International 3800 adventure bus build

HazeltheMooseWagon

Active member


I built the driveline this weekend. I had to remove about 6” from the front shaft and weld on the new 1710 series yoke. This thing is huge!




I measured a 5” drop in 74” from the centerline of the crankshaft pulley to the centerline of the output yoke on the old transmission. Since the bus has 3 sections of driveshaft, I gave the center section the same degree of drop which also matches the rear pinion angle. No vibrations, weird sounds, or heat from any of the u-joints or carrier bearings. I need to change the remaining 3 u-joints as they feel pretty rough. They each took about 8 pumps of grease before they started oozing.

We took it for a short test run and it is so much fun floating through those gears! I found out that it will take off just fine in 3.5 gear (low gear, high range). This means that I will likely drive it like a 5 speed using only high range in normal conditions. I’ll have 6 additional gear choices if I want to go slow. It creeps in low-gear-low-range-deep-reduction.


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baipin

Member
Great move swapping out that awful AT545 for something nicer. Being able to split gears is a lot of fun and real handy in something as big as a bus.
 

HazeltheMooseWagon

Active member
I haven’t posted anything on here in a while. Life has been pretty busy lately but we have been able to use the bus a little bit.

We have installed the glass in the doors and the back wall and tinted a few of the front windows. I also installed a lock on the front door and most of the rubber gaskets around the doors and windows.

We drove an 86 mile loop through the Ouachita mountains and averaged 12 mpg with the new transmission. I’m still learning how to shift it smoothly but I’m getting better each time I drive it. It started raining and the roads were deteriorating rapidly. I had to use plenty of momentum to get up some of the hills. Those bald 11R22.5s don’t grip worth a darn!




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shortbus4x4

Expedition Leader
Yes it does.
I just went a picked up a RTO610 for my shortbus 4x4 build, bought it last year. Have a 1997 DT466 with a p pump to put in front of it. Hopefully this fall I'll start on the repower.
 

HazeltheMooseWagon

Active member
Yes it does.
I just went a picked up a RTO610 for my shortbus 4x4 build, bought it last year. Have a 1997 DT466 with a p pump to put in front of it. Hopefully this fall I'll start on the repower.
That’s going to be a really nice powertrain! I wish that my highest gears were a little closer together like yours. The engine you have is legendary! I’m really enjoying learning how to drive mine. There’s definitely a learning curve with a non-synchronized transmission. The best help I have found so far was a YouTube video where a guy shows you how to recover a missed shift. It has really improved my experience. I’d like to see pictures whenever you get a chance.


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HazeltheMooseWagon

Active member
Does anyone have experience with Fabco front drive axles in a medium duty application? These seem to have gear ratios that are better suited for my build. I can’t find a locker for this exact axle, but I found an Eaton No-Spin for similar axles with the same spline count. It may be worth a try. These have the favorable S-cam brakes and the chunks appear to be reversible for rear steer capability.





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shortbus4x4

Expedition Leader
I think that is a little big for what you're running. Look for some axles and transfercase from a Forest Service 4x4 engine. Mixer axles are for lots and lots of weight so the pumpkin is centered and huge. The smaller axles found in an International 4300 size 4x4 have the pumpkin off center. I have never seen a front axle have a diff lock except for military, but lots of the civilian medium duty 4x4 rear diffs have a air shifted selectable locker. You will be most likely paying lots of money to make your bus 4x4 and parts are not cheap for the front axle or transfercase. Where are you at?
 

baipin

Member
I am familiar with FABCO axles as I was considering them for my build and when I was wondering an even larger bus than what I have now... (but I don't need that massive of a GAWR, nor those ratios, so I went with a Jana 76 front axle).

In any case; like someone else said, the older axles used bushings where you'd expect bearings. I'm not sure if that's a mark on their overall quality or just a product of the company's focus on low-speed all-wheel-drive farm and industrial equipment (e.g. the Fabco WT lettuce trucks). Those axles are typically - from what I've seen - the ones that use International RA-30 pumpkins. So, avoid those and you'd probably be fine. Fabco supposedly went out of business in 2017. Yet I know a local 4x4 MDT conversion shop - Simmard Suspensions - still uses Fabco axles and transfer cases alongside Marmon Herrington stuff. I had asked them if Fabco was still around, and they could not provide a clear answer. Pro Gear and Transmission has plenty of parts but you pay for it. From what I gathered, it's difficult as all hell to find Fabco-specific components, however, I suspect the later model axles would use relatively common bearings and races - brake components might be pricey/difficult to source though.

