F series Diff info + Discussion

[Konakid]

Figured we have an S and T thread, the next most common is F series diff. A favourite for when people go turbo, want a bulletproof setup and are sick of smashing T series axles.

First of all some basic info about the F series Diff.

Crown Wheel: 7.5"

Braking: Drum and Disc variations

RA65 Celica = Drum
RT142 Corona IRS = Solid Disc
MA61 Supra = Vented disc
MX73 Cressida = Vented Disc
YR22 Tarago = Drum
MS112 Crown = Drum
Corona Mk2 = Drum

RT142 live axle borgwarner discs can be adopted (semi) easily onto some F and T diffs, more info here:



F series ratio info here on Toymods too.



To see which ratio your F diff is check out this:

Read the Axle Code from the vehicle indentification plate.

first digit: ring gear diameter

A 138mm
B 145mm
C 6.25"
D 6.62"
E 7.1"
F 7.5"
G 8"
H 9"
J 9.25"
K 9.5"
L 10.5"
M 12.5"
N 13.5"
P 14"
Q 12"
R 162mm
S 6.38"
T 6.7"
U 6"
V 10.6"
W 15.5"
X 142mm
Y 158mm
Z 202mm
- no ring gear = FWD

Second, third digits: gear ratio

01 3.30
02 3.36
03 3.545
04 3.556
05 3.70
06 3.889
07 3.90
08 4.111
09 4.222
10 4.375
11 4.444
12 4.625
13 4.79
14 4.875
15 5.125
16 5.286
17 5.60
18 5.714
19 5.833
20 6.167
21 6.667
22 6.78
23 6.833
24 7.64
25 4.556
26 5.571
27 3.364
28 4.30
29 4.10
30 3.727
31 3.909
32 6.591 or 4.807
33 7.503 or 5.583
34 6.781 or 4.786
35 7.636 or 5.60
36 4.778
37 3.583
38 3.417
39 3.154
40 5.375
41 3.308
42 6.500
43 3.550
44 3.214
45 3.533
46 2.928
47 3.944
48 3.356
49 3.729
50 3.400
51 3.736
52 3.722
53 3.250
54 3.941
55 3.333
56 2.821
57 4.058
58 3.238
59 3.234
60 3.519
61 2.724
62 2.892
63 2.655
64 4.312
65 3.837
66 3.071
67 3.526
68 3.095
69 4.176
70 5.857
71 2.962
72 3.949
73 4.285

Fourth digit: no of pinions, ltd slip-yes/no

Code pinions ls
2 2 no
3 2 yes
4 4 no
5 4 yes



Example: F372 = 7.5" 3.58 final ratio 2 pinion diff. Will not be stamped on the diff, you will have to check the build plate on the firewall of the car you pull it from.


LSD Availability: Altezza LSD's form the likes of Kaaz etc will bolt in but a spacer ring needs to be made up for it to work. Can anyone shed more light on this? Steroidchickens?

Tomei Altezza centre into an MS112 Crown = Works, no problem!
Cusco Altezza centre into YR22 Tarago = Success!

IRS centres will bolt straight into Live axle F diffs so you could use an MA61 LSD but apparently no good for proper driving with small clutch plates and small surface area they aren't very effective and usually well worn out. An aftermarket 1.5 or 2 way or locker is your best bet for grip or drift work. See Kaaz, Tomei, OS Giken, Cusco, (TRD no longer available)

Side note for celica/cressida/irs corona - Altezza/RS2000 Cusco LSD was a nightmare for my diff guy into RT142/RA65 IRS centre probably due to the car not being LSD to begin with. Machining and lots of hunting for correct bearings needed. Have been told (but can't confirm) that the MA61 diff centre half shafts are needed as they were lsd from factory and are shorter to suit.

Torsen and Truetracs LSD's are also available. Many hilux 4wd live axle ran 7.5" FRONT diffs too 80 and 90's, possibly 2000's. Lots of options from 4 wheel drive aftermarket companies.



Cars:

MX13 Cessida - 3.9 - 1410mm (Same width as T series/S series/KE70 BW)

Tarago YR22 - 4.1 manual and 4.3 auto - 1435mm
Uses a G series (Hilux) diff nose flange bolt pattern (60x60mm) All other F series is 55x55mm)


Crowns:

MS110 Solid Axle (coils) F362: 7.5", 4.77:1, 2 pinions, Open
5x114.3 1450mm Solid disc

MS112 Solid Axle (coils) F292: 7.5", 4.10:1, 2 pinions, Open
5x114.3 1450mm Solid disc

MS123 Semi trailing arm IRS F285: 7.5", 4.30:1, 4 pinions,
Clutch LSD 5x114.3 N/A Ventilated disc, 1 piston calipers

MS50 Solid Axle (leaf) F292: 7.5", 4.10:1, 2 pinions, Open
5x114.3 unknown Drum

[biggo]

If you have an IRS setup, you will need a center that has circlip grooves.

IRS has shim adjustment = pay diff shop to set it up

80 series landcruisers and hiluxs of that era have F series FRONT DIFFS, usually with ratios like 4.1/4.3

[Slimer86]

Kona I will be fitting an Altezza torsen in the coming weeks, and will let you know how I go and any difficulties.
another question, I assume that the diff backlash is adjusted to the same specs as a T-series?
I have ST141 rona rear brakes to put onto it. Will post up any difficulties I have with that.

[steroidchickens]

mark 2 F series has no oil baffles. i learnt this the hard way at eastern creek when i killed a centre.

tarago F series come standard with baffles.

will be installing altezza TRD 2 way next month will put up info then.
first trd 2 way i had ant put together.

[driftke70]

you rekon its worth putting baffles in
can just overfill the diff oil?

[steroidchickens]

really need baffles.

i made some up. was easy as.
even with baffles i extended the breather an inch and still overfilled diff oil.
after that it was fine.

[OMG866]

Just a question about the ''Tarago YR22 - 4.1 and 4.3 - 1435mm''
would the 4.3 be the auto or manual?

[Golberg]

Auto my friend.

[steroidchickens]

4.3 auto 4.1 manual

[OMG866]

Cheers Golberg and steroid. hopefully getting one this weekend. pritty keen to see how your Lsd goes steroidchickens. Just lookin to go in the same direction