There is a pulsation coming from the rear of my Evo IV GSR, it is related to speed and starts around 80km/h. It's a dull, half-second vibration that occurs every .5 to .75 seconds. As speed increases, the vibration and noise increase slightly and the vibration frequency increases to about .75 to 1 seconds. I can feel it in the brake and throttle pedal.

My AYC and rear diff fluid is brand new, and I've never heard any other strange noises from the rear end (donkey noise). Ive searched around and the only other people who have had this problem have aftermarket parts installed or it happened around a corner. My rear end is 100% stock and this vibration persists in both straight lines and corners. Any ideas on what this could be?

 

tires need balanced

 

I installed and balanced the wheels myself so I know it was done correctly. This isnt a constant vibration; its a slow, on and off pulsation. Ive worked in a tire shop for over a year and I've never had a wheel vibrate like this.

 

wrong fluid causing chatter?

 

Does it do it in any gear besides 5th?

 

I just took it out on the highway and only felt the pulsation in 5th. It's worth mentioning that for the first time I heard some clicking/snapping in the rear end. It occurred after a hard 2nd gear engagement during acceleration onto the highway.

 

Can you feel it on the floor of the car as your foot rests aswell? Maybe a weight fell off your driveshaft, bad joint in the shaft possibly?

 

sounds like your differential is somehow fusing together...those idiot ricer drift kids that weld their diffs or get certain diffs made for it get this problem, it's like those girls that pay more for pants with holes in them already...

 

My Evo VIII does the same thing (the vibration). I suggest you check with one or more of the transmission builders. I'm thinking they may suggest the problem is a loose 5th gear on either the input or output shaft of the transmission. I plan on having my transmission rebuilt when the clutch goes.

 

I can feel the vibration only slightly on the floor, though it is mostly noticeable through the pedals. If it is my 5th gear, is it safe to drive like this?

Also, I don't believe the previous owner welded the rear diff and drifted with it. It was a one owner car that was freshly imported from Japan and came in impeccable condition. Kudos to JDM Connection

 

I've been doing it for 65,000 miles. However, if my diagnosis is correct, I will probably need a new main shaft as well as a fifth gear when the time comes. The gear is chewing up the shaft.

 

Very good then, I can live with it for the time being. I was planning on doing a VI engine swap and throwing some crazy, bulletproof transmission in there; and this will give me a good reason to do so.

Thanks to everyone for all of your help and wisdom!