I have done a search on this and tried to study up first.

Had an engine drop (Clutch/LWF & top end) several months ago on my 993 C4S. Everything seemed fine (I put all new tires on at the same time) until a couple days ago at 70 mph and up I felt weird vibrations. Increasing noticeable as speed increases. I took it to 90 mph and the shake was not good. The vibrations were not in the steering wheel.

I took it to a different Porsche shop than the one who did the engine drop work. I told them about the previous work. They drove the car and said the problem is probably the alignment and that the only game in town to do a Kinematic toe alignment is the dealer.

I plan to have the dealer do the Kinematic deal. ($300) Does what I'm being told sound correct? The car is 99% bone stock...no Bilstiens, PS009 (?), etc. 50K miles, so yes I know the Monroe's are weak at this point, but everything was fine until a couple days ago.

If I do the Kinematic do they check other settings. I read for street use (Per Jeff in the Air)---

Front Negative Camber-about 0.5 to 0.75 Toe in-1/16"
Rear Negative Camber-about 0.5 degrees MORE than Front Negative Camber

What else do I need to know about all this? Why did it take 4K miles after the engine drop to start vibrating? The shop that did the drop did not have a Kinematic alignment done.

Thanks in advance.

 

I'd take the tires back and have them rebalanced. If they are OK, then move on to possible realignment issues. Do the easy stuff first.

 

Usually those shakes comes from balancing of tires, if not, then I would check on the bushings, and is your wheels in good condition ?