driveshaft angle

[twanita]

i have been trying to eliminate a vibration when accelerating since my car was new. in reviewing all of the old posts i understand there should be some side-to-side driveshaft angle but it seems like i really have excessive up/down angle when comparing to photos some of you posted. how much up/down alignment is reasonable. do i shim up tailshaft ? see photos.

[Tony Radford]

Jim, have you had a super balance and alignment done on your car? You're drive shaft alignment would have to be pretty wacked to cause severe vibration. Have you confirmed that the driveshaft bolts are all tight? Tire / balance problems are more likely. I recently purchased all new tires and one of the front ones was out of round right from the git go. You need someone who can balance one the car (front) after balancing on the machine.

[twanita]

tony, i am working on the wheel balance issue also. had them done on the car last week but still have shimmy at 50 mph. going back tomorrow.

but this other vibration is different like when accelerating between 10 mph and 30 mph. i look at the driveshaft angle from picture in unique manual and one that phil g posted and my angle looks way steeper. all bolts are tight and no play in tailshft bearing.

[Naumoff]

Your driveshaft angle is a lot. Mine is almost level with the kick to the side.

Is your transmission cross member in upside down?

[Naumoff]

Looking at the photos closer it looks like your differential is higher or at least the yoke is. Is your differential yoke coming out of the middle or is it toward the bottom?

Jim,
Take a wheel off and give us a side shot of your diff.

[eliminator]

You can use a shim if needed, I have seen several cars running a 1/2" shim.

Just make sure the crossmember is in the correct position. I think I have a 1/4" of 3/8" shim on mine. Your angle does look excessive.

[JeepSnake]

Yep - that looks like too much angle. I'd have to dig it up, but the number that just comes to mind is no more than 11 degrees or so on a regular U-joint.

Something else - the U-joint angle on EACH U-joint should be the same. In other words, the plane of the differential input shaft and the plane of the transmission output shaft should be parallel to each other.

When rotational motion is transferred from the trans through an angled U-joint into the driveshaft, you see a change in the angular velocity of the driveshaft: slow, fast, slow, fast, slow, fast, etc. It presents itself as a pulsation that we perceive and describe as a vibration. Passing that pulsing motion through the second U-joint with an opposite and identical angle on the differential input end takes this pulsation/change in angular velocity back out. Thus, you get smooth drive motion at the wheels.

Remember, a universal joint is NOT a "Constant Velocity" joint. But, put two U-joints together, perfectly in phase and perfectly angled to each other, and you have a CV joint.

Shimming to lower the angles and get them closer to identical should get you in good shape.

[twanita]

yes, i have to correct that angle. there is 1.5" difference in height between the 2 yokes. i notice another set of holes in the trans cross mount(see photo) which are 1.5" different. i think that will do it. if i have to change damaged u-joint will driveshaft drop out easily by removing 4 flange bolts or will it interfere with frame?

[Naumoff]

Jim what the H.....!?!

Is the cross member even bolted in? I only have the one hole and it is the one your not using.

It is tight but I can get my drive shaft in and out with out doing anything else. Yours should come out If you have to. Bring it up, over to the driver side and out pass the diff. You might have to take the drive shaft loop apart and adjust for clearance. But I don't see why you can't just jack the trans up and slide the bolts through.

[Aggressor]

I agree with Tony. Get a jack under your tranny and raise it until you can relocate the crossmount bolts in the centered holes. Then check your front slip yoke just to make sure that it still has free movement at the the tailshaft seal area.
I've never seen a Unique crossmount in that dropped position. It appears to be unattached from the position of the bolt. The crossmount bar is always, to my knowledge, centered in the frame mounting tabs. With a drop like that I'd imagine the universals would rattle a bit.


10 minute fix - keep us posted.

- Geary

[twanita]

if you look closely at the center photo you can see a welded sleeve above the crossmount where the bolt passes through. must be for another motor/trans configuration. will move it up and let you know.
p.s. nothing takes me 10 minutes

[Aggressor]

Hey Tony, It must be great to have a drive shaft longer than 6 inches between the universals. To get mine out I've got to press and remove the front universal as it exists in the driveshaft tunnel to get enough rearward clearance to get by the Jaguar flange. (Yeah I've tried twisting the tranny in every direction and angle including loosening the engine mounts and jacking it tight against the top of the tunnel)
It's my own fault for using a 27 inch Toploader instead of the recommended 24.

-Geary

[Naumoff]

Geary,
I have the 6" drive shaft and the long tail shaft on my car. I have a regular yoke and not the flange. I helped Clay change his clutch and he has the flange and I had to pull his out the same way as you do now that I think about it.
Not a bad thing as it keeps you from loosing fluid.

Sorry Jim, you are screwed. It's not to bad to do, but you shouldn't have to pull the drive shaft.
I wonder if where you have it mounted is for a TKO trans.

[eliminator]

On some applications you just jack up the rear of the transmission to get the drive shaft out. Be carefull with the shifter, you can only go so high. There are several cars out there with drive shafts that are just a little too long. A 1/2" makes a big difference.

[brfutbrian]

On some applications you just jack up the rear of the transmission to get the drive shaft out. Be carefull with the shifter, you can only go so high. There are several cars out there with drive shafts that are just a little too long. A 1/2" makes a big difference.

i jack mine till the fiberglass in the tunnel starts to creak, then it comes right out. its not that the driveshaft too long, its just that tight with a longshaft trani. later, brian.

[twanita]

i ended up adding a 3/8" shim between tailshaft and crossmember and it solved the vibration. it made a huge difference in the angle because the driveshaft is so short. was afraid to go higher because of sidepipe brackets on frame.

[Aggressor]

Good to hear about the resolution of your vibration problem.

Let the goodtimes roll !!!!

-Geary