2.66 low gear vs close ratio
I think the Passon gears are rated to like 750hp or something. How high were the original 18 spline boxes rated to? If you're really pounding on a four speed in a race application, you're probably stepping up to a Jerico or Liberty anyway so all the arguments about how strong these things are seem moot too me. There are people that have raced those units though and they seem to hold up well, you don't read about guys breaking them.
For my truck application, it would be a great solution and cheaper than a GV. I'm not power shifting or drag racing. Most of the time my rpms barely crack 4,000 let alone 7,000. I imagine the trans would last as long as I am able to drive the thing. Plus, it will bolt right in with no mods except for cutting a hole in the floor to put the shifter in the right spot.
If I ever want to see any sort of mileage, I have to change the current 484/284 cam to something smaller which should also help torque across the board. Maybe some more rear gear too, like a 3.55 or a 3.73 if I can find one. I think it will be a great combo if I am able to work it out.
I'd be thrilled if I could knock down 16 mpg which is what my old Cherokee sport used to get.
Either you didn't read my earlier posts, about wide ratio boxes, and low rpm/hi torque engines, or you didn't understand it.
You have a 400 with a 284/484 cam. That can be a powerful engine, when it gets wound up. But doesn't take much of a mis-tune to make it mushy down low, early in the rev range.A well tuned fresh360-2bbl, can outpull a poorly tuned 400,possibly,like yours, to 3000 or maybe even,4000 rpm.
So,if you are operating your high-rpm engine in the 2000 to 4000 window,It is no wonder you are disappointed. And I will almost guarantee you that the Passon box will be no better than the A833 o/d, which is as good as the same as your NP. The splits are only a few % apart. Again, the 3.55s will help get it off the line, but after that,the splits will drag it down same as before, just a few mphs sooner. There is no getting around that. I've tried several different chunks with the od box, and the results were always the same.The splits are just too far apart with any cam just slightly larger than stock.
Like I said, you need a standard 4 speed with about 72% splits, or an auto.
Or like you said, drop that cam, like a hot potato.Put something in there that pulls right off idle, and take the granny outta the tranny, or swap it to the 833 od that you already own.
Since that's the most bang for the buck, that's what I would do; stock type short-period cam, and the 833od, a sharp tune,and 3.23s to 3.73s.
You will be smiling
