1970 C1600 International

A C1600 wont take bigger duals than 8.25........a few 4x4 s had bigger singles .,but needed special wheels.....I reckon fitting a C1500 axle would be easiest...4.33 ratio centre from a 1300 will fit the 1500 axle .

I've got an AB130 and the 240 petrol was pretty busy... like 50mph @ 3500 (redline?) with the original 4.88.

Finding a 4.3 diff center wasn't dreadfully easy in my experience. 4.88 are as common as muck... your mileage may vary

With 825x16 tyres, •85 Joey plus •82 5 speed overdrives it lopes along at 80km/h @ 1500rpm... the Perkins likes that.

I think 4.33 will be much too high for a 281

Att 55mph (90kmh)

8.25x20 2095rpm
9.00x20 1976rpm

Lang

Dodge 4 tonner had 5 stud wheels ,and pretty sure the diff ratio was 5.29.....might be easier to find.

I agree with John's comment that the 5.83 looks about perfect for the vehicle. The figures on the nearby ratios really don't do anything dramatic to change the situation (might give you a drop of 150-300 rpm flat out at best). Whether that justifies the expense and work of changeover is up to how keen you are of course.

The really high ratios out of the little trucks look great but there is no way a 281 is going to be drive-able with them, particularly with a load. You may find you can not even hold top gear on the flat in a very strong headwind.

Lang

One little catch ,the 1640 diff will likely have 6 stud wheels ,a 1600 has 5 stud.,so the front axle will need to be swapped too.

Here is some AT4 info you might like to compare it to.

Dodge 460 I was thinking of .....I ve used the centres in hyster forklifts .....the Dodge axle is for the 17" wheels that you cant get tyres for any more.,so the trucks are likely very cheap if 6cyl and a bit rusty.....Theres one down the road ,used to be a very nice truck ,ex Telecom orange and white,with the 245 motor .....However there is a decades old argument between father and son ,and the truck hasnt turned a wheel in years.

Yes John I was thinking along those lines too. Getting a bit complicated. Getting an RA - 187 would b the best I'm thinking

The two speed diff would take away that enormous gap between gears which can make them a chore to drive, needing to rev the bejeesus out of them before going up a gear.

Jarrod.