My slow ACCO

Swishy, I am hoping I have a common diff ratio, my truck started life as a petrol tipper 4 speed. It was upgraded and stretched (as the story went in the ACC mag) to a Perkins 5 speed and quicker diff, carting Apples to Melbourne market from Harcourt. A set of 10.00 tyres are on the gunna list.

I am trying to find a load of gumboots and brollies to sell the thongs and shorts brigade from the west..... they won't cope with the cold and rain.

Sarge :-X

Hi Bono,

You'll find what the factory diff specs on the plate in the door frame on the passenger side of your ACCO.

On my 1830/B it says:

IH Model IH Code Axle Model
RA-186 14186 17202

ratio: 6.14/8.38

When I got the truck top speed was 90kh/m at 2850 max rpm.

Because I mostly do a short highway run to our farm (and the turbo perkins is slighty more powerful than the orignal Neuss it replaced) I decided to replace the diff centre to a 4.88 which my calcs suggest also got the low range down to 6.65.

It was definitely the right move for me.

Top speed at max revs with a good wind up my arse is now 110km/h (I love overtaking modern speed limited trucks!) But generally it will cruise at 100-105km/h and between 90-95km fully loaded without using full revs anymore.

Slightly better full economy and hopefully longer engine life.

A word of warning if you are contemplating a change though:

• a different ratio doesn't necessarily mean more speed unless your motor has got the required torque and power. It might mean the same speed but less revs which is probably what you're after anyway. I personally wouldn't bother if you are doing mostly short urban runs.

• tailshafts have different splines and joints so don't necessarily expect it to bolt straight to your new diff or centre.

• If you're changing the whole diff complete make sure your braking system is the same, wedge brake and S-cam systems don't necessarily marry that easily.

Just my advice, I did a fair bit of homework on this before I did anything and it was well worth it.
Cheers,
Joe

Well folks, I might be a bit like Ernie who drove the fasted milkcart in the west.

I have done the maths backwards to come up with a dif ratio of about 5.4...... I am doing 60mph at a shade over 2500 rpm which I called 2600 for the sums and on 9.00 tyres which I assume have a radius of 21. all based on Swishy's book posting.

From other advice I have recieved, if I was crazy enough to abuse an old lady, I could get along a little faster. I calcluated maybe 65 mph at 2800 rpm

I dont need that sort of grief

sarge :-X

GuddayM8

Dont like 2 B a party pooper

But

a 1000 x 20 tyre = 10" of rubber 20" of rim & 10" of rubber bout 40" diameter
A 900 x 20 = 9" & 20"& 9" = 38" diameter
A 1000x20 has radius of 19.6" to 19.9"
A 900X20 Has radius of 19.0" to 19.2" depending on treads Hwy or Off Hwy

ButEyeDoSt&2BCorrected

So U might Have 2 Rehash them figures again

cya

[ch9787]

on my old acco 1830B with a turbo neuss 358 motor was running the same 6.14 ratio (high ratio of the 2 speed diff) was topping out at 90km/h ..since i done a lot of interstate trips i changed the centre to something that was topping out at a little over 100km/h ..it wasnt much of a difference but it is nice to cruise along with other highway traffic .. i did have a old acco that had a perkins phaser 6cyl retro fitted ..with a overdrive 5 speed box & highway 2 speed diff centre ..it topped out at 127km/h and would hold top gear on many hills

Hey Swishy that would be the police training coming out in sarges calculations
just added a couple of extra numbers on the actual reading

Pete

I dont know about the tyre size number, the radius figure I took from your book swishy, but all that aside, 25 to 2600 revs and the little arm thingy on the speedo is firm on 60 mph, clearly visible just past my white knuckles.

as for holding 60 on the hills, that would be the DOWN side of the hills for me Kenny...

Sarge :-X

Gday Sarge,
Dont put too much faith in that speedo, more likely to be reading slow.
Cheers Pete