69 350SS VIBRATION

[dutch]

rear end rebuild included all bearings and axles from randy's rig gear and pinion.
motor mounts replaced 3 -times the last with usa made from heartbeat city. all with same results. heartbeat city verified that my frame bracket no's were correct.

i will explore trying to verify my pinion angles .

   Your situation all sounds so very familar to mine that I thought I would jump in here somewhat and I hope it isn't considered a thread hijack - but I have endured the same problem with my '68 Z for many years. I now have all of the bearings / crush sleeve / and parts accumulated now for a rear end rebuild which I hoped would finally cure my vibration after seemingly trying everything else.
    This threat has me worried now if it will in fact end my problems or leave me searching further for answers as you are here in this thread....
    The one thing I always wondered about (thinking if the rebuild didn't cure my vibration) was whether the yoke on the pinion shaft itself could in fact be bent or out of spec slightly and how easy it could be to determine that or if I should just try and get a new one regardless and replace it at the same time as all of the other parts. Does anyone who cares to comment believe that the actual yoke on the pinion could be tweaked by racing (my car was at one point as were many similar cars) and the traction related twisting that occurs with slicks etc.
    I know parts like axles, driveshafts and u joints take most of the beating but I always wondered it the yokes themselves could be damaged by the twisting and shock during racing. I guess because it sits fairly low to the ground there is also a possiblity that it could have been hit on or by something over the years also.
    Is it easy to check one of these yokes out and if so how? Are the 12 bolt versions hard to come by or are they fairly generic? Like most anything else 12 bolt-related, I'm guessing they are probably fairly high $$ items...
    Maybe this could be 'our' answer... - Randy   
 

[tom]

Does the vibration occur at the same rpm range regardless of gear? If so I would be inclined to think Transmission or forward. If it comes and goes at the same speed regardless of gear I would look from the trans back. If it occurs at the same speed regardless of gear, does it happen in neutral (do you have a big enough hill to find out)? I would think drums or rotors if out of balance could cause a vibration as easily as a tire out of balance. Could the output shaft or housing on you trans be tweaked? Is the rear axle correctly aligned relative to the front end?

[dutch]

   My vibration is from the tranny back since if I get it up to speed and slip it into neutral or push in the clutch it is still there and diminishes as the car coasts down in speed. The vibration builds with speed and peaks around 3000 + rpm (approx 60 mph) and is there regardless if the car is accelerating or slowing (usually not a sign of u joint issues).
   I'm inclined to think a bend axle, since I have swapped tires front to back and it persists. Over the years it has ruined my pinion bearing and especially the seal and it now leaks at the pinion so I know I might as well go through the whole unit and change everything once it is opened up.
   That is where my question regarding the yoke came up - whether it could be the cause to shake the end of the driveshaft (which was replaced with new pipe and u joints and balanced) and therefore screw up the pinion seal / bearing because the vibration would be directly focused there...
   I would have tried to get it fixed long ago but for lack of someone I trust to do it that is qualified and that won't charge an arm and a leg to do it, I haven't to this point. Wish I knew enough about setting the lash and pinion depth to do it myself but it sounds like a lot of black magic using the crush sleeve parts and I don't feel confident enough to tackle it.. the yoke is a different story though  - Randy

[Farm Boy]

I had a cyclical vibration above 65 MPH in my ’67 for years. I changed wheels and tires, had the driveshaft balanced, and even replaced the driveshaft but never managed to get rid of the vibration. Nothing I tried got rid of the annoying vibration until last week.

The other day I was at Harbor Freight and picked up a cheap angle finder. When I checked the pinion on the rear end I found it was pointing down 4º. The transmission was also pointing down 3½º. From everything I have read about proper driveline setup these numbers were way off. The way I understand it the transmission and the rear end should be parallel to each other for the U-joints to operate smooth.
 
   

In other words with my transmission pointing down -3½º, the pinion on the rear end should have been pointing up +3½º not down -4º. My pinion angle was way off.

I ordered some 4º leaf spring shims to correct the pinion angle. I actually used two 4º shims on each side. I placed one shim on top of the spring and one facing the other way on the bottom so the shock plate would sit level. I also eliminated the rubber spring pads in the spring perches. I had to add a 3/8 inch thick spacer and a longer bolt to the spring pack so it would fit tight in the perch.

I also made a ½ inch spacer for under the transmission mount to raise the rear of the transmission. My transmission is now 2º down and the pinion is level or 0º. The leaf springs should wrap up a couple of degrees from the axle torque which will hopefully put the pinion 2º up while running down the road.

It’s now smooth as glass.

I am convinced Chevrolet Engineering simply screwed up when they came up with the out-of-phase driveshaft and the incorrect pinion angles in first generation Camaros. I wonder how many first gen Camaros are out there with a high speed driveshaft vibration from an incorect pinion angle.

[dutch]

   I obviously never gave the driveline/pinion angle thing much thought for a street car as I had always heard of it in a drag racing, traction, blown u joints - driveshaft, context - but it may explain a lot. Took a quick gander under the car yesterday and noticed that the pinion has a definite downward angle (how much in degrees I'm not quite sure yet) but downward none the less. Also I changed to stock tranny mount, sub frame bushings, spring eye bushings, and rubber cushions under the spring packs a few years back all because the stock stuff was well worn and or deteriorated. After that I didn't notice that the vibration was much worse although it certainly didn't help to alleviate any of it and now that I think about it, it may have been a bit more pronounced in the higher rpm ranges at that point onward. If anything I just chalked it up to the newer and tighter rubber bits in place making whatever vibration there was, somewhat more more noticeable.
   Regardless, I went out and found a cheap angle finder / protractor unit yesterday, as per the descriptions on the Team camaro site (can I say that here?) and will try and crawl underneath and measure what I find. The shims may be a bit hard to come by around here but it appears that I may end up needing some if what I see is true. I am very anxious to try this out as a possible cure to my problem. My car has always sat up more than many I had seen so maybe that is also something that has also contributed to the problem as it would seem to me that if the angles are off parallel, the sheeper the drivehsaft angle between the output shaft and pinion because the body sits higher, the worse the u joints would bind.
   Thanks everyone for the whole other avenue of thought on this - sure hope it works out! - Randy 


 

[DANW]

incom5633, if you are still out there, you didn't say whether this happened while just in gear or also in neutral too.  If the vibration is only rpm dependent, or also is present at rest in neutral, then it isn't likely that it has anything to do with the drivetrain from the transmission back.