The bus has a stupid tall rear gear. Two of them in fact. High range is a 5.38:1, low range is a 8.11:1. With a 4 speed, it will pull the world...slowly.
I'm wondering if anyone knows of a truck 5 speed OD transmission that will bolt up to the FE big block.
Thanks.
https://www.holley.com/search/?q=fe%20BELLHOUSING
Could you fit some bigger tires under there? At least in the rear. Idk if it would end up being more expensive than a different trans or not but hey at least it's easy to do!
In reply to RossD:
I happen to have a T56, I wonder if it would handle the abuse of a 15K pound bus.
You can adapt a Dodge nv4500 to work behind it. Here is a link to the article I used a few years ago. It has the advance Adaptors part number in there. You will have to fab a trans mount. http://www.ford-trucks.com/articles/installing-the-nv4500-overdrive-transmission/
Figure out the gearing, maybe the t56 is perfect with that long 5th and 6th or maybe you couldn't ever use either and it's better to sell to fun a better trans. Pretty much do some calculations, I think a t56 maybe a little too close ratio for a bus but hey, you never know until you research.
Peeve: That's short, not tall 
Gear Vendors overdrive unit?
You've got miles of driveshaft under there, shorten it up with a 2 or 3 speed aux trans. Twin sticks are always fun.
Can you split shift with that rear end or is it an on/off thing?
In reply to Knurled:
Dangit I always get it backwards! I think long gears like take a long time to run though them (highway gears)
Wait I said 5th and 6th are long, they are short??? 0.5 iirc for 6th
Put another transmission inline backwards. 4:1 first gear is .25:1 overdrive 
Toyman01 wrote: In reply to RossD: I happen to have a T56, I wonder if it would handle the abuse of a 15K pound bus.
Probably not. Weight of your bus would probably limit its lifespan.
This is from Tremecs site: Our T-56 Magnum 6-speed is rated to accept as much as 700-lb. ft. of sustained torque in a vehicle weighing as much as 4,500 lbs.
Do you want to keep it manual or auto? The NV4500 is a good possibility, not sure about being behind a Ford. One of the Ford ZF5/6 speeds is possibly a good option. A remote aux transmission is another good idea.
NV4500 or ZF6 would be my picks, provided you can adapt one of them to an FE.
Or, go for a medium duty truck trans with OD...
It is upshifts under load that will kill the transmission. I would not suggest a pickup transmission. Picture yourself on a hot summer day with the family aboard pulling a boat or something up a steep grade.....engine laboring in a low gear.....hill levels off a bit.....rev it till the valves float.....quickly grab a gear and pop the clutch as you loose momentum....and.... BANG!
Why don't you look at regearing the axle or replacing it with something more appropriate? Easier to switch out an axle or some gears than to start playing with adaptors anyway.
mazdeuce wrote: Can you split shift with that rear end or is it an on/off thing?
The rear axle can be split shift. I have been shifting 1-4 in low range and then shifting the rear to high.
An auxiliary transmission is a thought, but those things get rather expensive as does the NV4500. I'll have to keep a lookout for something. I wonder how long a E4OD would last in a bus.
I just did a little math. Assuming the tires on the bus are 11R22.5 and top gear in the trans is 1:1, you should only be turning ~2600 rpm at 60 mph with the rear end in high (5.38). That makes me think that provided you're staying with gas power, there's no need to re-gear or swap transmissions at this point.
What is the diameter of the tires? To be honest, a 5.38 doesn't not sound like a very low gear for this application.
IMHO, leave everything as-is until you can figure out the engine choices. IF the engine bay is large enough, 12V Cummins 2WD Dodges tend to sell for reasonable money.
I would look at medium/heavy duty transmissions. There are universal bell housings to connect most popular truck engines and trannys. While I like a twin stick in theory and they are fun for a while they get tiring if you need to do much shifting. It was one of those skills I'm glad I learned but doubt it would make for a fun vacation and would be unnecessary in such a light vehicle.
You would probably buy a good Allison that will live forever for what you'd spend on multiple E4ODs.
You need a tach and some math before you think too hard. What RPM are you running at 60? If you're in the meat of the torque curve (2500?) then a different transmission won't to anything for you. If you're spinning out, above 3500 probably, then you need to figure out what gear spread you need to get the speed/RPM you want. You really need to find a transmission that will get you there without having to muck with the rear end.
rslifkin wrote: I just did a little math. Assuming the tires on the bus are 11R22.5 and top gear in the trans is 1:1, you should only be turning ~2600 rpm at 60 mph with the rear end in high (5.38). That makes me think that provided you're staying with gas power, there's no need to re-gear or swap transmissions at this point.
I had a typo in the first post. There were two high rear axle ratios available with the chassis. One was a 5.83, the other was a 6.33
The 5.83 would give me a 2944 rpm at 60 mph. The 6.33 would give me 3196. I haven't actually put a tach on it yet. I'm being optimistic it's the 5.83s.
I know there are guys towing giant fifth wheels with powerstrokes making 800-1000 ftlbs with E40Ds, but they have spent a couple grand on a build. They were factory rated for trucks with 400ftlbs and near 20k GCVW. You can get a Craigslist one for $300 or so. The numbers might or might not work out for you depending on what you are planning.
In reply to mazdeuce:
This is all brain games at the moment. You guys make a great sounding board because you all have different opinions on how to get the job done and you think of things that I miss. When it comes down to it, I don't have to change the gearing or the engine. It's already proved capable of long miles, as long as you don't mind feeding it. I'd like to get the RPMs down though and this is a great place to explore options.
In the long run, dollars spent, a complete diesel swap including, engine, transmission and rear axle is probably going to be the most cost effective way to go. Buy a box truck, use the pieces I need and scrap the rest.
Have you read the code off the transmission yet? You should be able to wheel under there in an office chair. Know the transmission, know the gears, rig up a tach and go do a 'speed' run.
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