I have a 1985 Mazda Rx-7 GS with a new engine, fresh engine oil, fresh rear axle oil and fresh transmission oil. However, the noises still persist after the fluid changes as they did before the fluid changes. The problem is this. When I am driving the car in 3rd or 4th gear, there is a loud rumbling noise that seems to come from the rear of the car if the RPMs are below 2000. I can also hear an occasional metallic clanking noise when starting off in 1st gear or when just cruising along. I drive this car 150 miles everyday and believe me, this noise is new to me. Does anyone have any thoughts? I have nearly 179,000 miles on the drivetrain.



Before this noise started, I did a few things to the car:



*tightened a loose bolt on the front-right gas tank strap.

*removed the entire watts link, replaced the bent link on the right, greased the bolts that go through the link's bushings as well as the stud that the link mounts to and reinstalled everything.



Anyone who can try to shine some light on the subject, please do! I've tried to locate the noise, but I'm unable to do so, as "re-creating" the noise requires me to drive the car.



I hope I didn't ruin it. I feel very sad. https://www.nopistons.com/forums/pub..._DIR#>/sad.png

Does it make a kind of "Bed Spring" squeak when driving EXTREMELY slow?

Usually while going forward but not in reverse?

I don't know about a springy noise, but if I go real slow in 1st gear I can hear the driveshaft or gears whine, almost like an air noise - but I think that's normal. What would a springy noise mean?

check your universal joints on the drive shaft.

if you have limited slip, did you add the locker additive to the rear when you changed fluid?

This is a very old 1985 open differential, non-LSD. When I last checked the u-joints on the driveshaft, they were in OK shape - that was 17,000 miles ago. This rumbling just started three days ago with no prior notification, which is strange. Also, when I have the car up on jackstands and I try and turn the driveshaft by hand, there is noticable free play in either the transmission or differential, of which I am not sure of.

The "Bed Spring" noise is the sound of dry U-joints.

Since you "re-located" the rear end (IE replaced bent Watts link component), I

was thinking maybe the driveshaft didn't like the new angle.



I have an '85 GSL with rear disc and limited slip (non SE model), is yours a GS

or GSL?



Also, this may sound stupid, but change the tires from front to back to see if it

is tire noise.



One more thing to look at is the clearance between the exhaust pipe and the

rear axle, they might be coming into contact with each other.



Another is the trans mount.



Hope this helps.



Raul

Yes, this is a GS model. I will replace the driveshaft today and see if it helps. I don't think the transmission mount is bad, but I'll check. I will also check the exhaust clearance. Thank you for your help. I will let you know how it goes. https://www.nopistons.com/forums/pub...DIR#>/wink.png

Replaced the driveshaft with a new one from Mazda and it helped greatly. Shifts smoother and less of that annoying clunking during shifts. The rumbling is still there to some extent, but it's much better. I checked the exhaust and it clears the rear axle. Also checked the trans mount and it's fine. Checked the front wheel bearings and they are good. Maybe the rear axle? I don't know https://www.nopistons.com/forums/pub...R#>/unsure.png

I have a 84 GS and it had the same noise. mine turned out to be a crack in the diff by the mount for the spring. it was wide enough to stick a nickel in. so I swaped to a gsl rear and problem is gone

You know what? That might be the case because that's where I usually jack it up. Darn it! I'll have to check that out. Maybe it can be welded.