i got a question my rx7 vibrates on 3rd and 4th gear after like 3k and 4k rpm's no grinding tho. all the gears go in fine. when i put it in neutral it takes a min but then it stops vibrating. i checked my tires and tranny bolts and my ujoints on the drive shaft averythings good. i pulled the driveshaft and the yolk looked like it had wear on it and it looked like some of the metal on the yolk was ground off not by mutch tho. also when i pulled the drive shaft off there was any to none gear lube in the tranny. i kno that the tranny has to have at least 2qrts. 90wgear oil in it. i refilled it. what you guys could think its wrong? new seal for tail end tranny? new drive shaft? or new tranny? if anyone could help would b great. thanks for looking

 

If your not leaking tranny fluid i wouldnt see why you should pull it all apart to place new seals in it... unless you were only gonna do the seal in the tail shaft? If the joints in the drive shaft are good and tires arent your issue, i would look at mounts, rear end, and possible timing. Im a test everything you can think of kinda guy. It results in issues being fixed and lots of new stuff on my old beater

 

i'd look at, in this order:
1. wheel balance
2. mounts and bushings(remember the car is 25 years old)
3. uv joints/drive shaft balance
4. wheel/axle bearings

All 4 of those are wear items so theres a good chance its one of those on a 25 year old car.

 

There's a ton of moving stuff on a car, and with the big heavy stuff, if it's moving and out of balance, it WILL induce a vibration. Read what saleen06 posted. That's probably the cause. If it "slowly goes away" when you put it in neutral, that tells me that it's speed related. I'd be willing to bet it's a bad tire or wheel out of balance.

 

landon, your so smart So, to the OP...did you figure it out or what...?

 

im still looking. the tires are good and the rear end is good too. i mean a got a gsl-se rear end but its gonna b a headache right now to switch everything around i dont have the time. now my question is y did the driveshft was like purp when i pulled it offand had metal worn off on it? and how do i check the balance on the driveshaft? ima look into the bearings and the bushings. im also gonna chek the axle bearings is worth a try. i was about to get rid of it but ill give it a couple more tries. you guys are awesome thankx for real !!

 

oh when i drove the wippi today the vibration its on the middle of the car like were i shift at. any suggestions ???

 

check your UV joints on the drive shaft. If the splines on the output shaft are to worn out it might cause it. is it only on deceleration only or what?

 

nah while im driving too. its weird cause sometimes it will vibrate and sometimes it wont. and it only 3rd and 4rth gear on like 3,4,and at times 5k rpm's. my speedometer dont work(of course) so i dont really kno wats the miles. idk if i dont figure it out soon ima sell it. i really think its my tranny cause the driveshaft is good the ujoints are good rear end is good tires are good, im destroying my brain trying to figure it out.

 

did you take the wheels and tires off and put them on a ballance machine to see if they roll straghit? or if there is anything in them like fix a flat?