New member from Oz..

[AussieXLT]

Thanks for the add - I have a ‘76 F100 390 (trailer pack) that I’ve owned for about 7 years now have done about 17,000 miles in that time.
No major changes, wiring was a birds nest and it started smoking from under the dash one day early on so I bought and installed a full American autowire kit which fixed a lot of issues the truck had.
Only other change has been a lowering kit and new Gabriel shocks absorbers installed a couple of years ago - 4” down at the front and 2” down at the rear, not a huge fan of the rake look but I’m happy with it.
First question is did the trailer pack have stock ratios in the rear diff or different for towing? Is there a reference with the ratios set out - I’m assuming of course that mine still has the original ratios in it, I do a lot of highway driving and was hoping to swap in a more economical ratio.
Cheers
JD

[cep62]

Welcome from Michigan.
My Dad was stationed in Australia during WW II.
He was with the U S Airforce as a Bomber mechanic.
He had fond memories of the area.
On our home page there's a lot of factory literature . This might be a link.?

http://www.fordification.com/library/in ... ategory/20
You should have a inch axle with 31 spline shafts . those are fairly easy to swap out gears.
If there's no tag you can check the gear ratio by jacking it up spinning the drive shaft and counting the revolutions and doing some math.