Thread: Isuzu Gearboxes calculations ??

Looks about right. Why do you want to be doing 3000 rpm in 5th at 110km/h? 2000 sounds much better!

For 0.776 top gear with 1.003 high, 3.54 diff gears and 31" tyres I get 2042.03 rpm at 110 km/h.

Do not fit a 36D (Q) case. It will not last.

somewhere I found a reference that the max BP was developed at about 3200RPM.

Will my planned use of the Disco 1.211 LT230 be too high?

Originally Posted by Lotz-A-Landies

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Will my planned use of the Disco 1.211 LT230 be too high?

See my edit above. You do not want to fit an LT230Q (1.211) case. The ratio is good but they cannot hold up to an isuzu.


http://www.aulro.com/afvb/attachment...725_205509.jpg


However, a 1.222 would be fine. Despite what you have read, you do not want to sit on 3200 rpm on the highway.

Is it all the 211 boxes or just the "Q" suffix?

I feel that the 003 ratio will be too high for the 6x6.

Originally Posted by Lotz-A-Landies

Is it all the 211 boxes or just the "Q" suffix?

I feel that the 003 ratio will be too high for the 6x6.

All 1.211 are Q cases.

As I said, I would use a 1.222

Sorry I thought some of the 41 and 42 boxes were "T".

It all gets very confusing, the LT230 comes out of a pre-ABS Disco 1, so there is a possibility that it has a 28D 222, but wilh my luck it will be the Q.

Do we know when the D1 changed boxes/ratios, it had a 3.9 V8/R380 so I'm not hopeful.

Ignore max HP, pay attention to max torque....

An R series produces peak torque at 1400 Rpm and max HP at 2100.

Youd think that when you hit a hill it would sit at 2100 in third with a load on but they dont they creep down to 1400 Rpm and then just sit there.

or if youd like that in rice boy terms...

Hp lets you work out how fast you can hit the wall Torque tells you how far the wall is going to move when you do.

where ever peak torque is for your engine is where you want to get your desired cruising speed to be, you might want to even aim it a little higher so peak torque occurs just below your desired speed

As Dave and Ben have stated, be guided by where maximum torque is. Also, it is not a coincidence that minimum fuel consumption and maximum volumetric efficiency occur close to where maximum torque is made by diesel engines.

This pic (sorry not so clear) for a 4BD1 shows power, torque and specific fuel consumption. Maximum power at 3200 rpm as you said. Maximum torque at 1900 rpm, minimum SFC at 1400 rpm.

The same year (1989) 4BD1T has max power at 3000 rpm, maximum torque and minimum SFC at 2200 rpm