Overdrive or low rpm @ 100km/h (1 Viewer)

[GooSe77]

I have a H55 and 4:56 diffs and am searching for a nice solution to reduce rpmon the high way.
I'm not sure if I realy wan't to switch to 3.72 diffs or maybe only to 4.11 .... but getting unter 2000rpm would be sweet. I'm running 285/75r16 with should be 32-33" ....

At the moment I should be around 2500rpm ....

Is there a decent priced overdrive ?

Cons of using an overdrive ?

 

[clintnz]

Split case transfer case? Mark's Adapters do transfer case gears with a 44% lower low range, 8% higher high range. $$$$ though. Mine are very noisy too although mine are 55% lower low, 8% lower high range.

Cheers
Clint

 

[roscoFJ73]

4.11 diffs are the best all round solution. Which t/case do you have?

 

[GooSe77]

The tranny is the one from zhe HZJ75 with the H55F - don't no the name right now

4,11 gives me roundabout 2300rpm @ 100Km/h, 2800rpm @ 120Km/h
3,77 gives me roundabout 2100rpm @ 100Km/h, 2500rpm @ 120Km/h
the 8% gives me 0.98/1 and with the 3,77 it's 1950@100 and 2300@120

What's the downside of using the 3,77 ? Didn't all HJ61 come with that and wprked fine, even with 3,5 tonns ?

We use our toyo as daily drives and hollidays overlanding europe - so noise and fuel econnomy matter.
Can I take 10% less RPM = 10% less fuel ?

 

[roscoFJ73]

The ARL HZJ75 had the low ratio 2.296 transfer case.
It depends on what you want it for. The 4sp gearboxes often came with high ratio diffs to make up for a lack of 5th gear.
All the 60 series and 70 series in Australia had the 4.11(until the late 90s when the turbo engines came out in the 78/79 series). I'm not sure about the pre 84 60 series.
With 4.11 diffs you don't have to use 1st gear very often with the H55F.
Diffs gearboxes and t/cases ratios are something the dealer principle thinks will work in their market. In Australia its mainly what the mining, construction and agricultural industries want, at least in the low spec models.

Can I take 10% less RPM = 10% less fuel ?

In theory yes, in practice maybe a bit less. It depends on where your rpms will be on the torque curve, tyre size etc.