After reading about 427V8 finding his drive shaft out of alignment and the rear view mirror vibrating I decided to try and find something wrong with mine.
I have a vibration at exactly 62 mph and again at 90. I have a drive on hoist so getting underneith is no problem without a post in the center to obstruct view or the running of a center line string.
On my bigblock the oil pan drain plug is dead center so for the front I tied the string onto the sway bar and run it back centered on the drain plug. For the rear i used the center bolt on the spring assuming this is the center of the rear end.
After tightening the string really tight and making sure it rested on the center of the drain plug and on the center of the spring bolt I eyeballed this in relationship to the drivestrain.
The casting on the transmission lined up perfectly but the drive shaft started off at the front looking good but headed off towards the rear wheel on the passengers side. Looking at it from the rear the bolt under the pinion was about 3/4 in off to the right of the string.
Does this mean the rear end it cocked hard to the right? If I projected the tilt to the right it would probably miss the motor completely. This really puts my drive shaft tilt out of wack. I loosened the front under the pinion but no way can you push the front of the rearend over. I will have to remove the rearend totally , loosen the 4 bolts and make it perpendicular to the rear crossmember and check it again for alignment.
This is what happens when you just bolt things back together without checking :)
The other possiblility is that bolt is not directly under the pinion nut but after I remove the rearend I can check this out.
I would like to hear opinions about this alignment. My vibration starts at 62 is gone by 70 and smooth again until 90 where it starts again. This forced me to drive at 60 or 70 but not inbetween.
Once again see what you started Keith. :cheers:

 

Norval
i would call a frame repair expert and pump them for info.
Can they check this out? Where do they measure?
What is the tolerance limit? etc etc

Maybe you can do "it" yourself with the info. Or maybe it is normal? :crazy:

Also i would raise the tires up by the trailing arm, verify vibrations, take off wheels, try again; but i guess you already tried this :cheers:


[Modified by Matt Gruber, 11:49 AM 8/6/2002]

 

Thank you Matt for the feedback. I have known this car from brand new in 75 . My freind bought it and put it in storage in 1980 and I bought it in 84 with 46,000 miles on it, Original everything. It has never been in an accident even minor. It is totally rust free and restored .
I don't trust most people to work on anything for me. I believe if you want it done right do it yourself. That included everything.
Once I pull the rearend out and if the front bolt is directly under the pinion nut the rearend is installed crocked and I can easily change this. Loosening the 4 mounting bolts, maybe enlarging the holes and then welding a new plate with the refined location welded back in would solve that problem. The play in the holes while tightening them up on the bench might be a problem.
I don't know what a frame shop could tell me about taking measurements but by lying under the car and just looking and thinking, don't this many times you get a feel for what is off and what is needed.
If it was winter the rearend would have been out already but I want to continue driving the car for the next 2 months. The vibration is not felt by the passenger, just me resting my hand on the shifter.
The one at 90 mph is more noticable and I usually pass quickly through the 62 mph one.

 

Er, Norval,
I'm probably barking up the wrong tree here (or just barking mad) but when I changed my trans mount the entire trans moved slightly to one side when I unbolted the original. Luckily I'd marked the exact original position so was able to fight it back into place (not easy). I suspect that maybe I've got a worn engine mount, but could it be that your engine/trans could be skewed slightly in the frame? Probably not - but it's a thought.
:cheers:

 

I think most transmissions are closer to the passengers side of the tunnel then the drivers side. I have repeatedly seen others complain about the interference on the passengers side. I too had to push the transmission tail stock over.
Looking from the back along the string running towards the front the rearend is off on an angle to the right. It doesn't point towards the transmission. .
In order for a pair of universals to work right both the front and rear angles must be the same or one universal speeds up then slows down repeatably every revolution. This causes vibration..
My angles are not equal I am sure. The fix is straighening the rear end out. This does affect the rear tire alignment. Yes the camber will change but this is easily set back. The toe will also change slightly. As the lower camber arms are pulled around they change the setting.
I would just like to know if others have found this out?

 

I'd use one of those laser levels with the attachment on the end to make a long red line instead of a red dot.

 

I have the laser level with the attachment for a line instead of a dot but would find it hard to fix the level on an angle under the car that perfectly catches the 2 reference points. Tying a very strong fine string tightly to the front sway bar and rear bumper making sure they pass throught the 2 refence points was no problem. I doesn't hit anything else other then these 2 points.
I can then lay under there studying why everything isn't in a perfect line.

 

Norval, your car got hit and the frame racked....the engine mounts won't change with relationship to the rear end...IF the frame is square...I can assure you the frame was square from the factory, same as I'd build a wall....
unfortunately with everything on the frame, it's nearly impossible to tell what' where because everything is in the way, things protrude, making strings and tapes bulge and toss the reading off....

it's the same thing as a car crabbing down the road, that sticks out like a sore thumb to me, anyway....most often hit in the pass front fender, and the car has the butt end off to the right...
sounds like what you are looking at on your car...depending on who/what/where/how it can be repaired so you can't tell by looking, not easily anyway...but guaranteed that frame knows....and the mounts and frame and plastic remembers...maybe glossed over, but it remembers..for sure....

I suspect you know this allready...but the engine sits off to the pass side slightaly, about 2 inches or so from centerline...

they had to do it that way to keep the 1/2 shafts the same length...and the pinion location determined that...offset in the case location...

GENE

 

don;t rest your hand on shifter, it will, i repeat, will make a rattle and vibration occur. check the bushing etc and you should solve your problem.

 

mrvette. The car has never been hit. In a previous post I mentioned that I work with the guy who originally bought it and he drove it for 5 years before storing it and then I bought it.
I suspect that the holes in the crossmember are sloppy enough to allow the rear end to be cocked over on an angle if not tightened carefully.
From cutting the hole in the hood for the blower I found out how much the engine is off to one side.
The string is easy to run down my centerline. It touches on only 2 spots. The drain plug which is my reference point and the rear center bolt for the spring. It is totally clear under there.

LT1Driver I tend to rest my hand on the shifter. I know I should not do this but it feels more sporty. The transmission is brand new and so is the yoke so there should be no slop here.


Last night I removed my upper blower pulley and drilled it full of holes then reinstalled. It really cut the blower whine down. I am doing the lower pulley today and upping the boost another 12 %.
Some like the whine of a blower comming down the street but I am getting tired of hearing it. I am certainly not sick of the blower itself but I don't need the whine.

 

I used the same trick to get my tailpiece in line with the driveshaft. I had a vibration that started at 68 and got worse the faster I went. Checked with the string method and found my tailpiece cocked over to the passenger side by 1". Adjusted the rear transmission mount and reduced the vibration significantly. Still have some, I think I may have to have the drive and half shafts balanced.

Norvalwilhelm: Interesting comment about the blower whine. I had toyed with the idea of doing away with the Crossfire intake and putting a blower on, but I don't think I would like a continual whine. My son replaced the chain with a gear drive on his truck and I don't like that sound either. Maybe I'll go another direction.

 

The whine is only the air caught under the cog belt. Drill holes in the pulley to let the air out and the whine should be gone. It was reduced significally last night by drilling the upper pulley. I am drill the lower pulley this morning. My wife has a flat belt and her blower doesn't make a sound and still gets 8 psi anytime.
I will never go back to a normal aspirated motor. Once you are blown you are spoiled for life. The whine can get on your nerves but the brute down low grunt never does.
Listen to 2 850s wide open and the blower, BLOWING and the sound is unbelievable.