mtndew

so i just bought an 85 (12a), but according to the previous owner it has the LSD. i was on my way home last night, started it up, got on the freeway and it was making a horrible whirly whiney noise and vibrating my teeth out of my head. it wasn't doing it when i was accelerating but was when i was coasting cruising and decelerating. it was definatly coming from the rear end. before i could even get to the next exit there was a loud pop, sparks and my drifeshaft was hanging on the ground (sheared all the bolts off). we ended up towing it home on a dolley (rear wheels on the ground) and the diff was still making a little noise when towing but not nearly as much as when driving it. anyone know what this could be? did i blow my diff?

Im kinda working on the conclusion that its shot and i need to get a new one, since i dont have the tools or the confidence to replace just the diff I've been looking for a whole new pumpkin to just replace the whole thing so i dont have to deal with adjusting backlash etc.. which brings me to my next question, ive noticed in the fsm that th 85 has drum brakes in the rear but mine has discs. is this because its the LSD? and if so assuming i cant find another LSD will i be able to use the discs on an open diff? im guessing an open will be easier and cheaper to find

mtndew

One thing I just thought of, the previous owner told me the pinion shaft bearing was starting to go and I could hear it a little when I test drive it. Could it be that the bearing ate it and that's what caused the drive shaft bolts to shear?
I'm just kinda starting to second guess the diff being the problem after talking to a tech at an rx7 shop around here who want so convinced, and the fact that it rolled just fine when being towed/pushed

Rhyno2050

Was there any play in the diff that you could feel, like a sudden jump from the diff?

mtndew

I'm not quite sure what you mean. There was nothing I could hear/feel while driving it on the test drive except a clicking noise that the guy said was the pinion shaft bearing. Other than that it ran smooth. Later I ran out of gas getting on the freeway (didn't realize that's all it was at the time) so I tried to compression start it in 3rd at around 40mph. Then once I got gas and started driving again that's when it started doing it so I think it's something I did but I don't know what. I was thinking I toasted that bearing when I tried that our something. I heard someone else describing a similar problem which turned out being a u-joint but as far as I can tell both off mine are fine (except for a zerg fitting being chewed up from dragging on the ground) again when accelerating it's smooth but holding speed or decelerating it's horrible noises and trying to vibrate the car apart

Rhyno2050

I was thinking that it could most likely be the u joints causing the vibrations but if they are fine, my other guess would be the yoke spline that could be worned down causing the vibrations in the driveshaft. the shaking mostly likely caused the breakage. hope this is of any help

mtndew

So definitely the diff. Finally got it up in the air and there were some pretty gnarly sounds coming from it. Cracked the drain plug and it was filed with metal chunks so I get to go pick up a new diff tomorrow for $400 (whole axle) and maybe a new drive line. But at least I'll be back on the road soon. Just gotta worry about my loose steering and lack of wipers and gauges now

Rhyno2050

so what cause the driveshaft to sheer off the diff?

david patterson

i have 92 model rx7 which is doing strange things at the rear, and am begining to think i may have a diff problem also. when put under load or high speed i am getting a nasty clonk and vibration that feels like i am driving on a square wheel. i have also noticed that even at slower speeds the car feels as though it has the handbrake on. this is intermittent and clears itself, so i am a bit baffeled as to where to start. anyone any ideas