CROWN & PINION GEARS!

[G-MAN]

Anyone know where i can get a set of crown & pinion gears that will suit 37 inch tyres.

[Saltman]

Jeeez, just thought you had stripped a Patrol diff (not too often you hear about such an achievement) ... then I read the 37" tyre bit.

OK, to answer your question: Australia ?

[G-MAN]

You had me all excited! Then you said Australia

[G-MAN]

Any one know how to work out, diff ratio to wheel size? Wanna run 37 inch and what diff ratio would bring it back to standard.

[Gerrit Loubser]

Hi G-MAN,

Your 4.8 GRX Auto came with a final drive ratio of 3.545:1 and 275/65R17 tyres as standard, if I am not mistaken.

The tyre nomenclature works as follows:
275: Nominal tyre section width in mm
65: Aspect ratio in % (the ratio between the height of the sidewall and the section width
R: Radial tyre construction
17: Nominal rim diameter in inches

The nominal diameter of your standard tyres (in inches) can be calculated as follows:
1) Calculate the height of the sidewall (in mm) by multiplying the section width by the aspect ratio (265mm x 65% = 178.75mm)
2) Calculate the height of the sidewall (in inches) by dividing the answer from 1) by 25.4 (178.75 / 25.4 = 7.037")
3) Calculate the nominal diameter by adding twice the sidewall height to the nominal rim diameter (2 x 7.037" + 17" = 31.075")

Now if you want to fit 37" tyres instead of the standard tyres, the gearing will become higher in the ratio of the tyre diameters. To compensate using final drive gearing, you will have to multiply the final drive reduction ratio by 37 / 31.075 = 1.191. Seeing as your current final drive ratio is 3.545:1, you will need a final drive ratio of 4.221:1.

Now as far as I know, the 4.8 GL manual comes with a final drive ratio of 4.375:1, so this might be an option. This will yield gearing that is 3.65% lower than standard.

The older manual 4.5 had a final drive ratio of 4.111:1, so if this ratio is used, you will have gearing that is 2.6% higher than standard.

I am not sure how interchangeable all these crown wheel and pinion sets are, so you will have to do some homework, but this should help to narrow things down a little.

One other point to note is that two different basic differential designs are used in the Y61 Patrol, namely the H233B and H260. The numbers refer to the diameter of the crown wheel in mm and in general the larger the crown wheel is, the stronger the diff. All the Y61s use a two-pinion version of the H233B diff in the front axle and all rear diffs are four-pinion, but only manual transmission 4.5s and the 4.8s, use the H260 rear diff. Patrols with the TD42 or ZD30DDTi motors have the same 4.111:1 ratio as the 4.5, but these have the H233B rear diff.

[G-MAN]

GERRIT jy is n guru op alles! Dankie .

[Sickness]

Normally every 2' above standard up on gear ratio.Like 4.1 33s ,4.56 35s, 4.88 38's.So for you up two ,whatever they are.4.3/4.1

[Engel]

I also want to change my gearing but the costs is astronomical. I have a 260 diff at the back [used to be 233] but lost ground clearance. Its ok on 33" but runs out of power on serious hills. So before i go 35" I must do the final drive change [or crawler gears]

[G-MAN]

Thanks Jared.

[jakeslouw]

The MQ has the C200 front diff?
What will a set of 4.11 gears cost for that diff? Can I find a diff with that ratio in South Africa?