Whoa. I didn't know this rumbling noise was so common. I have a 73 240Z and also have this rumbling noise that occurs, but only at times. My suspension is lowered (about a 4" clearance off the road), so I was always told by mechanics that the angle between the U-joints to the driveshaft/differential is the culprit (because the car is lower than stock). The rumbling on mine however, occurs only at times, which I have no idea why and it can drive me nuts. I do notice that it is most prominant on my Z between the speeds of 50 to 65 mph. So I just cruise between 70+ mph whenever I can. My car just purrs over 70+. However, the officers never believe me when I have to explain this to them.

Dan.

Most likely the driveshaft u-joints are bad. Pull the driveshaft and have them replaced. While you are under the car, replace the transmission and the front diff mounts.

John,

Replace the transmission? Why? Also, the Front diff. mounts? Not clear on what `front diff. mounts are'.

Dan.

Transmission mount. Typing problem on my part. The diff mount is the rubber mount at the front of the differential and you'll be working around it when you're unbolting the driveshaft.

I am having my struts replaced next week - scheduled with the Z-Man at `Z-Specialies' in Clearview WA to do the work. I will also him take a look at what you recommended regarding the U-Joints and mounts.

Thanks for your reply.

Dan.