Dennis Parker

I some how ended up with two 10ae rx7s.. one is rolling chassis which eventually will become a drag car...the other one has 33k on it and is a garage queen..the 33k one has a strange shake at 52mph on up..I believe it has something to do with the front mount on the differential getting soft/

cracked with age...my question is..is replacing them going to suck as bad as it looks like it will?

Baldy

Front diff mount isn't hard to replace, it's more...tedious. Usually though, when it's bad, you get a very audible "THUNK" on acceleration. If you're having a vibration, it's probably something else. Tires or driveshaft, something like that.

leetfade

I would start with something simple like tires, as Baldy mentioned. You likely have flat spots on the tires with that low of miles.



Just take it in somewhere to have them balanced. It will be blatantly obvious if the tire is out of round or if you tossed a weight somehow.

Dennis Parker

I should have completed the story...The tires are new and roadforced at 7lbs, replaced the drive shaft with a new one with the replacable ujoints...stethed the trans and rear end and got no metallic grinding noises...the one thing that leads me to believe that the front mount is not broken but soft is that when its cold the vibration seems to be less noticable..rubber stiffens when cold....thanks for the responces and let me know your oppinion on this theory....thanks..

Baldy

Even with the front diff mount completely trashed, I'm pretty sure it doesn't cause vibration at speed (someone correct if I'm wrong), it just makes the diff pivot up and down when power is applied.



Did the shake exist prior to all the things you replaced/changed? Have you done the bearing check (jack up the car, pull/push on the wheels)?

Dennis Parker

the shake was there before and nothing has made any difference..I replaced the front wheel bearing but made no difference...it's been an agravating experience too say the least...I've stethed the rear bearings along with yanking on them and found nothing strange there...If the rear mounts,including the top mounts, don't do it the only thing I can think of to do is to put it on a dyno and lay underneath it until I can figure out this problem...that will be a creepy experience....also I disconnected the rear c.v shafts and ran it on stands, still shook, but if the rear diff was out of it there shoud be a noise that sounds like a corn sheller...but it's quite as a church mouse.there also was no metal filings in it. but it will shake at speed even with the clutch in and out of gear on a coast..maybe it's a built in system so I won't drive it fast enough to get a ticket in it...

Baldy

Anything unusual when revving in neutral (while standing still)?

Dennis Parker

not a thing...I wondered about exhaust resonance but I factored that out..it's a really confusing problem...

RONIN FC

Warped rotors? They could be throwing your calipers around at speed. Alignment issues can also cause unusual shakes at very specific speeds in these cars.



Go for a long ride, something should show up eventually.