Thread: Series Gearbox

How do you Find the High Gear Transfer Box, Colin ?
Do I put the Ashcroft one I have in Gilbert ????
Or STD with the Fairey overdrive.
Thanks

whitehillbilly

I think Colin has the high ratio box with the Isuzu engine, so his experience is not really relevant.

My experience has been that while the higher ratio may be useful for a swb, I would not bother for a lwb with the four cylinder engine. I have an overdrive on my lwb, but I rarely use it. Two reasons for this - it is noisy, and the four does not have sufficient power to pull the higher mass with overdrive except on dead flat ground.

I would also question the need for higher gearing. Running 7.50 tyres the 2.25 engine is quite happy at the vehicle's maximum speed (around 110kph), and the engine noise is way below other (mostly wind since I replaced the bar treads) noise. I can see where it would be useful if you had a swb running on 6.00 tyres, and certainly if you have a different engine (such as Holden) that is less than happy at high rpm.

Having experience with the overdrive, I agree that if you need a higher gearing, the high ratio box is definitely superior to the overdrive, and the use of high ratio diffs. The only advantage of the overdrive is the ability to split gears, plus I find it a slight advantage where I need to drive in low range,but come to a short stretch where I can go faster than is feasible in 4L - a lot easier to change in and then out of overdrive than to change transfer ratios on the move. The main advantage of higher ratio diffs is how easy and cheap it is to convert (unless you have a salisbury rear), but then you have the speedo issue.

If you want to use your Series Land Rover for outback trips, there is always a chance that someone other than you has to work on your car. I'd use only parts that any mechanic can look up in a L/R parts or optional equipment catalogue.
.W.

Thanks.
So, my Fairey thats in good condition would be the better option ???? On My SWB.
Yes standard parts Is a good thought.

whitehillbilly

These are the essential parts you need to get you going again after you've removed your overdrive. Strictly speaking you don't even need a new nut. I carry these parts with me at all times..W.

Originally Posted by JDNSW

I think Colin has the high ratio box with the Isuzu engine, so his experience is not really relevant.

The power output of the 2.4 NA Isuzu isn't far off that of the Land Rover diesel.
When building up the vehicle I had warnings that it would be over-geared but this didn't prove to be the case.

As for carrying standard parts.....there is one gear in the high ratio transfer box which is unique to the conversion and of course the modified case.

In a 60kph zone it doesn't really like top gear, seems happier in 3rd but otherwise it has much 'longer legs' that my Series I. Easily holds 100kph on the freeway but does slow a bit on long inclines. If I had the standard ratio it wouldn't go as fast but I might be able to hold the speed better on hills.

Colin

Not so much the power output, but the rev range at which the engine is comfortable, and, probably necessary on low powered vehicles such as we are discussing, geared so that maximum power is developed at about the maximum speed the vehicle will comfortably go. Too low geared, you run out of revs before reaching the speed you could travel if lower geared, too high geared, you reach maximum speed before the engine reaches maximum power.

Much less of an issue with higher powered vehicles, where the maximum speed is well above a sensible speed for the vehicle anyway, and it is an advantage in a number of respects to have the gearing high enough that the engine produces the power needed to travel at a sensible speed with the engine well below maximum power revs.

Of course there are other aspects to it as well, like having the gearing low enough that you can drive in top gear at 50kph, as this is the most common speed limit for urban driving - my Isuzu County only barely meets this criterion.

Also, if you have lots of gears, the overall ratio is much less important - but with the Series we only have four in each range.

Originally Posted by JDNSW

Not so much the power output, but the rev range at which the engine is comfortable, and, probably necessary on low powered vehicles such as we are discussing, geared so that maximum power is developed at about the maximum speed the vehicle will comfortably go. Too low geared, you run out of revs before reaching the speed you could travel if lower geared, too high geared, you reach maximum speed before the engine reaches maximum power.

John, I understand your points but a lot of UK users fit the High Speed Transfer Box without issue.
The only info I could find on AULRO mainly related to Holden conversions High Speed Series Transfer Case

Overdrives are known to be fragile & often noisy. Changing the diff ratio also affects low range gearing. The HSTB raises the high range ratio but barely affects the low speed ratio.

Article here mentions the potential difficulty pulling away on a steep slope and sometimes needing a gear ratio between 3rd & 4th.
Ashcroft Transfer Kit

Happy with the ratio in Wallit (my C240 powered SIII) but I guess it's a compromise between a reasonable road speed, noise, economy and usability.

Colin