Drivetrain Vibration Questions

rocket dawg

Veteran Member
May 5, 2015
557
Grand Rapids Mi
While chasing my vibration, I did a trans mount. It didnt fix my problem ( tires were my problem) but the mount was 100% shot and needed to be replaced. Fairly easy job, too. Car is a 79 and this was done about 8 years ago.
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
I have minimal balance weights on my 70 Z28 rims with no vibrations at any speeds. I still remember in ‘75 while driving in my 71 Z28 with M22 the speed I started to get vibrations at 150 mph. And that is no sh!t.

That's a pretty good mph with the tires of yesteryear, what gear was in it, 3.73's I would assume with a 26.5" tall tire, if so that's 7,100 rpm @ 150 mph, must of been a rush that's for sure.

I hit 140 mph last time out a few weeks ago, smooth as heck, but only turning 5,200 rpm in 5th, right at the start of the tq peak, so I had the rest of the power band to use, but tires are done, so that was it for me LOL. It was very smooth.
 

COPO

Veteran Member
Lifetime Gold Member
Sep 15, 1999
21,615
Ontario, Canada
^With 3.73, I didn’t have time to look at the tach at that speed, my eyes were peeled on the 2 lane road. But at that speed my ignition shutdown and started again once I let up.

With brand new Firestone F60 Wide Ovals. Cost $67 each in 1975.
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BonzoHansen

Administrator
Lifetime Gold Member
Jun 1, 2005
21,164
Scott from Hamilton, NJ
That's a pretty good mph with the tires of yesteryear, what gear was in it, 3.73's I would assume with a 26.5" tall tire, if so that's 7,100 rpm @ 150 mph, must of been a rush that's for sure.

I hit 140 mph last time out a few weeks ago, smooth as heck, but only turning 5,200 rpm in 5th, right at the start of the tq peak, so I had the rest of the power band to use, but tires are done, so that was it for me LOL. It was very smooth.
I find my car likes to start lifting at 125 or so, the front end starts feeling light
 

biker

Veteran Member
Gold Member
Dec 7, 2014
4,704
Canada
I find my car likes to start lifting at 125 or so, the front end starts feeling light
Lowering the front end a bit seems to eliminate that. Short stiff springs and good shocks stop it from lifting over whoopdy-style road contours that you dont notice at lower speeds. I like to wind mine up to 150+ (briefly) once in a while. The aero at those speeds seems good, my worries now at those speeds are steering play and twitchiness, and tires. Time for a good new box. Tires are new, but not rated for those speeds.
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
I find my car likes to start lifting at 125 or so, the front end starts feeling light

Oh, ok, then I can see that can get a little scary Bonzo.


Lowering the front end a bit seems to eliminate that. Short stiff springs and good shocks stop it from lifting over whoopdy-style road contours that you dont notice at lower speeds. I like to wind mine up to 150+ (briefly) once in a while. The aero at those speeds seems good, my worries now at those speeds are steering play and twitchiness, and tires. Time for a good new box. Tires are new, but not rated for those speeds.

Good points biker, a pair of adjustable shocks can really help out in that area, on both ends. Double even better. I set mine on 8-12 compression and 12-13 rebound, digressive valving as well.



I've got all that lol.

How much toe change on lift vs baseline alignment settings? Added caster helps as well, as well as a good box and pump combo that pulls assist on higher rpms.
 

mallard

Veteran Member
Oct 3, 2013
1,743
SK, Canada
It's been YEARS since I dared take a car up to those kinds of speeds. Driving back to the city from the drag strip one Sunday in '74 I had a little "go" with a Mach 1 mustang on the highway. I had a '69 Grand Prix 428 at the time. From 60 to 100, he had me by about 1.5 car lengths, but from 100 on, I caught up and was about 3/4 car length ahead by 134 mph (this was before metric in Canada) and, like a previous posted said, the car was lifting in the front so I backed off. I've never had a car up to that kind of speed since.
 

BonzoHansen

Administrator
Lifetime Gold Member
Jun 1, 2005
21,164
Scott from Hamilton, NJ
Oh, ok, then I can see that can get a little scary Bonzo.




Good points biker, a pair of adjustable shocks can really help out in that area, on both ends. Double even better. I set mine on 8-12 compression and 12-13 rebound, digressive valving as well.





How much toe change on lift vs baseline alignment settings? Added caster helps as well, as well as a good box and pump combo that pulls assist on higher rpms.

6° caster, toe 0°. I have a decent 12.7:1 3rd gen ws6 16" wheel box, which is ok, better than stock.

I might be able to talk myself into upgrading from the bilsteins. :)

Don't get me wrong, it's not like crazy scary. But I can feel it. Adding the factory front spoiler helped a bit.

I don't really care that much lol
 




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