mattb73lt

I did the same swap on a '63 B42P. What saved me a lot of pain and aggravation was buying the front half of a donor truck, a'65 B61SX. The Mack frames are pre-drilled to accept gas and diesels. You'll need to swap the front cross member and the transmission mounts. As for an engine, I used a END-673. A 237 should bolt right in with some bolt on mods,possibly the bellhousing to position the starter and avoid interference. I also put in a TRTL-720 Triplex. I kept the original rear axle but swapped out the carrier from single reduction to double reduction with a 4.62 final drive. Over all, a very easy swap if you use Mack components. The donor truck was invaluable for all the small bits you'll need, radiator shutters, brackets plumbing. That cut down significantly on parts hunting and fabrication. You can use any engine you really want, if you have the time, patience and resources to expend. I would recommend swapping the transmission as well, the small one won't stand up to long with a bigger diesel. I ended up with a really fun truck that has enough power for what I need, hauling antique cars on a roll back body I added and speed, I can do 65 MPH all day turning about 1700 RPM's. Top end is about 80+ MPH, but don't forget you have to stop all that weight. Good luck, Matt

I have a TRD-67 tenspeed direct duplex out of my B42P sitting on my floor. No known mechanical issues with it. The previous owner welded a broken portion of the bellhousing back on, but it never gave me any problems. It's located in Berlin, CT. Let me know if your interested. Matt

Paul, Yes, I'm running a double overdrive. My set-up is a END-673(N/A) backed by a TRTL-720 through a final drive of 4.62 with 20" rubber about 43" in diameter. The Triplex has fifteen speeds but you only use thirteen as you don't split Fifth. It's a pleasure to shift as you can skip some of the splits depending on loading. Most of the ratios have about a 300 RPM drop and it shifts very easily without the clutch. The upper gears are great for hill climbing and I can't recall having to go below 4th Lo-split on the highways around CT with the loads I carry(antique cars and pickups). When I was collecting up the parts to do the project I bought a book about auto math to get the math equations for gear ratios, very helpful!! Then I started to play with them to determine the final drive ratio, then found one to with the right ratio complete the set-up. I ran the equation for each ratio to confirm the shift points to make sure I was in the power range of the engine. It seems as if everyone here has been very helpful and in the same ballpark with answers for you so you shouldn't be off when you set yours up. By the way, if anyone needs a TRDX-720 Duplex with a deep reduction and a single overdrive(.86) out of a B-61SX or a TRD-67 Baby Duplex, direct, I have one of each. Let me know if you need any thing else. Matt Let me

I Have converted my B42 to a "B43" by adding a END-673 and a tri-plex. The give-away on the tri-plex is on the stamped info on the Left side. There's a TRTL and a TRT. The first one is a Light or aluminum case, the second is the heavier cast iron case. Then theres the numbers, 72 means you have a single overdrive, 720 is double overdrive. First overdrive is in the auxillary box, the second overdrive is in the main box. Single over, I believe, is 1to0.86. Doubleover is 1to0.68. It's been a couple of years since I ran all the numbers, so someone correct me if I slipped up! As for coversion by changing the internal gears, due to the scarcity of parts and expense it may be more practical to find one with the gears or to change the rear ratio. When I did my conversion I needed to also change the rear gear set as it was a single reduction with a 6.00 or so ratio. I was able to find a 4.62 CRD-117 chuck from a salvage yard for $500. Due your math on all components to include tire height to due it right. I chose that ratio for the rear for what I due with the truck. Top end for me is about 80MPH with 20" rubber and empty with the engine around 2000RPM. Now, that's way too fast for normal cruise, ie:tickets and being able to stop!!. But, I chose all the parts to allow me to run at about 65MPH and the engine only turns about 1600 to 1700 which is great for economy. I like this set up so well I'm building up my next project, A 1960 B-73LT(L-cab) with the same transmission, Cummins NH-220and a CRD-78 with a 4.68 ratio