Vibration at speed

Looking for some diagnostic help-
I have an 89 Si with B16A1, YS1 LSD tranny.
I have had an on going problem with vibration/shudder from the front end. It feels almost as bad as driving on the rumble strips on the shoulders of the interstate. It gets more noticable the faster you go. It was worse when my car was lower, then I adjusted my coilovers and raised the car back to almost stock height and it went away for awhile but now it is getting worse again. The minute the steering wheel gets a degree right of center it starts to happen worse and the more you turn it the worse it gets, even changing lanes on the highway does it. When going straight or to the left it does not happen unless you go over a bump or dip then it will do it. Before I rasied it it would happen going straight as well. The vibration is felt through the chassie and not as much through the steering wheel. I have rotated wheels tires, had new ones installed, and rebalanced and that did not help. I replaced the inner and outer tie rods off of the steering rack. I also had an alignment. I am thinking maybe wheel bearings? or my axles although they are new (93 GSR) and should not be a problem. Sorry for the long post, thanks for reading.

jack the driverside front wheel up off the ground w/o loosening the lug nuts, and try shaking the wheel, front to back and top to bottom. then do the same w/ the passengerside front wheel. if they shake, then it's the wheel bearings. the axels could be the problem if they r off balance, but not too likely if they weren't altered and installed correctly. could also be ball joints up front. check all 3 balljoints on each side and see if any r loose or any boots r split open or cracked.

sounds like driveaxle problems. does it only happen if you're in gear?

It will do it when I pull it out of gear and am in neutral but it is not as pronounced. I can also change it by giving it gas or letting off the gas, changing the amount of torque going to the wheels.

yeah sounds like ball joints or wheel bearing. do the tests i mentioned and that'll narrow it down further for ya.

might be the inner cv axle.. does it shake only on acceleration?

It does it on acceleration and decceleration, when I change the torque load going to the wheels. If I am at a constant speed it is not as bad unless I go over a dip or bring the wheel right of center at all, although as it seems to get worse it is happening while going straight as well. Thanks to all for helping me work through this.

Also check your motor mounts - I had my passenger side one loose and it felt like an axle or out of balance tire sometimes.

With the above mentioned things, you might also check your struts. Have you looked at your wheel balance?

My suspension is all 1 year old H&R coilovers, seems to be fine. I have rotated all my tires and just had new ones put on the front, new/old/rotated, made no difference. The vibration is much harsher than any out of balance wheel I have encountered. It shakes the whole chassie. It is just like driving over the rumble strips on the highway, only a lower deeper pitch.

Ya, check your motor mounts, make sure none are broken or loose.

alright, it does sound kinda like a bad motor mount. however, the increase in noise when turning slightly, makes it sound like a suspension issue. also, the statement of, "raised the car back to almost stock height and it went away for awhile" says suspension problem. how does it sound/react in rain or wet roads? louder/bumpier? if so, then it's definitely suspension, and most likely a ball joint or bushing. could be a wheel bearing. i'm telling u, the test i mentioned above takes like 15 min and it'll tell u straight up if it's suspension or not.

Motor mounts are all new hasports. I could not get any play out of anything when I did your test. It all felt solid. I have not noticed any differences in the rain but I have not driven all that much in the rain. I had bad inner and outter tie rod ends and replaced thoses. When those were bad the car did this same thing at slow speeds. When I replaced them, the problem went away at low speeds but now it feels like that at higher speeds. I was also wondering if it could be something with my LSD?

is there any shaking when you shift into neutral going at the same speed? i'm not sure about the shaking on decelleration part, but my problem was that the car's body shaked on acceleration above 60mph. i checked the innerboots and it had no grease in it. so i rebuilt it and it drives smooth. so check the innerboots. also, check the bearings, jack the car up and spin the wheels, it shouldn't make any grinding noises. if it does, then you need new ones.