Ok guys, here is one for you guys. My 2000
Boxster
2.7, 185,000 miles, has a tracking issue in the rear. When going down the road in a straight line 50 mph and above, the rear end darts back-and-forth almost like you were driving on some kind of grooved pavement.  it’s not like the car is fishtailing, it’s just a wiggle.  i’ve had the car up on Jack’s and been all over underneath. I see nothing loose or out of place. I’ve pushed and pulled and tugged on everything. I’ve checked every nut and bolt on all of the suspension sway bars, etc., nothing loose. Wheel bearings are good, shock mounts are good. I’ve had it on jackstands with the rear
tires
hanging free i.e. no weight. I’ve had it on jackstands and then jacked up each tire so that it is holding weight and checked it for anything loose.  I changed my
tires
,
Michelin pilot sport
, and put my sticky track
tires
on. It still does the same thing.  the only thing that I can figure is it may be the steering rack. I don’t feel any play in the wheel. I don’t feel any play while driving and the rear end is wiggling. Recently change the front motor mount  so that is good. I have never changed the two transmission mounts. This has got me stumped. I’ve owned the car for 13 years and put 100,000 miles on it. I’ve never seen or felt anything like it. has anybody got any  bona fide ideas. Please, no jokes, I’m way past that. thanks in advance.
Improper rear toe settings can do exactly what you are describing. When was the last time you had an alignment done on the car? Especially since you say you just had a motor mount changed out.
I cant say for sure on your model as its been a very long time since I owned my
986
, but in many cases there are support brackets or pans below the engine that are part of the suspension connections, and removing them for access to things such as motor or transmission mounts can require a realignment afterward. Did you only start to notice this issue after the motor mount replacement?
Lowering a car can also create this toe issue in the rear if aftermarket adjustable toe links aren't also installed in order to get the proper values back.
You are sort of talking about threshold braking wiggle. Alignment shops love to add more toe in in the rear to take care of this issue but really, they are missing the center puck on the LCA.s rubber wearing out allowing the LCA to move around. My shop told me that the rear axle can move almost 3 inchs forward and rear with a worn out center puck thrust bushing. Tarett makes a solid red one that will fix you up. Do both sides and report back.
