[RA6T7GTO]

hope somebody has a good idea, my 66 lemans develops a wobble at 40 mph, i can see rear view mirror shaking and can feel it in the floor at my feet.i feel it a little at slow speeds but 40mph is where you feel it the most,i changed my wheel and tire combo, had tire rebalanced 2 times already,i put in new springs and shocks in the rear and still no change.front end isnt too bad, one balljoint has a little play but i dont think it would effect the ride,any help would be great, thank you

[jwcfbd]

what trans do you have in it? I had a 4 speed in my Firebird and it had a bad vibration on the highway. I found out that my flywheel was warped.

[RA6T7GTO]

it is a 3 sped saginaw,i put it in neutral and it still does it,if it was a flywheel wouldnt i feel it no matter what ?

[jwcfbd]

I would think so. In my case it was at around 60-70mph. I did forget to mention that my driveshaft was a little off also. When I replace the trans with a 5 speed I also replaced the driveshaft and clutch/flywheel and now all is good. An easy place to start is have your driveshaft checked out.

Any one else have any ideas?

[RA6T7GTO]

the driveshaft is my next move, i only been in florida a short time and dont know where to bring it to have it balanced, thanks

[speed_racer]

mind try asking over at floridajeepers.net , the offroad guys replace driveshafts pretty often, so they can def help you out

[Brett_ty]

I posted this on the street forum..but then I saw this one, and thought I might pile my post on this one as well.



Have noticed that there is a slight vibration when driving the car around 65-75 MPH. It's not really bad or noticable anywhere except feeling and watching my hands on the stearing wheel. Cant really feel it in the floor board or see it in the rear view mirror...but you can see/feel it in the steering wheel for sure.

At first I thought it was just the crappy road conditions around here, but today I took it out on some nice/smooth/newly surfaced roads where I thought it should travel like on glass...and the slight vibration was definatly there still.

New Things done to it this summer:
a) rotors/pads/calipers (front)
b) Drums (rear) (drums were placed on machine to verify round/balance)
c) balanced "Inland Empire" Aluminum Driveline, yoke and u-joints
d) Currie 12 bolt posi rear w/Hotchkis upper/lower control arms
e) Tremec TKO 600 (pinion angle is 4-5 degrees)
f) Centerforce Duel Friction Clutch Kit (flywheel was re-surfaced)

I have gone through so much this summer and it could be anything listed above, so I thought I would trouble shoot the easiest first.

I have read a few guys here that stated to "rotate driveline 180, that will put you back in "phase" if your out of it and vibration will go away" (or something to that affect).

1) Is that simply disconnecting rear driveling u-joint from the rear pinion and rotating it there? (leaving the slip in the transmission)
or
2) Removing the driveline from the car pressing the u-joints out and swapping the slip yoke to the other end (the end that was attached to the rear).

And
What does that mean "driveline out of phase?"

[LPete]

Originally Posted by Brett_ty

I have read a few guys here that stated to "rotate driveline 180, that will put you back in "phase" if your out of it and vibration will go away" (or something to that affect).

1) Is that simply disconnecting rear driveling u-joint from the rear pinion and rotating it there? (leaving the slip in the transmission)
or
2) Removing the driveline from the car pressing the u-joints out and swapping the slip yoke to the other end (the end that was attached to the rear).

And
What does that mean "driveline out of phase?"

#1 is correct. The driveshaft and pinion flange are marked at the factory, and when the driveshaft is installed correctly the heavy spot on the pinion/pinion flange ends up 180 degrees from the heavy spot on the driveshaft, canceling slight out-of-balance vibration. It may help to rotate the driveshaft in the pinion flange to see what happens.

Out-of-phase is different:
Simple U-joints cause the driveshaft to accelerate and decelerate slightly with every revolution. U-joints are "in phase" if they're installed so the crosses in both joints are in the same plane, canceling out the acceleration/deceleration (which can cause vibration). The only way they can be out of phase normally is if there's a slip yoke in the middle of the driveshaft that can be assembled with the joints out of phase (the yokes not in the same plane). I suppose a yoke could be welded on the driveshaft tube out of phase, but that doesn't seem likely. Rotating the driveshaft in the pinion flange doesn't change u-joint phase.

Here's a website that explains this: http://www.4crawler.com/4x4/CheapTri....shtml#Phasing

[Brett_ty]

[QUOTE=LPete]#1 is correct. The driveshaft and pinion flange are marked at the factory, and when the driveshaft is installed correctly the heavy spot on the pinion/pinion flange ends up 180 degrees from the heavy spot on the driveshaft, canceling slight out-of-balance vibration. It may help to rotate the driveshaft in the pinion flange to see what happens.


Thanks
one more question, so since both the rear and the driveshaft are new (currie/Inland Empire) and from diff. companys, supppose I had it installed correctly, I am guessing that if I do the 180 swap I should get a wicked vibration.
There is an aluminum weight that is welded on the driveshaft towards the pinion end (I suppose that it was from balancing)..So I am guessing that is the "heavy spot." How can you tell on the currie rear pinion flange...what am I looking for there to indicate the "heavy end?"
Thanks again

[pngoat]

The problem could still be the fly wheel. I had the same problem with my 65 goat. I had a bad vibration between 40-50 mph. (1600-2200 rpm). In my case it turned out to be the fly wheel. Below 1600 rpm and above 2200 rpm things were fine. Between 1600-2200 rpm it would shake your teeth out. Do this. With the car in neutral and stationary slowly rev up engine and see if you feel the vibration. If you do then the problem is an engine balance problem. The machine shop that balanced my fly wheel said it was "way out". Once it was balanced the engine ran smooth as silk. If the fly wheel is out of balance you will only feel it between a certain rpm range and not from idle to red line as is commonly thought. Why this is I don't know. I am not an engineer. I just recall reading this on other threads. If it is the fly wheel it's best to get it taken care of as you can wipe the main bearings or, in the worst case, break the crank shaft. Hope this helps. Good luck.

[jjscerbo]

What were your Caster readings when you had the car aligned?

These car are notorious for not allowing enough caster. The frames have tendency to spread over time. You may need to install offset upper control arm shafts.

Joe