Mack B Model Custom/Repower/Chassis Swap

[r8f1k]

Ok, so I don't have anything written in stone.....but I am looking to build a semi-custom vintage Mack.  B model seems to be the best overall size for me.  I would like to either engine swap a Model B with a Ford 7.3 and auto trans or a DT466 with an auto trans.  I really only need something with a single rear axle and a flat bed.  I would like a truck with A/C and power steering.  I have lots of fabrication experience and I have plenty of mechanical experience.  This would be a project for my auto shop, I am a high school shop teacher and my students are always looking to do a swap and build something cool.  This would seem to fit that bill.

My questions are:

Is it better to find a Mack cab and swap it onto a modern chassis?

Is there enough room in a B Model for either engine?

Has anyone done a swap like this?

What should I look for/look out for/avoid?

I also found a 1964 Mack B61, any idea what transmission would make it more highway friendly? 

Can someone remove an axle to make a single axle unit?

Any thoughts are appreciated!!!!!

[66dc75]

You want to do a pick up or a medium duty? This is on a 3/4 ton Chevy chassis

[mechohaulic]

what ever the out come; sure hope the BMT crew is kept updated. which way  is chosen by you/class would depend on available Resorces. take a dual wheel  pickup  swap Mack cab on to it might be easier for school tech group. to take a mack chassis and swap over could be challenging for class to operate on highway. much depends on the class abilities which is a question YOU could answer better then anyone. 

[mechohaulic]

Mack did make a B-20  ; smaller cab . also it doesn't have to follow a pattern  being a B-model Mack. the A series or E series Mack aren't usually used, think out side the box and build different. E series dual wheel pick up having updated running gear (AC/ power steering ) with twin stacks. 

[Brocky]

This Is a Brockway sheet metal swap onto an International Harvester U haul Chassis and power train.. He was pulling a 5th wheel camper with it. I thought he did an excellent job and was very proportional size wise..

And here is another that I did NOT like!!!

[mechohaulic]

many yrs back my '77 F-350 dual wheel truck was showing signs of age and rust. a local road sealing co had small short nose Brockway used for back up emergency.  flipped the idea of a cab swap. would have made sharp looking dual wheel flat bed Brockway. like rest of my life everyone else iron took preference. time went by /sold the F-350.

[r8f1k]

So, I would love to engine swap a Mack, just to keep it as 'truck-like' as possible.  My students are pretty good.  I think a big project is something do-able for the crew I have and will have.  

I don't really like the pick-up truck look with a cab on it.  Just a little too small for me.  I do need a truck that can haul a skid steer, tractor, vehicles, farm stuff, etc.  maybe a capacity of 15,000-20,000lbs hauling ability. 

I also found this Diamond REO truck that would almost just right, but I think it is a little too big.....hence the interest (from what I THINK) is a little smaller cab in the Mack B.  The Diamond would, in my mind, be ripe for a 7.3 swap.....the issue is the two speed rear end.  How would that work out?  I don't mind a bouncy ride, but I don't want something that shakes your fillings out of your teeth.  Would one be able to add air ride to a cab of these ages?

[Brocky]

That Diamond REO has some good possibilities!!! Do some cab interior measurements, that REO cab may be bigger than a Mack?? Then measure the operators, I am 6'4" / 250 lb and do not fit well in a lot of the older cabs!!That is the REO cab, BUT BUT NOT D/R fenders!! They look homemade?? Diamond T, Diamond Reo, REO and White 2000's all used the same fenders so you should be able to find a correct set. Is it a gas job or diesel??? If it is a gas job and you swap in a diesel, you will probably have to change the rear?? First you must make your choice of engine, the 5.9 and 6.7 Cummins are very good engines, Then determine the engine's operating RPM's and the cruising speed you want, then do the math to come up with a workable rear end ratio.. You may be able to kill 2 birds with one stone by swapping in an air ride single drive axle????

Please keep us posted on you thoughts and progress.