One option to consider may be a Rockwell axle with Ouverson 4.9:1 gears. 2.5T axles should have a GAWR of 12,000lbs. International 3800's that I've seen, all came with 10,000lb fronts, and International 4300's were spec'd with 8,000 to 14,600lb fronts, if I remember correctly.
 
I've always thought about the concept of 4x4 converting a Medium Duty International Bus. One thing I noticed with 4x4 MDT is that the cabs always sit substantially higher than the 2wd trucks. I've always assumed it was a clearance issue because of the straight axle and large pumpkin. Is that something you'll have to address with this bus?
 

HazeltheMooseWagon

Active member
I think the engines must sit higher in the frame in a 4x4 MDT, thus necessitating a raised cab. My bus engine sits low in the frame with the bottom of the oil pan a good 4” below the bottom of the frame rails. I think that an offset front differential would allow me to package everything in a way that would eliminate the need to lift it 12” to clear the oil pan. I’m not opposed to modifying the oil pan and pickup tube to offset it for the driveshaft without reducing oil capacity. A left-hand offset pumpkin would play well with the right-side exhaust down pipe, but most that I have found are right-side pumpkins. A few front axles have flippable diffs or spindles that would allow a left-side operation.

A 4x4 conversion is definitely on my mind, however not pressing, and not happening anytime soon. I do however want to go ahead and buy/install 395/85R-20 Goodyear MVTs on military beadlocks. The ones I’m looking at come off of the LMTVs and have the 11-1/4” BUDD style bolt patterns. I didn’t realize so many of the mixer truck front drive axles have the 13-1/4” bolt patterns. I know you can get the MRAP wheels that have the bigger bolt pattern but I don’t want to change wheels again in a few years. I’m a fan of doing the job one time and doing it right.


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shortbus4x4

Expedition Leader
To my knowledge the cab and engine mountings are the same between medium duty 2x4 and 4x4 trucks/buses. I've worked on a few of them and own some older International Loadstars in both flavors. I know International and I think Bluebird 4x4 school buses start as a 2x4 and go to Tulsa truck for the 4x4 conversion.
 

baipin

Member
One of FABCO's "big" innovations was the offset pumpkin (well, not their innovation I suppose, but they made great strides in popularizing it with MDT's). It's what allowed them to make trucks like the International Unistar 4WD without raising ride height that much - very important for a cabover of that size.

If you do a 4WD conversion, be careful about your driveline geometry. My bus would be a "class 4" but even at that size - and surely anything larger, like your bus - you're looking at drop cases. A NP205 would of course be too light for my needs. NP200 would be appropriate but parts are rare. A NV271 could have worked but I'd prefer a gear-driven case. I ended up with a 2.5 ton Rockwell T-136-27 airshifted case. They're cheap, simple, and strong as hell. I could see something like that on your bus, or a 5 ton variant, or Axletech's offering; the T600. When you get outside of military surplus cases, I find parts availability to sparse and expensive. But regardless, you're almost certainly going to end up with a drop case.

I was fortunate that, since I am swapping in a DT360, I could play around with driveline geometry all I wanted. If I were not able to raise the engine and transmission mounts up to the top of the frame and lessen their angle by 2 deg. I'd be looking at a pitiful 11" of ground clearance. My frame height sits at about 41" at the top flange to the ground, so nothing unsual. Just be aware of that for your build. The length of a big Eaton trans, and then the jackshaft, and then the transfer case itself, really makes the inches add up with every degree the engine is angled back. Most bus bodies I've seen sit 4" above the actual frame - so you should be able to mount the engine quite high with room to spare.
 
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To my knowledge the cab and engine mountings are the same between medium duty 2x4 and 4x4 trucks/buses. I've worked on a few of them and own some older International Loadstars in both flavors. I know International and I think Bluebird 4x4 school buses start as a 2x4 and go to Tulsa truck for the 4x4 conversion.
Every International I've seen (4700, 4800, 4900, 7300, 7400, 7500, etc.) I've seen has a cab thats substantially higher than pretty much any 2wd alternative. I've also noticed this on Freightliners, and Fords, (F650, F750, and older F800s). They all have a ton of wheel gap and sit very high.
 

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