Miata diffy, open rear.....

some of you know I got my wife a used Miata not long ago, so the diffy at freeway speeds and even in traffic, was not spotted right away, the spyder/side gears grinding....

all bearings are silky smooth, ring pinion have good backlash...just that when you spin one axel the side/spyder gears make a hell of a grinding sound...they are not meshing right....the side gears have way too much play in there....about 1/32 per side....like .030 something...so I was thinking of somehow getting those side thrust washers/bearings remade some 20 mills/side thicker to further enmesh the side/pinion gears...and quite down the rumble....

the wear pattern on the gears is totally negligible, there is no offsets in the surface...no wear pattern to speak of, just polished....

anyone with any thoughts...GARY???

rear has 130k on it from the clock anyway...oil WAS fresh...but lots of black sludge inside....fine ground metal particles....all washed out now....

Dude this is a corvette forum...

Just kidding with you. Try Miata.net as this is where I get info the the wifes car. Have you thought about picking up a used posi diff? Also make sure you run Redline gear lube as this seems to help. I also run it in the Miata trans and it did help with the 1-2 shift.

Yeh, I know, but you guys are the only group of serious mechanics I know of on the web....

so the Miata has a open diffy, had it all apart, and noticed the side gears are rather loose on the side washers/thrust plates....but it's less than 20 mils....

so the issue is....when spinning one wheel the other turns the other way, obviously, but the diffy emits a lo level growl...the oil and bearings and lash and patterns are all fine....so I put it all back together...the CV 1/2 shafts are fine too....listen with a stethoscope up in the air and no noise...bearings fine....nothing loose.....but when driving it....the turning left slightly increases the growling, turning right stops it...I look like a idiot on my new pavement street driving side to side, swerving hard......I thought drive shaft due to prompts....NO...not the diffy either....

thing is, does a open rear have a slight grumble to it when turning one wheel??? driveshaft still??? been so long, I really forget...

at this point, methinks I wasted 2 days labor for nothing, and it's nothing but wheel alignment....tire tread....

Are you sure it's the diff? Could if be a hub bearing? If the hub bearing is failing it could growl and if worn enough allow the rotor to move in the caliper maybe making it worse.

miatanet.com has some good folks on there as my wife founds some good tips on preping her car for track days.

daveL82 said:

Are you sure it's the diff? Could if be a hub bearing? If the hub bearing is failing it could growl and if worn enough allow the rotor to move in the caliper maybe making it worse.

miatanet.com has some good folks on there as my wife founds some good tips on preping her car for track days.

Click to expand...

Yes, and they have been helpful...got some trim parts, no problem...even affordable .....surprise....got a top for the vette and the Miata off ebay, same dealer....so two tops to do....vette after it's painted....

one guys there from down the road sold me a set of stock factory wheels for it....nice guy...almost identical car....white instead of RED.....but the price, with tires....80 bux....complete ready to go...tires were NEW but there ain't no Effin' Irestone from maybe 40 years now......

so the tire are now fine....

I needs to know about open diffy's though...is that rumble/grumble normal???

:surrender:

Cheap fix-- get your welder pal to weld the side gears to the case. No more noise, no more open diffy. :tomato: