Is my gsl-se supposed to have posi-trac? it used to spin both of the tires but now it only does one wheel peels... did someone just spot weld the spider gears or did it used to have posi?

 

I has/had a limited slip differential. Sounds broken to me though. The GSL's and GSL-SE's are the only RX-7s that came with them.

~T.J.

 

The LSD in 1st gens is multi-plate clutch based... Like any clutch, they wear out over time and quit working.

You may choose to replace them, or you can upgrade to a Miata (Touring or S type only) TorSen type differential. This is gear based and does not wear out. You get 4.30:1 rear end ring and pinion in the deal. It also has better torque transfer from the slipping wheel to the gripping wheel.

It requires slight modification to fit, but it should bolt to your stock axle housing, and the splines in the Miata's half shafts are the same as the splines in the later (Series 3 : 1984 and 1985) axle shafts.

 

grrr...you just hit a pet peeve. I'll try to stay docile.

"posi" is a GM term for a limited slip differential. Just like "trak-lok" is for Ford. I'll leave it at that. If you had a "posi" in your RX7, it'd be a 10 bolt or some other stupid GM rear.

As it is, Mazda did equip your car with a limited slip differentil from the factory. Mine was in pretty foul order until a couple of days ago. I threw in some Amsoil synthetic 75w90 gear oil (designed for LSD's) and WHAM both wheels-a-spinnin. Of course, they only spin when I drop the clutch over 4k...but they spin!

Try swapping out the fluid. It takes about 2 quarts. I would suggest the Amsoil or Redline. If you experience "chatter" (I didn't) put in a bit of Redline friction modifier until it goes away. It makes a HUGE difference!

 

Or you can do as Pele suggests!

Pele, one question - I am heavily leaning towards this on my blue car - do the axles need to be from an -SE as I have heard, or are all 84-85 axles compatible? I am very interested in this mod for when I am making much, much more power (an extra couple - few hundred over stock).

 

you can also rebuild it. if you want it super tight, mazdatrix sells competition clutchplates that are thicker. i think just replacing clutch packs is around $150. cloud covered the pet peeve. i would also suggest redline.

 

Im thinking that I have posi, because over the winter I had one wheel on ice, and the other on dry pavement, and the one on the dry pavement was smoking!

 

That dont matter

 

Actually, that's an excellent test for seeing if you have LIMITED SLIP or not.

Put one wheel on grass or ice

drop the clutch

if both wheels leave nice patches (or a groove in the dirt or ice), you have limited slip

if only the wheel on the grass or ice spins, and the wheel on pavement just sits there, or spins, but not much, you have an open differential.

that's why lockers are used on 4x4's. If you have open diffs on a 4x4, when you get into a situation where one or two wheels have less traction than the others, (for instance, on a side-hill, or in a mud bog), the wheels without traction will just keep spinning like mad, and the wheels that are firmly planted on the ground will just sit there doing nothing... not good...

 

You definitely don't have posi. I'm guessing if you had swapped in a GM rear end, you'd know it.

 

The only reason why I think that, is becasue the original owner, is the owner of Rx7 in Rosville, MN. Ive had many conversations with him (Tony), and it seems that hes done many things to this car, that I never knew about!

 

OR just watch My Cousin Vinney