[r8f1k]

28 minutes ago, Brocky said:

That Diamond REO has some good possibilities!!! Do some cab interior measurements, that REO cab may be bigger than a Mack?? Then measure the operators, I am 6'4" / 250 lb and do not fit well in a lot of the older cabs!!That is the REO cab, BUT BUT NOT D/R fenders!! They look homemade?? Diamond T, Diamond Reo, REO and White 2000's all used the same fenders so you should be able to find a correct set. Is it a gas job or diesel??? If it is a gas job and you swap in a diesel, you will probably have to change the rear?? First you must make your choice of engine, the 5.9 and 6.7 Cummins are very good engines, Then determine the engine's operating RPM's and the cruising speed you want, then do the math to come up with a workable rear end ratio.. You may be able to kill 2 birds with one stone by swapping in an air ride single drive axle????

Please keep us posted on you thoughts and progress.

I'm 6'0" / 200lbs, I'm no giant, but my concern is just having a giant truck.  I had a 1993 Kodiak, that was too much.  Anyone know how this Diamond compares?  

The Diamond is a gas unit, 2 speed rear end.  I love the idea of the Cummins, but they are always soooooo expensive!!!!!  Is it possible that the existing transmission could be used with a Cummins?  Anyone know what the highway speed of a truck like this is?  

Also, is it kosher to talk about other brands on this forum?  If I were to proceed with the Diamond, would I have to switch to a different thread?

Here are some more shots.

[mattb73lt]

Drive line swaps are usually the easiest way to make an older truck more "roadworthy". A lot of more modern components will bolt right up to an original frame. Switching to a single axle arrangement can be done, but you're not going to split a tandem/bogie arrangement into a single axle. You'll need four spring perches and parallel leaf springs and a different axle. A complete frame swap can be another way to go, like putting an entire 1 1/2 ton GMC dually frame under it. Another benefit of a modern drivetrain is if you are far from home and you happen to breakdown fixing it is a lot easier than something that's vintage. Bringing modern amenities (A/C ,Power steering/brakes, cruise control) can be a lot easier to do.

Sheetmetal can be another issue. The cabs usually aren't too bad, as they were all pretty small back then. The front end is usually the hard part. Re-scaling the sheetmetal to look right is a task. Resizing fenders to fit smaller diameter wheels, shortening hoods, shrinking radiator shrouds. As you can see from some of the pictures offered above, some get it right and some don't. It's really up to you and your resources as to what you can do. Talk to people, go to truck shows, internet searches can all help you develop a plan to move forward with to built what you want.

[yarnall]

5 hours ago, mechohaulic said:

Mack did make a B-20  ; smaller cab . also it doesn't have to follow a pattern  being a B-model Mack. the A series or E series Mack aren't usually used, think out side the box and build different. E series dual wheel pick up having updated running gear (AC/ power steering ) with twin stacks. 

The B20 cab is not smaller. It has a smaller engine and lighter suspension. 
Mike. 

[JoeH]

As someone who owns one, I don't think you can beat a 5.9 12v Cummins, but I understand they may be pricey.  They use a hydraulic brake booster off the power steering pump, so you remove the need for a vacuum pump.

Personally I'd stick to a mechanical engine. Fuel and coolant and oil and you're running. 

Not sure what region of the US (I assume) you're in, but in PA there used to be a lot of Ford L8000 single axle oil delivery trucks. I have one I converted to a dump truck that has an 8.3L Cummins with a 6 speed transmission. Rear axle is geared for local driving, it'll do 55, barely.

Edited December 19, 2023 by JoeH

[JoeH]

Also not sure what your state's driver license laws are. In PA, a CDL is required for anything over a 26,000 lb weight rating. Also need an air brake endorsement to drive trucks with air operated brakes. And now if you take your CDL skills test in an automatic, you're restricted from driving manual transmission trucks.

If you're looking to have a payload of 15,000-20,000 lbs on the truck then you're looking at needing a 33,000 lb GVWR, which in PA is max on a single axle truck. If you're trailering the load then that may buy you some wiggle room on the truck chassis you swap a cab onto.  I believe you still need a CDL in PA if the gross combined (trailer and tow vehicle) weight rating exceeds 26,001 lbs, but I've always been fuzzy on the details on GCWR.

[JoeH]

8 hours ago, r8f1k said:

Can someone remove an axle to make a single axle unit?

Depends on suspension. Mack Camelback suspension, no, not without swapping entirely different suspension and axle in, which is entirely doable.

[JoeH]

4 hours ago, r8f1k said:

Would one be able to add air ride to a cab of these ages?

