Specing an older truck for B-train

what speeds are you trying to go and how long are the trips? In general, a higher number rear end will give you a lower first gear to help you get off the line, but also a lower top speed. If nto driving to far its not a big deal.

 

400 is pretty light for a super b. I've used a 425 cat a few times, and even that's a struggle to get it up to highway speeds. But it does work. I think that with the old 400 though you might be a bit of a speed bump. These Alberta highways have gotten crazy the last few years with the volume of both heavy and light traffic, and it all seems to want to do 110km +. I pull super b with close to 600 hp and I've often got a convoy behind me. I don't think going to an 18 is going to make that big a difference, you just don't have the power there for 8 axles. I'd look for something with more power. Just my thoughts!

 

I agree with lowmax unless engine is tweaked a bit I think you would be stuck doing 90 km/h or less on a windy day fully loaded in winter .. The one I drove a few weeks ,back in the late 90's took a long time to get going with a tridem in winter when the wind was strong .. 15 speed will be good In the fields due to low gear reduction but you will miss the splits of a 18 in the higher gears with small power PS you may want to ask in the Canadian forum. More people would be familiar with the weights you will be pulling and have gearing suggestions

 

You do want to check with the Highway patrol or the licencing guys to find out if there is a HP requirement for a "B" train, 400 is not legal in our area, B.C. and Alberta

 

it could probably be done with a 400 and gears in the 4.10-4.33 range. esp with being short haul and slow speed. if you could bump the hp up to better than 450 preferably more in the 500+ range i think you would be happier though.

 

Yes the low flow issues will be worse if you added power, my opinion would be to convert to high flow and then find a radiator and air to air from a truck that had a cat in it, you will then be able to also convert the engine to air to air and that will help with power.

Depending on the CPL it should be fairly easy to get the power but most likely won't be cheap as most likely that engine has STC injectors.

Ideal gearing would put your cruise rpm between 16-1700 with a big cam and you cannot be afraid to use the rpm of the engine to get up to speed.

 

A couple final thoughts, if you start doing all these changes, inc. changing diff ratios, it's going to be a money pit. There are way too many newer used trucks out there for sale fairly cheap that make good farm trucks, with enough power. But, if you want to do it as sort of a hobby/project truck, and don't mind a few thousand here and a few thousand there, that's up to you. The other thing, is that in the 20-25 years since b trains started, the traffic volume has probably almost doubled. I remember being able to drive from edmonton to calgary with high beams on much of the time because there was no oncoming. (Well, ok that was in the 70's lol). But things to consider anyhow.