.

Ergo, when you replace the U-joints, you have to SOMEHOW get em back in the right place, even though there's NO GUIDE WHATSOEVER as to where that place ACTUALLY IS.

One thing I've found over the last few decades of dealing with this (1st car I had to deal with was my GF's, now YF's, 74 Monte Carlo, in about 1978; I laid up under that damn thing for most of a day before she quit her bitchin) was that it's almost impossible to get it right the 1st time, except by accident. I've had to install U-jointsany number of creative ways to get em centered; tap em each of the 4 possible directions (number em with a paint pen) to seat em farther this way or that, sqweeeeeeeze em with a big C-clamp because the caps were too far apart, and so on. And then, discovering that when I put em together, ONE roller got peeled out of the cap, and ended up between the end of the trunnion and the outside surface of the cap, in which case, NO AMOUNT of external effort, would ever get em to run smooth.

Not to mention, the ears that I've bent and thereby DESTROYED the part. Which, although I've never ruined an aluminum drive shaft this way, but, a heavy-handed approach to removing a plastic-retained U-joint, could easily have DESTROYED the shaft before you got it. Who knows what kind of yutz had it before you. If this shaft is new TO YOU, it might have already been destroyed before you got it, and need more "repair" than a typical driveway or shadetree dabbler like me, can effect.

All I can say is, be REAL PATIENT, and willing to put yourself through trial and error. It's not an un-bolt and re-bolt kind of a repair. If you want it PERFECT (which to me, is the minimum acceptable standard, and I'm not a minimum acceptable kind of person, so "perfect" is just the beginning of getting it "right") you may have to enjoy a few extra iterations before it meets "standards". Then if you can't EVER get it right no matter what, be prepared to take the aluminum part to somebody that can straighten the "ears". Not sure who that would be in your area even though Michigan is a fairly small state. Instinct tells me though, given that state's history, there'll be somebody somewhere somehow that knows how to do it and has the right wherewithal, even though they might be hard to find in a hurry.

Patience grasshopper. Patience is the most important thing sometimes. Which means, realizing up front that it's not just an instant swapout like brake pads or something, you might have to dig a little deeper.

 

So are we to assume my current issue IS in fact caused by the driveshaft?

The axle side was what I would consider properly "floppy" however the transmission side was a LITTLE bit stiff, not overly so, just didn't fall to one side or the other under its own weight.

I will be a tad upset if I somehow got the WRONG ujoint AGAIN. As I have already been through 2 different ones as there really is no clear information as to the proper one needed.

I'm not quite sure I understand what you are referring to by guides however.


Also is there any good source for me to read about the torque arm/pinion angle? Nothing I see seems to explain it consistently, I should have just gotten a regular one, but I was overzealous about getting good parts.

 

Driveshafts have a phase, they can be welded/installed/modified incorrectly even by pro driveshaft shops.



Another thing is the angle of the transmission tailshaft to differential, the angle has to fall within a specific range

They need some angle equal and opposite to prevent vibration and rotate the internal needle bearing if I understand correctly.

Finally they can be out of balance just from poor balancing weights I guess.


One thing I learned after 20 years of this **** is never to modify a driveshaft if you can avoid it completely. Its one of those pieces you don't want to have an issue with. A vibration at highway speeds is NOT fun.

I recommend taking the easy way out: buy a new steel 1 piece driveshaft that fits, and never cut, weld or modify it.

As to the torque arm, if I recall correctly you can measure the angle of the differential to make sure when the trans applies torque to the shaft the angle becomes more straight, or something like that. Its worth looking up and learning how to do all that, heres a thread I found at random maybe it has what you want
https://ls1tech.com/forums/drag-raci...djustment.html

 

Well within driving distance for me, I have a great automotive driveshaft place, I'll bet if the OP searches he can find a similar place in Michigan.......

https://www.ridriveshaft.com/

 

Well, I did the old flip the driveshaft 180 degrees trick. That helped a bit, however the vibe is still there.
I think I am going to try setting the pinion angle again tonight and see what happens.

 

I believe I set my pinion angle correctly, I used this guide.

The transmission side at the yoke on the u joint was reading 4* to the left of zero looking at it from the driver side. It was at about 1* to the left of zero on the driveside at the torque arm.

I adjusted the torque arm side to read 5* left of zero. I believe this is what I was supposed to do.

The vibration seemed better, but something is still amiss.

At higher speeds, mainly around 90, I start getting this bassy vibration in the back of my seat, it's like a *womp womp womp* sound.

Any ideas as to where I should look next? Is it possible it's the ujoint itself? Or should I try flipping the driveshaft 180* again now that the pinion angle is set.

I'm awfully frustrated here!

 

hehe I Know how this one goes

Ofc you want a New driveshaft. After you put the new Dshaft in, and the noise and problem persists, you'll know for sure it was the transmission all along.
Once you rebuild trans and new tailshaft bushings in the transmission, the noise will persist and thats when you'll know it was really the differential.
Once you rebuild the differential and axles and the noise and problem still persists, you'll finally realize it was the tires all along.
Once you change the tires... you'll realize it was the pinion angle all along.
Finally sure about the pinion angle, you'll realize it was the driveshaft all along, both the old and new one are both bad and a third new shaft fixes the problem finally

and also during this period the tires do age and start to whine making it sound like one of the new bearings you recently rebuild is already starting to fail, leading you to dismantle the entire transmission and differential looking for a bad bearing when it was the tires making that sound, everything was fine.

 

So the differential is essentially new, had a trutrac put in last year with a complete rebuild including axle bearings, same gears though.

The driveshaft was fine until I thought it was causing a different MUCH less annoying noise, and I decided to try Ujoints. The driveshaft was an aluminum one out of a thirdgen of a similar year.

The tires are brand new, as of last summer.

I really don't want to buy a new driveshaft, as I still have to put in a new sending unit thanks to another donk up last year.

Im at my wits end. And worse yet?
I lost a socket down the defroster vent, and I can't get it out no matter what I try. Its literally driving me mad. Rattling around.
Mocking me...

BUT other than this, and the countless other issues I'm facing, everything is great. Scouts honor.

 

How is your torque arm bushing? I had vibrations at highway speeds and that was the culprit.

 

When this happens to me, it's almost enough to make me want to open my veins. I've spent a whole day tearing a car apart to get rid of this.

Back to the vibration: have you tried simple things like putting the car up on jack stands UNDER THE AXLE TUBES and having your assistant "drive" it at the speed that causes trouble, and watching it?