Toyota Diff Codes Debunked Finally???

[Makaveli]

While there has been some general consensus on Toyota Diff Codes identification & their meanings over the internet. I would like to raise some facts/concerns for others to ponder.

First Letter: Denotes Ring Gear Size. A = 138mm & B = 145mm

Second Two Numbers: Supposed to denote the Final Drive Ratio (I don't think this is accurate)

Last Letter: Supposed to denote type of Diff. A = Open Diff & B = Torsen LSD (I don't think this is accurate as C & D Types also exist).

I believe these letters & numbers have different meanings/interpretations depending on the model of the car. eg: A Letter means one thing for say Supra and means something else for a Chaser.

When I had a UCF20 Toyota Celsior with a A01A Diff, I have bought a A01C Diff from a JZX90 & the LSD would not fit inside. I have been told by the parts person, since this is the same series of diff, they should be swappable.

Please note: Some examples that have been confirmed by me and this is ONLY "MY INTERPRETATION".


Toyota Chaser Tourer V JZX100:
Engine: 1JZ-GTE
Transmission: Automatic A341E
Axle: B01B - Open Diff
Final Gear Ratio: 43:11 = 3.909

Toyota Chaser Tourer V JZX100:
Engine: 1JZ-GTE
Transmission: Manual R154
Axle: B02D - Torsen LSD
Final Gear Ratio: 41:11 = 3.727

Toyota Supra RZ-S JZA80
Engine: 2JZ-GTE
Transmission: Manual V160
Axle: B03B - Torsen LSD
Final Gear Ratio: 49:15 = 3.267

Toyota Mark II Grande JZX110
Engine: 1JZ-FSE (Direct Injection - Non Turbo)
Transmission: Automatic A340E
Axle: A03A - Open Diff
Final Gear Ratio: 41:10 = 4.100

Toyota Mark II Tourer V JZX90
Engine: 1JZ-GTE
Transmission: Automatic A341E
Axle: A01C - (Some say its factory Clutch LSD??? - not too sure myself)
Final Gear Ratio: 43:11 = 3.909

Toyota Celsior C Specification UCF21
Engine: 1UZ-FE
Transmission: Automatic A650E
Axle: A01A - Open Diff
Final Gear Ratio: 49:15 = 3.266

Toyota Altezza RS200 Z Edition SXE10
Engine: 3S-GE
Transmission: Manual J160
Axle: A03B - Torsen LSD
Final Gear Ratio: 43:10 = 4.300

Toyota Aristo V300 Vertex Edition JZS161
Engine: 2JZ-GTE
Transmission: Automatic A340E
Axle: A01A - Open Diff
Final Gear Ratio: 49:13 = 3.769

[gt4dude]

A few more codes for you from the Toyota Celica ST2**, may help you decide what's what


SS-I/MT/Open FWD: S54 / -04A
SS-3/MT/*LSD FWD: S54 / -06D
GT-4/MT/Torsen Rear, Viscous Centre, AWD: E154F / -08B




* We're still unsure what type of LSD, Viscous or Clutch-type was equipped in these higher spec FWDs.


.---------[ so D for Helical? ]
|
V

[xsspeed]

I am pretty sure the S54-06D is a helical lsd, it was also sold as a TRD mechanical LSD (I have one of these)

As well as S54-04A there are also S54-06A's as well (I have one of each)

[gt4dude]

How they work

The Torsen differential works just like a conventional differential but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR).[3] When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential.


If one wheel were raised in the air, the regular Torsen units would act like an open differential, and no torque would be transferred to the other wheel. This is where the parking brake "trick" can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, then the drag to the airborne side is 'multiplied' through the differential, and TBR times the drag torque is applied to the other side. So, the ground side would see (TBR X drag torque) minus drag torque, and hopefully that can help restore progress either forward/backwards.

interesting read, it's always good to know what your axels are doing so you can drive accordingly

[xsspeed]

I dont think it is as simple as D for helical, b for viscous, c for whatever, as makaveli wrote (and I think I came to a similar conclusion) the diff codes are relevant to a particular box or chassis.

I think I found instances of the same type of diff being labelled different letters when I was trying to unravel it (but were in different cars).

What type of lsd is in a c56-04c? some type of torsen? so helical as well?

I think I made a post last year sometime with some info in it, and Mark/Ae25 has written some stuff either on here or toymods as well