Doing some more reasearch into Diff for the Coupe. What ratio's are people using?

Im running a 3.89 : 1, CA Box and 185/60 r14 tyres on the rear. Dont want to change the rubber yet but at 100 kph it's pulling 3000 rpm. Its great fun aroung town, but not much fun on the freeway.

Cheers

ive got 3.7 and 195 50 15s. its around 3000rpm at 100kph and rev limiter in 5th would be around 200kph

if you have a normal CA silvia box, you could always swap to an SR turbo box as they have a .73:1(i think) 5th instead of the .86:1 that the CA box has. so you wouldnt loose any acceloration in the lower gears but you would have a better cruising RPM. im doing this when the CA goes into the wagon but using an RB box instead of SR

think i worked out i could run the RB box and 3.9 or 4.11 diff gears instead of the 3.7s and still have the same cruise RPM

Will look into that PIGDOG. Cheers

Anyone else?

hey will a fairlane center bolt into the r31 diffs cos i want to go LSD

if its a borg warner 78 diff yes it will go
they came in heaps of cars
cortinas, centuras, p76s, falcons, commos, skylines
so heaps of brake combos, ratios and stud patterns avail
351 xd/xf came with 28 spline 4pinion


for pigdog
nissan gearboxes


Engine Type Part# Style Input gearset 1st 2nd 3rd 4th 5th 6th Reverse
N3130 Close Ratio OD 2.906 1.902 1.308 1.000 0.865 3.382
N3030 Wide Ratio OD 3.321 2.077 1.308 1.000 0.865 3.382
N3220 Opt 1 Race 2.818 1.973 1.470 1.192 1.000 3.382
N3221 Opt 2 Race 2.348 1.601 1.296 1.138 1.000 3.382
N3222 Opt 3 Race 2.192 1.601 1.470 1.138 1.000 3.382
N3201 Rally 2.192 1.601 1.470 1.138 1.000 3.382
FJ20 Turbo 3.657 2.177 1.419 1.000 0.833 3.382
SR20DET S13 180SX 3.321 1.902 1.308 1.000 0.760 3.382
SR20DE S15 Silvia 3.321 1.902 1.308 1.000 0.838 3.382
SR20DET S15 Silvia R 3.626 2.200 1.541 1.213 1.000 0.767 3.382
Z18 Turbo
CA18 Turbo (S13) FS5W71C 3.321 1.902 1.308 1.000 0.838 3.382
CA18 Turbo (S13) FS5W71C Euro model 3.592 2.057 1.361 1.000 0.821 3.657
240Z, 260Z R30 & 31 SKYLINE,
SR20, FJ20, CA20 FS5C71B Close Ratio 22:31 3.321 2.077 1.308 1.000 0.864 3.382

720 or NAVARA Utes, 280C,
280Z, R31-CA Pintara etc
FS5W71B Wide Ratio 21:32 3.592 2.057 1.361 1.000 0.852 3.382

Info from David

FS5W71B
F=FLOOR SHIFT, R=REMOTE SHIFT,
S=OD,W=WARNER SYCRO TYPE[SOME HAD SERVO TYPE?]
71 = MM BETWEEN SHAFTS,ABC = REAR HOUSING TYPE.
OUTPUT SHAFT =30.5MM 27 SPLINE. 81 TYPE IS 31.5 MM

I HAVE NOT HEARD OF THE C=CLOSE RATIO,BUT OLD 810 SSS AND Z-CARS HAD THAT NON-OD 5SPEED BOX AND IT HAD A STRANGE ID.

