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aussie 4 speeds....difference in 2nd gear?


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#1 lcgtr1970

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Posted 13 February 2017 - 11:02 AM

hi all

I have an aussie 4 speed in my lc, and I also have an aussie 4 speed in an hz wagon.....both are 6 cyl motors..... now I have noticed that in the wagon 2nd gear seems quite useless. It seems to be quite short in ratio and I find I am changing to 3rd very quickly. Whereas the 4 speed in the torana, 2nd gear is great...it seems to be a good progression to third and allows me to rev right thru and actually 'use' 2nd gear.....if that makes sense.

So my question is, are there different ratios of 2nd gear in these things? And why?

cheers



#2 Bigfella237

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Posted 13 February 2017 - 11:52 AM

There were 5 different ratios sets (that I know of) available in the Aussie four speeds, the three most common are:

 

M20 (most common 6 & 8 cylinder)

1st 3.05

2nd 2.19

3rd 1.51

4th 1.00

 

M21 (typically used behind 308 V8)

1st 2.54

2nd 1.83

3rd 1.38

4th 1.00

 

M22 (used in one-tonner ie. "stump puller" first gear)

1st 3.74

2nd 2.68

3rd 1.68

4th 1.00

 

The other two were specialty ratio sets used in XU-1 and L34 options only.

 

Contrary to popular belief, there is no strength difference between these boxes, other than the difference made by the ratios themselves (a higher ratio means less multiplication meaning it will handle more input torque).

 

I have no idea what variants you may have in either car, the wagon is most likely an M20, maybe the LC isn't, who knows?

 

The other difference is probably in the final drive ratios (including tyre diameter), taller ratios tend to make gears feel like they have "longer legs", whereas lower ratios will see you changing gears sooner.



#3 yel327

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Posted 13 February 2017 - 12:02 PM

As above, although the wide ratio M20 (later called M22) was the 6cyl 4spd in HQ commercials.

M21 has a higher torque rating than the others, but if it is true then it can only be by the meshed tooth count between the clutch gear and the cluster. Otherwise everything looks identical.

#4 lcgtr1970

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Posted 13 February 2017 - 02:23 PM

thanks for that info guys. Is there anywhere I can look for any numbers which may suggest what type of ratio it is? I have another 6cyl 4 speed on my bench.



#5 yel327

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Posted 13 February 2017 - 05:27 PM

Just remove the side cover and look for numbers on the cluster gear. Original units will have a part number stamped into them, aftermarket generally only have 3 x digits (the last 3 digits of the genuine number).



#6 piquet

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Posted 13 February 2017 - 07:53 PM

Plus XU1 box ratios of in the later LC and LJ

1st     2.54

2nd   1.83

3rd    1.25

4th    1.00



#7 yel327

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Posted 14 February 2017 - 04:50 AM

^^Andrew mentioned the XU1 in his 4th last line. There is the optional close ratio XU1 as well that L34 had too also mentioned.






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