72 Mercury Comet GT in Germany

the only 3 things that i have ever found that a differential to be causing vibration are, off center yoke, pinion bearings so loose that they dont hold the yoke on center, and the pinion angle being wrong.
did you find anything on your rebuild of your rear end?
have you checked what your pinion angel is in reference to the engine/trans angle?
on the mustang, did you use the proper size u joint for the maverick yoke. most maverick yokes use a big bearing 1310 ujoint and mustangs usually used the standard 1310 ujoint.

 

on the comet, i found absolutely no preload on the pinion at all and was actually able to slide the pinion in and out a little. now it has the proper preload. it was my first time working with a crush sleeve, and i naturally tightened it too much the first try. i was lucky to have another one at hand. as i already had a good dial indicator from rebuilding my steering box, i did not find the whole task too difficult.
i had checked pinion angle before and corrected that by using angle shims on the axle.

i haven't dug into the mustang as of yet, but i'm aware of the small cap/big cap aka 1 1/8 vs 1 1/16 issue on the u-joint and have used the correct one.
it's vibrating, too, and i believe - as it's a much lighter convertible - it's reacting to that.
as both differentials have been done by the same place i suspect the pinion on that one to be faulty, too.

 

sounds like your on the right path. i always like hearing of how you just go out and drive 120mph. here if you get pulled over going over 100 its considered driving with intent to kill. the only legal opportunities for us to go above the max speed limit (80 is the highest i know of in this country) is in organized racing. the open road racing, standing miles and several other high speed racing events around the the country. some in car video would really cool to see of your car going those speeds.

 

here's two videos i took a while back:
https://www.youtube.com/watch?v=xQxv0FynRRA
https://www.youtube.com/watch?v=bOUCOD8k6z4

having driven countless miles on both us and canadian soil, i can compare driving styles on both sides of the pond pretty well. i believe the fastest i have seen was 70 mph in nevada.

one thing that really makes a difference is road quality. i assume there's a whole bunch of science behind road building, and during the last decade, the quality of the asphalt used over here has approved even more. it's very quiet to ride on and makes high speeds even more comfortable. no potholes on the autobahn either, the lanes are not very rutted and the roads are generally well kept.
another thing is the road layout. using the autobahn is almost like getting on a racing circuit. no stop signs, no traffic lights, no intersections, always closed off to the sides, no residential buildings next to it. so you can actually pay attention to what you're doing.
distance is also a factor. it's not that you have any large distance to cross in this country. it's pretty densely populated, you don't have to drive far to get where you want. so you don't drive top speed for hours, just for the next stretch in front of you.
in north america however, i found everyone to just go with the flow and letting it roll - being on vacation, i actually found that a more pleasant way to drive.

i'm very well aware of the fact that i'm putting myself at risk every time i get into that car... with no crumple zones but just 40 year old sheet metal around me i tend to drive fast, but carefully and always double check what the others are doing!

 

i remember hearing something about the autobahn being twice as thick as the american highway system, and this being why it holds up to time and wear so much better. i can easily imagine the strain of driving high speed over the going with the flow would be like. high speed evens done on occasion is a great treat but to have to exercise that level of concentration and what ever else goes into it would be a wearing endeavor, but fun on occasion. it is just cool to know that a comet is in this world able to go on the autobahn at speed at will.

 

From what I've read, they have rules, and they know them, kinda like here.

 

looks like i fixed both cars. both differentials are now tight, the pinion was loose on both causing bad vibrations.
the mustang was much worse than the comet, but that was also due to the fact that there was not much pressure left in the front tires. it helps to check the obvious from time to time
found something neat to check driveline angles, though: a smartphone app by tremec. will dig into that again some time soon. here's the link: http://tremec.com/menu.php?m=154

didn't drive the comet much yet, but it feels like it's revving up a lot easier with the aluminum driveshaft.

i also swapped out the outer tie rods. when i rebuilt the front end, i just used the ones that came with the kit. i was not aware that the disc brake spindles used different tie rods and always wondered why the cotter pin was sitting that high above the castle nut. i found a post by craig mentioning that also the taper is different, so something needed to be done. i had a spare set i ordered some time ago and now swapped them in while i had the car on the lift.

what i have to take care of next is my steering wheel. there's some play in it, at least that's how it feels. i'm pretty sure it's not in the column, the steering box or the rag joint. i'm using the ford sport steering wheel, and every time i turn in the other direction, i feel some play until it's tight again. so something must be moving internally? anyone know how the spokes are connected to the hub? is that a sign of something breaking? i guess i need to check it before hitting the autobahn again!

 

The only way I can see a steering wheel giving you that symptom would be worn-out splines and the center nut not being tight.

I think it is more likely something in the column itself. I be interested to see how this progresses.

Has your steering box been adjusted? If the gear meshing is loose, you might get that. There is a good procedure here somewhere how to adjust that.

 

I wrote that tech article on steering box rebuild
So I doubt it's an internal problem.

When turning the wheel, I can hear a slight scratching noise, which is not coming from the outside. then something hits and the steering wheel comes to a slight stop. Only then it begins turning the shaft, at least that's how it feels.

Will take off the horn button tonight to see whether i can observe something when the car is parked. What I suspect is the spokes of the wheel moving around the hub a little, but I'll try to verify that!

 

Too funny that you wrote the article ...I usually try to look these things up before commenting. Anyway, I remembered it was a GOOD article ... LOL

Here is an inside view of my sports wheel if this helps ....

 

still can't figure out how the spokes are attached... seems like they're welded.
after all, the steering wheel is not the source of the play in the shaft anyway. it's the rag joint. seems like there's play although the bolts are tightened - so it could be that they're too small in diameter and are floating around a little.
as the steering coupler is made out of poly, the noise is surprisingly loud and can be heard inside the car. once i looked under the hood and had my kid turn the wheel, it was easy to spot...

 

just received a replacement steering coupler from a mustang parts store.
even without taking mine apart, it's easy to see what's wrong. the coupler takes shouldered bolts, and the one i have on the car came with regular bolts. so that's where the slop came from.
i'm going to mix and match the parts a little, and use the proper bolts with my existing poly coupler.

 

steering coupler is back in. while the column was out, i was able to tweak some minor issues. rerouting some cables, adjusting the heater controls.

now i finally feel lucky i bought that parts car last year. just grabbing a good heater duct off the shelf to replace my brittle unit is quite nice...

 

attended a big car show last weekend.
here's a nice shot from friday evening: