For those of you who have followed my changes over the years (I won't say the word "progress"), where did I pick up my vibration which I have narrowed down to pinion angle. I am guessing when I dropped the car for a lower stance, i made it bad, and Cal-tracs preloaded 1/4 turn made it a little worse. Anything else? Which way should I shim the rear to correct it? Opposite direction of the Cal-trac preload sounds correct, but I have no experience in these matters. I bought 2-degree shims, and need to figure out what all has happened to the engine-trans angle, as well as the rearend angle, and which way I need to shim it to correct it.
Scott,Did you check the pinion angle before you added the caltracs??Even with em you should have 3 to 4 deg downward angle on the pinion at rest(ride height) if you have less than that try adjusting your caltracs to correct it before you shim.You are sure all else is correct and in proper working order?? U-joints are good,drive shaft is proper length,balanced properly ETC... Good luck hope this helps you out.
To start you will need to know what angle your pinion truly is. I have saw them be from 8 degrees positive to 8 degrees negative. Anything more than 4 degrees negative makes mine vibrate. But each car is different. You will also need a tool simular to this. http://www.sears.com/shc/s/p_10153_12605_00999793000P Hope this helps.
I have the Sears magnetic protractor, and as far as I can tell, I am around 2-3 degrees at both ends. I have a horrible vibration, but if I unload the caltracs, it almost completely goes away. I have replaced the tailshaft housing, bushings, and seals, new motor mounts and trans mounts, completely rebuilt rearend last month, driveshaft was balanced and straightened month before with new u-joints, etc. All within the past 100 miles or so. Also new rear springs, bushings, and shackles. About the only thing that hasn't been replaced is the upper ball joints on the front, but it vibrates even on jackstands with the front on the ground. I have taken the car up onto jack stands under the axle and run it to see where the vibration kicks in, then removed the wheels, run it, and then removed the drums, and it still vibrates around 45 mph. It is not engine, since it did it on the old motor also, and will do it in 3rd gear at low rpms or 1st gear at high rpms, but not low rpms in 1st or 2nd gear below 45 mph. It almost goes away if I take off all preload on the caltracs, so it sounds more and more like pinion angle. More preload makes more vibration. So I was thinking about shimming it up in the opposite direction of the preload and then preloading it again, and trying it out. No, I never measured the pinion angle before the caltracs. It was fine then, and I never bought the protractor until after I got the "wobbles".
2-3 + or 2-3-? Almost sounds to me like a drive shaft vibe. Was the shaft balanced? Is the shaft in time? What about the u bolts on the rear joint, I have saw these being overtightened many times, Which will case the bearings to bind. Are you running the hard trans mount? I cannot run one of these due to vibration.
Ditto, look at the U joint alignment, they should be lined up with each other, if not they'll vibrate. I've got a slight vibe in mine too, fixed all the imperfections, but still got a slight vibe that won't go away. Ideally the pinion should point down slightly so it'll rotate up to align with the trans tail under accelleration. I tried it that way on mine, but the vibes said no way. Installed shims to center the angle & that took out most of the remaining vibes.
I just took the shaft in a little over a month ago. They ran it true and balanced it, and put on new u-joints. I have not rotated it 180, guess I will do that first. Then double check the u-joint bolts. Be nice to find it is something easy like that. After it was balanced, I just disregarded all that stuff thinking it was solved. It actually DID fix a bit of the vibration. I used to vibrate down to 30 mph, now only 50-55 and up. I don't remember what the angles were last time I looked at them. They were pretty close, and in the correct directions, so I started to look at all these other items. Trans mount is direct stock replacement. Think it had a soft top and hard bottom?
I helped a friend with a Mustang replaced a 6 cyl 3 spd. with a 5.0 5 spd. We chaced a vibration for months.Had the driveshaft checked and balanced was perfect according to their machine.Vibration changed but not cured.Changed driveshaft ,vibration is gone. A lot of shops can not spin driveshaft as fast as we do under driving conditions for balancing. Good luck
dont forget the rear transmission mount also. my old one had worn slightly offline and cause all kinds of vibration. when i put in the new one the vibration disappeared. also make sure the rear end adjustment isnt throwing your line off. any left right change in the line from trans to rear can cause vibration (up down should be fine to a certain amount since that is how the travel is designed).
How about a 1/2" drop block under one spring, not the other? I did that a couple years back to correct a lean. It seems like it would be essentially twisting the frame around, and not moving the pinion anywhere. God point on the shaft...I have access to other shafts if I need to test them out.
make any progress on this vibration? Mine vibrates mostly when decelerating from 70 mph. My driveshaft may be short. With the AOD it seems the 90 something Mustang driveshaft is a perfect fit. May opt for the Ford Racing aluminum driveshaft.
Mine does the same thing. Only it's not as bad as it once was. Only a slight vibe on decelleration. I've learned to live with it. It dosn't get driven much anyway.
