Auxiliary transmission or 13 speed? Question for old timers, err experienced drivers!

what are you building and what do you want to pull with it?

 

18 speed and a rear axle ratio that you can put the peak torque on the leading edge of the speed you want.

 

At that gross a Spicer 6 speed should be plenty. With 3:90 rears will move 33,000 just fine. The issue you will have with fitting a 9,10,13,or18 speed behind a small engine in medium duty truck is going to be finding the right sae size bell housing. Find one and no problem.
The other issue you will have with a brownie is you may not have the horsepower in a smaller engine to turn it at higher speeds. Meaning when you get up into the last couple gears on the brownie it may bring the rpms down way to far for the little engine to pull making those gears useless. Those smaller engines have to stay up around 2400 rpm all day long to work.

 

When I worked at Pepsi we had a ton of these. The smaller single axle trucks all had a 6 speed, the bigger tandem axle trucks had 10 speeds in them. I can’t recall if they were the 360’s or the 466’s. All of them would get down the road just fine at the speed limit as long as you kept them wound up good.

 

The 4700's had automatics or 5 speed manual with a 2 speed rear end.The manual and 2 speed rear end gave you 10 gears to work with.Id go with the factory set up,5 manual and 2 speed rear.

 

The 8 speeds + single low (no back reduction box) were more common in the smaller trucks then the 13s, we have a 330 Pete single axle with a 3126 that may or may not get overloaded on occasion with hay and machines on the tag and it’s low enough to get going and geared short enough to pull through the top gears. Better then the 2 speed rears

 

The reason they made brownie boxes to begin with was because they didn't understand how to to make all of that in the transmission itself. Basically the 13 speed or even 10 speed replaced the need to have the brownie box.

Once you have the truck you want, you have to look how the axle is geared. I have one F-350 that has a 308 or 358 rear, and with the direct transmission I have no problem cruising 75-80. I have another F-350 that has a super towing package that has a 411 rear in it that is geared much lower, but that one has an overdrive transmission.

If I were you I would try to match the gearing of your rear to your transmission. I think that's an easier task and if you put the brownie in you have to have the Drive Lines exactly correct which you'll still have to check if you're putting a larger transmission in, but I think it's a little more complicated with the brownie box. Plus you have to install the linkages and shifter. And make a mount.

The dt360 I believe should come with an industrial SAE flywheel housing. If it does not you can get one that you can put a regular Road Ranger transmission if you would like. Depending what truck you get you may or may not have to trim the floor or the firewall, however I think the International Trucks it may fit. I'm not talking about the full size Road Ranger I'm talking about the small Road Ranger.

They're not cheap but there are small roadranger transmissions, RTO 610 for example. They also make a 13-speed. These were baby Road Ranger transmissions they usually went behind 3208 or some lighter horsepower engine like the dt360. Most of them were not overdrive but there are kits available you can change them over.

If it were me I would look for a truck that had a two-speed rear. I would get a 6-speed transmission Fuller. They're smaller and lighter then the 10-speed or 13 speed, and the two speed will give you what you need.

Those trucks (6 speed) ran with a single speed rear so if you have one with a two-speed you can really split the heck out of it.
At that point you'll be able to pull anything.

I think that's what I would look for. That's the easiest and simplest situation but you still have to match the rear to transmission for cruising RPM.

 

Actually you could get a 10 speed twin countershaft Spicer in a 4700 in the 90's early 2000's. It's a tight fit and I would not recommend. But they came from factory.