can anyone help me with the box to run?
the engine is a single port 1600 (ratio rockers fitted very soon)
the problem is the car seems to struggle on a few highway hills. with the stock box
the tyres i run are 265/75 15 road patern
so in other words what swing axle box has the shortest 4th gear

thanks

do you have four (1970s) or five stud (1960s) wheels?

its a 70 model four stud ie(70BAJA)

The far better option would be to put a 1600 twin port in there, maybe some slightly bigger pistons too. Then you'll be able to pull the tall 4th gear.

I'd rather spend the money on more power to take advantage of the nice tall highway gearing than to spend the money to put in an older model gearbox with short gearing.

I'm with wes. By the time you put in the early box in a reasonable nic you could just as easily put on a set of 1640 pistons and pots to go with your ratio rockers. Besides, a stock 1600 will destroy some early swingaxle boxes so it's a short term gain anyway.

thanks guys ill save some bucks and put some larger pots in
hopefully the ratios make a difference

Well, to answer you original question, a 1200 barrel box. (4.3 diff. and 0.89:1 4th gear)
Available at most rubbish tips and bush dumps!!!
L8tr
E

closely follwed by a late 1300 box (1971-73?) cos it has a 4.3 diff too, with four-stud wheels. Do you need tyres that big?

265/75 15 i have are roughly an inch smaller than 31 10.5Rs
i do believe that most bajas around are running the 31s
so to answere the question do i need them that big
their not that big

correct, they are not that big. I run 31's and used to have a 3.88:1 R&P box, it was good. The smallest engine I ran with that box was a 1776. It had enough power to pull top gear, and was nice on the highway. I drove my baja with that box and a 1915 from brisbane to canberra and back for the summernats one year. It was good.