Air ride cab no, don't think so. Air ride rear axle, yes.  Air ride cabs, the front cab mounts would need to be hinge type pivots while the rear cab mount is air bags with a leveling valve.  The issue will be on hood impingement. The cab will need to rotate on the front cab mounts, which will crush into the butterfly hood.

[67RModel]

I would repower/regear an original truck. My personal opinion is medium/heavy duty bodies swapped onto a pickup chassis look like clown cars to me. I have a friend who put a B model cab and front clip on an international S series chassis and it turned out very nice.  I would look for an International/Navistar mechanical DT360 engine. They are the same size (360 cu in) and dimensions a 5.9 Cummins and just as bulletproof. Plus nobody has one. A 5.9 swap is so tiresome. I like the 2 speed rear end especially if you are going to be hauling weight. The one in that Diamond Reo is probably geared super deep though. I would look for an old International S series parts truck or 90s Ford F700 with 2 speed rear for the axle and transmission. Whether or not you decide to go air brake or hydraulic brake will dictate a lot about what axles/ratios are available to you. Either the DT360 or 5.9 Cummins can be outfitted with an air compressor so it would be possible to do either hydraulic or air brake.  Good luck.

[Brocky]

You have a LOT of research to do before you make any decisions.. I do not know how much a skid steer weighs but it would take a pretty good sized old farm tractor to get above 10,000 lbs.. The Brockway in my top picture was a U-Haul IH chassis (one of their big vans) and power train on 17.5 tires, which is a good size, and long enough, for what I think you are thinking of building?? I took that picture in 2012 at Cortland NY so God only knows where it is now to find and contact the owner!!! Contact the Public Relations office of your state's "Diesel Cops" as to what licence category you will need?? Most states if you are only going to use it to take stuff to shows and DO NOT DO  any revenue generating work you may not need a CDL??

[Freightrain]

Skid steers are around 7k lbs depending on version.  Moving my friends on his big tag trailer it pulled heavy, similar to my race trailer(14k lbs).

 

To get around some of the legal logistics, maybe a juice brake S series International chassis with a B cab put on?  That could get you under CDL issues and still pull okay.  Ex Uhaul chassis might be a cheap buy? 

Might want to get a mechanical Dt466 or 12v Cummins to get away from electronics on the engine.  I know someone with a S series pulling a race trailer.  It's governed to like 52 mph.  Dealership can't do anything for him.  It was a local Chemlawn truck, so never meant to go fast.

 

Most any B will be gear bound without changing the rear axle.  Most built to go 45-55 mph.  Mine originally would go 65 mph flat out, but many don't.

 

Most 2 spd rears aren't really fast either from my experience.  Marginal at best.  Finicky also with inexperienced operator.

[tjc transport]

Larry, my cat skids are in the 12,000 to 13,000 pound ange.

[r8f1k]

So a couple notes:  

1) I qualify in Wisconsin for AG plates and license on a truck up to about 30,000lbs that is used for AG purposes and only driven something like 5,000-7,500 miles a year.  That's with or without air brakes, no CDL needed.

2) I would like to go around 65mph since I do move equipment between farms that are quite far away from one another.

3) My skid steer is about 6500lbs, my trencher is 8,700lbs and my heavy tractor is 9,000lbs.

The seller added some photos and added this info on the Diamond REO:

Engine Model: 6-170

Transmission: 282V

Rear Axle: 16220   H-1760

Front Axle: 32550   HX67

Steering Gear: HPS70

 

[r8f1k]

3 minutes ago, tjc transport said:

Larry, my cat skids are in the 12,000 to 13,000 pound ange.

I do plan on upgrading skid steers in the not too distant future, so I bet it will be much heavier.

[Brocky]

When you get up into that weight range Air brakes are much safer and more reliable.. AND easier to service!!!

[mechohaulic]

16 hours ago, yarnall said:

The B20 cab is not smaller. It has a smaller engine and lighter suspension. 
Mike. 

apologize for incorrect info ;; B-20 lighter drive train ; smaller wheels size (in some instances) possibly work better  for  this application. 

[JoeH]

Sign up for an Edison Motors diesel electric power swap! If you're training up the next gen of auto techs this is where the future is!

[r8f1k]

There seem to be more B61's around than B20/21's.  Would the recommendation of swapping a DT360 or DT466 with a more modern transmission be an option?  Any idea of what transmissions to look for or avoid?  Best rear end to look for?