Hey all, so I've been dealing with some issue with the stang, when I am driving around 35-40, 45-50, and 55-60 the car shakes violently when I am either cruising at the speed, or if I get up to that speed and ease off the accelerator before braking. The problem doesn't seem to pop up when accelerating, only when at those certain mph ranges and keeping it at that speed. I took it to a shop and they said that it might be the ignition system possibly misfiring. I let my father drive it for the weekend and he said it was most likely the drivetrain or something in the suspension.

Also, I hear a distinct pop when driving, and it is random, it sounds kind of like I am running over a rock or a bag is being popped, can't figure that one out either.

I had the suspension completely redone in the spring time, and aligned afterward. And these two issues have popped up in the late summer months. My first guess about the cruising speed issue was possibly the carb needing a tune since we had some ridiculous heat waves in California, and I can't seem to reproduce the shaking in the mornings when it is cooler.

What do you guys think?

 

failing U joint.

Replace both front and rear U joints...You can kind of test them by pushing up and down Left and Right on the drive shaft near the u joint to feel for play. They arent very expensive I think you should start there.

 

Well I haven't been able to get under the car and push on them, but I just took the pony out for a ride and put it in park and revved it a little bit, and I could create the same issues that I have while driving. I don't have a tachometer wired, so I can't tell if it is possibly at a certain RPM range. I'll have my shop check out the u-joints when I bring it in, but my guess is back to the ignition system.

 

run the engine at normal driving RPM in park and use the thermal IR noncontact temp gun and check the temps of each exhaust header. They should all be within a 100 deg of eachother. If most are say 550 deg and one is 210 then that one is not firing.

-Gun

 

since it happens in intervals it must be a certain rpm problem, do you have a c4? if so I would say 2500-3000rpm is the problem area.

 

Yes it is using the original c4 auto trans.

 

Good news! Had a new Pertronix Ignitor 2 put in to replace the points and condensers, and the problem went away.

 

cool.........