I've searched, but did not find any problem like mine.

My original problem was that there was a clunk in first gear. Mazdatrix says it's the front u-joint, so i replaced the driveshaft with one of their aftermarket driveshafts. The clunk is gone, but now there is a new problem that wasn't there before: high speed vibration over 60 mphs. Most noticeable in 5th gear and NOT dependant on rpm. It's really bad and feels like I'm in a massage chair. Mazdatrix says vibration at high speeds is caused by bad rear u-joint. So I replaced that. Problem still not fixed.

Any ideas? It can't be the driveshaft cus it's new, but I think it has something to do with the driveshaft since the problem only started after I put a new one in. Anyone ever used weight washers on the bolt holding the driveshaft as mentioned in the FSM? Would it need weight washers? Mazdatrix's aftermarket drivershafts are balanced before being sold.

 

do you have your tires balanced right, and are you for sure the problem is in the rear of the car.

 

make sure you wheels are balanced. i used to work at a wheel and tire shop. thats your best bet. if the problem is still there, shake your front end down ( lift the front of your car up, wheels off the ground, put one hand on the front of one wheel and the other on the rear, shake back and forth rapidly. if it feels loose, or you hear and feel any clunking than you have a bad tie rod end somewhere, either inner or outer. do this for both sides. also, to check your wheel bearings, do the same thing, but up and down. put one hand on the bottom inside of the tire, and the other hand on the top outside of the tire and wiggle up and down, in and out rapidly, same thing. if you feel any clunking then you got a wheelbearing you need to re-pack or replace. hows your alignment? is your car lowered with no camber kit?

 

hmm...i think i need to replace my tie rod ends and repack my wheel bearings.

 

I had a similar problem in my old S5. The cause ended up being the rear tranny seal had gone bad and the shaft was bouncing around (severely in 5th gear). Check for fluid around the rear of the tranny.

 

alignment/bearing/tie rod ends before you check anything else

 

i fixed my vibration problem. for me, it was a bad transmission. i would have never thought. replaced driveshaft, half-shaft...then finally the tranny and the vibration is gone.

i just replaced my transmission so i thought it couldn't have been the transmission. it was. i got a free one from my bud slpin and now the vibration is gone. now i have a vibration at high rpms (5.5-6K+). im thinking it might be my clutch fan since my original went bad and i just put an s5 one on as a temp.

 

Thanks for all your input. I ended up buying a rear u-joint from mazdatrix because I thought that was the problem. I had a shop replace the u-joint for me and when I put the driveshaft in, it still had the vibration. I drove it like this for 2 months and today I tried adding grease in the rear u-joint. The problem has improved greatly. I guess the shop didn't grease it up for me.

Gonna do an alignment next. If I do a swap, I'll put in a different tranny too.