Thread: LT95 T/F ratios Stg1/110/Isuzu

Originally Posted by Lotz-A-Landies

Sorry Ben

I read 1:1 + 4.7 diffs making a final drive of 4.7 so I guess you you mean the RRc LT95 ratio of 1.12:1 + 4.7 making 5.26:1 final drive.

What I'm concerned about is with a low revving engine like the 4BD1T that develops max torque at about 1800RPM and (Def t/f) 4.99:1 final drive it will be well above the torque curve at 3368RPM doing the basic highway speed of 100KPH in 4th and still well above the curve at 2678RPM in 5th

With the D1 ratio of 1.211 I'd be doing 2893 RPM in 4th and 2300 in 5th, or at least that's what I'm hoping. The other issue is that the Perentie 6X6 with it's wider track, full ROPS cab, double chassis and leaf springs is probably quite a bit heaver than my regular width, dual cab, coil sprung defender.

Diana

Perentie 6x6 are 1.113:1 x 4.7 = 5.231:1 in 4th.

I sense some deja vu here:
http://www.aulro.com/afvb/isuzu-land...-perentie.html

I guess it all comes down to how heavy you will be and how much towing and/or hill starts you want to do. i.e. I suspect your limiting factor will be the tall 1st gear of landie gearboxes coupled with your tall diff ratios, rather than getting optimal highway revs. With a turbo the torque peak is irrelevant as in 4th or 5th mine will keep pulling hard all the way to the governor.

Originally Posted by isuzurover

Perentie 6x6 are 1.113:1 x 4.7 = 5.231:1 in 4th. <Yes maybe, but I'm not using an LT95 so my choices are different - ever seen a V8 90 or a 2.5litre 90 LT230 lying around in this country?>

I sense some deja vu here:
http://www.aulro.com/afvb/isuzu-land...-perentie.html <Sorry, can't see the bit with the Isuzu LT230 - LT85 ratio?>

I guess it all comes down to how heavy you will be and how much towing and/or hill starts you want to do. i.e. I suspect your limiting factor will be the tall 1st gear of landie gearboxes coupled with your tall diff ratios, rather than getting optimal highway revs. With a turbo the torque peak is irrelevant as in 4th or 5th mine will keep pulling hard all the way to the governor.

The reality is that all LT230 have the same low ratio irrespective of the high ratio fitted, so if hi ratio is too tall, then you use low.

My issue is that the through drive on the middle axle is in a modified Rover style diff and I'm not currently contemplating changing it's ratio, so my compromises will have to be using available LT230 ratios and therefore the Defender 110/130 4.99:1 or Disco 4.29:1 overall ratios are my logical choices.

Originally Posted by Lotz-A-Landies

The reality is that all LT230 have the same low ratio irrespective of the high ratio fitted.

My issue is that my through drive on the middle axle is in a Rover style diff and I'm not currently contemplating changing it's ratio, so my comprimises will have to be using available LT230 ratios and therefore the Defender 110/130 4.99:1 or Disco 4.29:1 ratios are my logical choices.

My point is that with 3.54 diffs and a LR 5-speed box I think you will need a 1.41:1 t-case unless you want to do hill starts in low range when heavily loaded or towing.

Originally Posted by isuzurover

My point is that with 3.54 diffs and a LR 5-speed box I think you will need a 1.41:1 t-case unless you want to do hill starts in low range when heavily loaded or towing.

And yes, you may be correct, I have two 1.41 ratio LT230 boxes, but would still like to try with the 1.211 ratio box first.

A bit like you played around with ratios on yours.

(BTW one reason not mentioned above, is that I want to use one of the 1.41 ratio LT230 boxes behind the Ashcroft short bellhousing R380, on my SIIB.)

PS - the drop sides on the ICR trayback for this Defender have the same sticker you use for your avatar!

depending on what you're putting on the back

if you've got the 3.5s in the back Id be going the 1.41 tcase

if you have 4.11 or 4.7s you'll get away with the 1.21 tcase

Originally Posted by Blknight.aus

depending on what you're putting on the back

if you've got the 3.5s in the back Id be going the 1.41 tcase

if you have 4.11 or 4.7s you'll get away with the 1.21 tcase

My 110 Australian supplement handbook gives the following-

3.9 Diesel LT95 0.996:1

LT85 1.003:1

V8 Petrol LT95 1.336:1
LT85 1.410:1

I have drawn a gear split chart for 3.9 diesels using either gearbox. I will see if they scan and post them.

I have a civilian 6x6, which runs 4 speed box. Has been fitted with 3.5 diffs, 31'' tyres. Using the GPS at 100ks it is doing 2,900 rpm & will pull quite well from 1,800 in top. I would not like 1st to be any higher. Hope this helps. Paul