L J Mack Transmission ( Coca Cola)

[1961H67]

Just thought I would post this picture and find out if anyone has ever driven a truck with this model transmission, I drove this truck when I was about 19 years old, I rode with the fellow that owned it ( that I later inherited from) and drove it myself for a while, the transmission made a lot of noise and he said it was getting worse, so we pulled it out to replace the bearings, I didn’t recall it being a big ratio jump when you split the auxiliary, but it was the original and was a overdrive. In the meantime we had a junked F Model with a direct 10 speed, we put in it ,  shifted good, split well, so we just left it in ( slowed it down to about 60:but we were not using it much) When I restored it I had a 1950 LJ with a gas engine, it was a factory order dump truck, I checked the transmission and it was a overdrive so I installed it, the shift pattern was like the original  3rd & 4th beside each other, I used the shift pattern plate from the 50 gas , My question is was this a special model for a dump ? When you try to split the auxiliary it’s like jumping 3 gears, It is an overdrive and works well driving to shows , any thoughts? 

[mechohaulic]

vaguely remember a transmission having the odd ball main pattern; more than likely a truck that came through the ranks while I worked at Mack. plate shows as underdrive ; possibly where Mack engineers thought up the later 6 speed used in off highway units.

[1961H67]

Yes it has that odd ball pattern. 1st is completely on the opposite side then 2nd , and the original one was the same, but the original could be split between main gears like the 10 speed, this one has a WIDE auxiliary ratio , and is super slow in 1st under drive, the only way I can drive it is leaving the auxiliary in direct and shift like a straight 5 speed.  I’ve got 5 trucks with Dupex,s and this one is the only one  that’s geared that way. 

[steve s.]

I have some old Brockway gas jobs with Fuller overdrive transmissions that use that same 5 speed pattern. It's a long way from 1st to 2nd. As for your other lever, I recall hearing old-timers refer to it as the "mud stick". It is a real lo hole that is really only meant for something like  on/off road dump truck use. It was ok with a gas engine, and it might work well with your Cummins, but that transmission was never meant to be used with a Mack Thermodyne diesel. It just doesn't have the gear splits you'd need to stay in the narrow power band. 

[Brocky]

A man I worked for while in high school had a 1958 or 9 Brockway with a 220 Cummins and an Overdrive Transmission that shifted like that , but I do not remember where 1st and reverse were. It was a single axle with an air shift 2 speed rear and you were not supposed to use the rear in low when the main was in overdrive.

[1961H67]

Steve that sounds like exactly what I have, I’m not going to change it because it’s still a overdrive, and the lowest gear is handy loading on a trailer when hauling it, I have another LJ parts truck that was a Diesel but was in the flood and the original was probably hauled off for scrap years ago, The number on it was the same as the line set record  the Mack Museum sent me , 720 I think, but the rear auxiliary must be were the difference is . I have a photo of the LJ gas when it was in use here in North Carolina, I knew the original owner’s Grandson , he gave it to me for parts . Now we know what the Low Gear was for. 

[mattb73lt]

When I was building my B42 and converting it to diesel I parted out a B61SX dump truck. I bought it mainly for the transmission. I didn't know a lot about B models back then. The transmission ended up being a TRDX-72. Which was a direct gear Duplex with a deep reduction in low range. You didn't split it. Five in low range, then five in high range. What some call a "dead stick" duplex. It did have a normal H pattern five speed for the main. Your transmission sounds like it works similarly, just with that odd gear pattern. That transmission was the only thing I didn't use from that part out.

[1961H67]

That’s probably close to what I have, I’ll recheck that trans number, just for curiosity. 

[The Heinz]

Is there a name on that locomotive? I can't tell on my work PC screen. Would love to know the history of that unit and what may have happened. 

[mrsmackpaul]

18 hours ago, steve s. said:

I have some old Brockway gas jobs with Fuller overdrive transmissions that use that same 5 speed pattern. It's a long way from 1st to 2nd. As for your other lever, I recall hearing old-timers refer to it as the "mud stick". It is a real lo hole that is really only meant for something like  on/off road dump truck use. It was ok with a gas engine, and it might work well with your Cummins, but that transmission was never meant to be used with a Mack Thermodyne diesel. It just doesn't have the gear splits you'd need to stay in the narrow power band. 

I believe your right in this been a Fuller transmission 

We were discussing this very thing on a Australian truck forum just the other day 

A bit like the road ranger when you swap the cogs about to give you overdrive 

Anyway, enough from me 

 

Paul 

[mowerman]

man thats a really wierd shift pattern,,,i have never seen...but tall gears are always a pleasure   bob

[1961H67]

Heinz , I ran across that picture looking at some old Hennis Freight Lines photos. If you look closely in the lower RH corner you can see it says DigitalForsyth , Where Hennis was from in Winston Salem. Crouch Brothers was a Construction Co and House Movers, they had a location in Asheville and Charlotte ( That LJ was used in Charlotte and sent up here , they were going to restore it because there Grandfather bought it new, but never did anything with it so the Grandson gave it to me, they said he ordered it for a dump truck but put a 5th wheel on it to move houses, it’s double framed with the biggest stack of springs I ever saw on a 1950 truck) , Anyway that Locomotive must have been moved down towards Winston Salem, Probably in the 60s , I can’t read the name, you might look at some Winston Salem historical pictures and find something. 

[yarnall]

That is the same shift pattern and plate that is in my 1950 LFT from Ralph Smith.  Mine has a Lanova.  I don't know the proper way to shift it.  I often run it up in low then shift to high in 4th or 5th.  I will split is sometimes and that works.  My 1947 85LS firetruck has the same shift pattern with a straight 5 speed.  I have to think when I shift them or I end up in the wrong gear.  My 72 Transtar has that reverse shift pattern mentioned above in a 13 speed roadrunner to make it double overdrive.  That is way faster than the other trucks.    Mike

[Geoff Weeks]

I drove a IHC firetruck that had that shift pattern, also my parts Fleetstar did also. odd, but not on common. 1stwas really low and not used when on hard pavement.