R31 EXCEPT RB20ET,RB20DT,RB30 HAD VERY DIFFERENT BOXES UNTIL AROUND 1986/06 IN JAPAN AROUND 87 IN AU THEY
STANDARDISED EXCEPT FOR SYCRO ON 4 CYL. THE AUSTRALIAN ONLY CA20 HAD A 910 SER3 TYPE BOX WITH
C REAR HOUSING. 71 MM BOXES

MODEL|ENGINE|COUNTRY
R31CA/RBAU O.321,1.902,1.308,1.,0.838,3.38
MAIN 22,33,27,26, ,22,36
COUNTER 31,14,20,28, ,37,15
MIDDLE EAST MODELS HAVE 21:39 OD GEARS
OTHER B TYPE 22:38,24:45,21:44,24:44,
C TYPE 21:39,22:37,

910 L20B/CA20S AU 22,33,28,26, ,26,36
31,14,19,18, ,44,15

DRIVE GEARS 22:31,21:l32,19:34
1ST GEAR 3.321,3.592,3.985,4.220,4.955
OD O.838,O.759,0.821,0.854,O.954
VL COMMODORE
RB30 3.321,1.902,1.308,1,0.759,3.382REV
[USA 910]810/MAXIMA 3.321,2.044,1.408,1 ,0.752

Explaination of boxes
If the input gearset has a lower reduction, (closer to unity) then all the gears apart from the 1:1 direct coupled fourth will be taller. This means that 1st, 2nd & 3rd close up but fifth gets wider. This is probably the cheapest way to close up a gear set but it still has its problems. With a1:1 fifth this makes a good way of changing ratio spread reasonably easily.All 71B option 1:1 fifth boxes come with 22 drives 31 input sets so by changing to a 21 -32 set you can lower too tall ratios to give a ratio setin between option 1 and 2 etc. Eg option 2 with 22 31 gives 2.348,1.601,1.296, 1.138,1. By changing the input to 21 drives 32 this gives2.539,1.731,1.402, 1.231,1 (just like a taller option 1)

These are the common gearbox input ratios.
22:31
(The most common:- used in K 5 speed, 240Z 260Z, R30 & R31 Skyline, SR20,FJ20, CA20.) these are all FS5C71B boxes. From my understanding the codes mean F(rear wheel drive) S(overdrive) 5(five speeds) C(closer ratios)71(Main housing type) B(extension shaft & housing type). These boxes have typically 3.321, 2.077,1.308, 1, & 0.864 ratios. This is the most common box used in Nissan vehicles.

21:32
(K 4 speed and other under powered, commercial or heavier vehicles ( 720 orNavara utes, 280C, 280Z, R31-CA Pintara etc) For smaller engined or heavier bodied vehicles the above ratios were changed to 3.592, 2.057,1.361, 1, 0.852 by using the 21:32 input set. These ratios allow you to getof the line quicker with a heavy body that is under powered. This box is then known as a FS5W71B box. The W being for wider ratios. Most turbo boxes are the FS5C71B boxes with the naturally aspirated versions having the FS5W71B boxes. If you go to an importer they will often tell you a box is from a turbo or NA vehicle and often get it wrong. The easy way is to put the box in first and turn the input shaft counting the turns to produce one revolution of the output shaft. (3.3 turbo, 3.6 N/A).The main difference with early 5C turbo boxes is the use of heavier section countershaft (38mm diam) and gears. This means they change slower but can handle heaps more grunt. The earlier boxes (240K, 260Z etc) up to about 85 usually had a 29mm diameter countershaft. All boxes from 87 on seem to have the larger countershaft. 85 - 87 boxes can be a bit of a mixture of countershaft types.The best part of the FS5 (C or W ) 71B boxes is that once you have set up agood set of ratios, you can change the box from vehicle to vehicle by changing the bell housing. Eg an L series box to an RB 30, SR20, FJ20, CA(16 - 18 - 20), Z (18-20-22-24) by changing the bell housing.

23:28
(early Z and fairlady boxes these are not interchangeable with the 71Bfamily boxes)

18:32
Nissan Vanette and other commercials (if fitted into 5C gear set thisgives, 4.190, 2.4, 1.650, 1, 0.865 ( a good cliff climbing gearset?)

All information gathered from Errol Smith and Terry

If you can fill in any blanks then email me!!!!

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