i heard that a '94-'97 miata rear end fits with the first gen. RX-7, is this true???? mine is a '79, i would like to know if it dose or dosent. thanks.

 

It is my understanding that the Miata Pumpkin will fit the 1st gen axle housing and the 84-85 axle shaft splines.

 

'94-up only, but yes....

 

94 and up miata will fit the '79??

 

The '94-up Miata will work in an '84-85 rearend. It will physically bolt in to any 1st-gen rear but only the '84-85 have the correct axle splines. You cannot swap those axles into an earlier housing.

The only point to the swap would be so you can use the lower gears and/or Torsen diff found in SOME Miatas. Other than that, not much point.

 

Is there something wrong with lower gears or torsen diffs?

I know there's one problem with torsen diffs:
They don't work if one wheel has absolutely NO traction. Thus solved by applying the brakes lightly.

The benefits are:
No special fluids required. Striaght gear oil
Never wears out unlike clutch pack diffs
Stronger than other types of diff

Any others? Any corrections as well.

 

Torsens aren't the strongest... they still use gears and gears can break. I'm sure SOMEONE out there makes a spool for the Mazda 7"....

Which is my point. The '94-up Miata differential is the same short-nose 7" that was used in the 1st-gen RX-7 as well as the RX-3 SP. There's no inherent advantage to using it unless you grab one with the torsen diff or with 4.30 or 4.444 gears. (Forgot about those...) Conveniently the Miata halfshafts' inner splines are the same as the '84-85 RX-7 axles' splines.

I kinda like the clutch LSD. It chirps around tight corners just like a spool

 

Other than what thread and cable come on, or what my coffee table will be made of, What's a spool?

 

spool - A one piece ring gear carrier that locks the rear axle shafts together and provides equal rotation of both wheels.

As taken from the Summit Racing online catolog.

 

something i dropped in the toilet earlier.

 

Which consequently makes it very difficult to make a low speed turn or drive in the rain. Unless you have a V8 with lots of torque. Then it becomes very fun. (Much like the big block F body I had )

Harsh on rear tires on the street, thats why they are recommended for drag use only. The same effect without the strength is obtained by the fools that weld their spider gears.

 

quote from How stuff works.com

", the Torsen is superior to the viscous coupling because it transfers torque to the stable wheels before the actual slipping occurs.

However, if one set of wheels loses traction completely, the Torsen differential will be unable to supply any torque to the other set of wheels."