Bad vibration at 3000 RPM's and up

[Badlilstang]

The only axel bearings I know of are the ones pressed into the axle tube part of the rear end. The carrier also has its own set of bearings. I would pickup a polyuerathne (sp?) mount for the tranny. I avoid these mounts on the SN95 cars as ive had them introduce new vibes but the crossmember on the fox cars still has bushings on the ends connecting to the body. If your car doesnt vibe with the your buddies driveshaft installed then atleast you can rule that out. Make sure his car doesnt have a vibe too before you use it

 

[91 foxbody]

I had a violent vibration problem too. My shifter know would not even stay tight so i took it off. I did several things at once so i really dont know for sure what corrected the problem. The vibration was so bad at higher RPM that if i put my hand on the shifter it actually hurt. Here's what i did. I had just replaced my gears,inner and outer bearings in the diff. It was fine at first, then the vibration started. I put the car on stands and tightened down my pinion nut, there was some play in it. Then i moved to the front of the car, grabbed my wheels and 9 and 3 and had ALOT of play. It was my inner tie rod, the one connected to the rack and pinion. I installed a new rack and pinion and while i was at it installed a new harmonic balancer,rotors,brakes and inner and outer bearings. I still have the stock driveshaft and the car drives great now. Any way that was my long drawn out expereince.
Keith

 

[91 foxbody]

i meant to say shifter knob would not stay tight. Anyway grab the rear of the drive shaft where it goes into the diff. push and pull side to side and up and down. If you have play then tighten the pinion bolt,( you will have to disconnect the drive shaft, you will need a impact wrench or a 1/2 inch ratchet with a 1 and 1/16 inch socket as well as a cheater bar and a bunch of ass to tighten it, but as mentioned before not to tight. When i rebuilt my rear end i guess i did not crush the crush sleeve all the way that is the reason it was so hard,but if yours is stock,the crush sleeve is already crushed so it might not be as hard to tighten it.If you have never installed gears it is kind of hard to explain how to do it, i can do it by hand now. Drain your fluid you will have a magnet inside the pumpkin or at the bottem of the fill nut, check for metal. Get some BLUE RTV and go around the the cover, this is better than a gasket. Fill it back up with a bottle of heat reducer. Put around 100 miles on it and drain and repeat process. I would go ahead and put some new gears in there. You do have to take axles out to do this. Make sure you have a micrometer to set lash correctly. You can press inner and outer bearings yourself. I always have to get the pinion bearing pressed on. Find a local garage and they will probably do it for free or maybe a six pack.

 

[Bakedrubber]

I have a 89 LX.When I get at 3000 RPM's I got a vibration that you can feel thru the whole car. And the faster you go the more louder and worse it gets. I had the driveshaft balanced and u joints are good. Just had the motor rebuilt and they checked the balance with my flywheel and pressure plate. But now they marked for me how my pressure plate should go on my flywheel with 2 yellow paint marks. But I had to get my flywheel turned and the machine shop who turned it removed the yellow marks so I had to just guess how I thought they had the pressure plate lining up on the flywheel. So in a nut shell I just rotated the pressure plate until it lined up on the flywheel and I bolted it down. Now I know its not tires either because I just put new wheels and tires on it the other day and it still does it. At 2500 in 5th gear you start to get this vibration that comes and goes comes and goes. Its like every 1-2 seconds it vibrates and then as your speed and rpms increase it s steady and just gets worse as you increase the speed and rpms. I just rebuilt the tranny. I dont think thats the problem. Unless the main shaft in the tranny is bent a couple thousandths. The only thing I haven't looked at is the rear end. I have no idea at what I would even look for. I dont know anything about rear ends or gears. I know it is a 4.10 and its 5 lug. Couldn't tell you when the fluid was ever changed in it. I know that wont fix it. So any help would be appreciated

I've had same issue since I bought my 89 gt back in October. I've had everything upgraded with brand new parts from flywheel back to rear end. Pilot bearing, flywheel, trans (TREMEC tko 500) driveshaft and yokes and all hardware. Still getting vibration. It turns out that I have a thrust bearing issue. They tend to wear out close to 150-200,000 miles. Idle fine and drove great

I have a 89 LX.When I get at 3000 RPM's I got a vibration that you can feel thru the whole car. And the faster you go the more louder and worse it gets. I had the driveshaft balanced and u joints are good. Just had the motor rebuilt and they checked the balance with my flywheel and pressure plate. But now they marked for me how my pressure plate should go on my flywheel with 2 yellow paint marks. But I had to get my flywheel turned and the machine shop who turned it removed the yellow marks so I had to just guess how I thought they had the pressure plate lining up on the flywheel. So in a nut shell I just rotated the pressure plate until it lined up on the flywheel and I bolted it down. Now I know its not tires either because I just put new wheels and tires on it the other day and it still does it. At 2500 in 5th gear you start to get this vibration that comes and goes comes and goes. Its like every 1-2 seconds it vibrates and then as your speed and rpms increase it s steady and just gets worse as you increase the speed and rpms. I just rebuilt the tranny. I dont think thats the problem. Unless the main shaft in the tranny is bent a couple thousandths. The only thing I haven't looked at is the rear end. I have no idea at what I would even look for. I dont know anything about rear ends or gears. I know it is a 4.10 and its 5 lug. Couldn't tell you when the fluid was ever changed in it. I know that wont fix it. So any help would be appreciated

I've had same issue since I bought my 89 gt back in October. I've had everything upgraded with brand new parts from flywheel back to rear end. Pilot bearing, flywheel, trans (TREMEC tko 500) driveshaft and yokes and all hardware. Still getting vibration. It turns out that I have a thrust bearing issue. They tend to wear out close to 150-200,000 miles. Idle fine and drive great until I leaned on it a bit then vibration from
great until I leaned on it a bit then vibration from hell at 3500. My rear seal kept blowing out. Replaced it twice in 3 months. Keep an eye on oil pressure !! So I'm getting a crank kit with new bearings and it should ready to rock and roll here in a couple weeks.

 

[Bakedrubber]

Crank kits with bearings through summit are pretty cheap

 

[Auto Reverse]

I had the same issues as OP. All it was was a $120 balancer. Replaced. Car was happy again.