Maruha LSD Vol.1



To install Maruha LSD for NA6CE(B6)/90-93model, the special out-put shafts is required. 
If your Miata is an open differential type (not viscus LSD), you can use stocks again for our LSD. 
Please check the following.

NA6CE(B6)/90-93model
The different length type on L and R : you have to change stocks for our LSD
The same length type on L and R : you can use stocks again for our LSD

On the later model since '94(NA8C / NB6 NB8) with more large differential, stock out-put shafts are unnecessary to change them. (Available reusing for Maruha LSD) 

We recommend you to use new parts of side bearings and side oil seals to avoid troubles.

(LSD lecture)

1.Introduction
Mechanical LSD and std LSD by Mazda (Viscous and Torque sensitive), these LSD are completely different on its mechanism, features and performance.

And mechanical LSD drives the general differential (usually called as open diff) out of tuning market in performance. (stable drive, climbing, cornering, acceleration etc) 

We are recommending for more enjoy driving of your Miata with Maruha LSD, this LSD is for not only circuit attack, 
but also drifting and winding roads. 

You feel chattering from LSD. In case of mechanical LSD, it is no-way to avoid. 
But Maruha LSD is designed as low chattering by low initial set up and with additive treatment. 
These chattering can be reduced by devices above. 


2.Open differential


The following parts are for open differential as components.

Side gear (x 2) -------------- to drive shafts (L/R)
Pinion gear (x2)------------ mesh with side gears
Pinion cross shaft (x 1)---axis of rotation for pinion gears

(Going straight)

The difference of turning speed between left and right drive shafts does not happen, and left and right side gear rotate together. 
So pinion gears do not rotate.

Example :
In put rotation to the differential (Finial pinion gear) 100rpm
Left drive shaft : 100rpm
Right drive shaft : 100rpm

(Cornering)

In case of turning to the right

The right drive shaft is in side (slow rotation), the left drive shaft is out side (fast rotation).
Then cornering is smooth.

Indeed, as an actual operation, the right drive shaft receives the load which makes slow down from the road. 

The right side gear rotates slower than the differential case.
The pinion gears rotate, and give the rotation speed of the spinning opposite way to the left side gear.
The left side gear rotates faster than a diff case. 

Slow rotation of the right drive shaft and fast rotation of the left. 
This balance is transmitted through a differential.
The difference of rotation speed between right and left drive shafts is adjusted to keep balance automatically based on the large load wheel. 

Example :
In put rotation to the differential (Finial pinion gear) 100rpm
Left drive shaft : 70rpm
Right drive shaft : 130rpm

(Demerits of a open differential)

Can not escape from a muddy place. 



When the one wheel to drive slips in a muddy place, the load of that wheel is zero(0), the opposite side wheel receives all traction. 

The grounded wheel dose not rotate.
The slipping wheel rotates with two times speed.

After all, a vehicle can not move at all. 

Can not transmit traction during hard cornering.

The inside wheel is rifted in hard cornering by centrifugal force.
In this case, the inside wheel lose the traction at the moment and down speed.

On usual driving on street, the torque of drive shafts changes constantly by affection from road situation and tires and keep balance through the differential. 

To cove this demerit of open differential type which is " traction concentrates on the low load shaft, LSD is required. 

LSD is the device to get the high driving force as much as you can. 


3.Maruha mechanical LSD


This kit is consisted by 25pcs parts.


Side gear (x 2)・・・Connecting to drive shafts (L/R)
Pinion gear(x4)・・・Coupling to side gears
Pressure ring (x2)・・・been keeping in a differential case, and can slide by cam mechanism.
Pinion cross shaft (x1) ・・・axis of rotation for pinion gears
Clutch plates (drive x4)・・・friction plates rotating with a diff case
Clutch plates (driven x4)・・ friction plates rotating with side gears
Spring plate(x2) ・・・pushing clutch plates at all times
Washer(x2) ・・・ receiving trust from side gears and prevent from blowout 

Pinion gear rotates based on pinion cross shaft, side gears mesh to pinion gears.
Pressure rings can slide and have ditch like V letter to set pinion cross shaft.

Pinion cross shaft floats between pressure ring (left and right) and not connect to a diff case. 

Pinion cross shaft is installed directly to a diff case on open differential

Each clutch plate (drive and driven) are set mutually between a pressure ring and a diff case.

(LSD motive power)

When accelerator on, motive power is input to LSD and pressure rings and a diff case start rotating together.
Drive shafts will keep the speed by inertia.
These both power (accelerator on / drive shafts) bump at V ditch between pressure rings and pinion cross shaft. 

Thus the gap comes out between pressure rings and pinion cross shaft (V ditch), pinion cross shaft push pressure rings to open, and clutch disks are locked firmly by sliding of pressure rings.

Side gears of left and right connect to clutch plates, lock ratio of side gears are changeable by V ditch movement as " cam function".
This cam function is by traction (acceleration on/off) and inertia (drive shafts rotation) to keep a balance.
Therefore it is called as " torque response type" . 
The mechanical LSD is not 100% lock type. 

We can change a feature of cam function. 

l In case of more wide angle of V ditch.
The force of Pressure ring opening is more strength. LSD effect is firm.　 

l In case of more narrow angle of V ditch.
The force of pressure ring opening is more weak. LSD effect is infirm


There are three types on cam function of V ditch.

1 V ditch with left and right symmetry----" 2way type "
LSD is effect when accelerator ON/ OFF both

2 V ditch with left and right not symmetry----" 1.5way type"
LSD effect is infirm when accelerator OFF. 

3 V ditch with vertical angle on the one side-----" 1 way type "
LSD effect is zero when accelerator OFF. 

(Initial torque)

Spring plate(x2) give pressure to clutch plates at all times
The friction of clutch plates by this pressure is " Initial torque".

Initial torque has two roles.

  1. Controlling cam function at the some degree → Preventing hunting by a little bit of torque changing.
  2. Assisting cam function when wheel slips→Improvement in pick up.

If initial torque is set as more hard, LSD effect becomes all time (Not torque response type), 
it would be cause of performance down of cornering.

To adjust these conflict roles, you should consider about your usage firstly and decide a spec.

Example :
Race, circuit, drifting ------High initial torque →The priority of LSD effectiveness.
Street-------Low initial torque→The priority of torque response