B model gear ratio

[nasty51ford]

Hi, I recently purchased a 1958 B67T, it is a very solid truck, has a sleeper, and an 18-20' tilt bed on it, it was used to haul a race car, the problem is, it is only geared for 55 MPH !! It has a duplex, and fifth gear has been turned around, to make it an overdrive (at least that what the guy told me, and so far every thing else he has told me has been true. I just haven't been able to take it down the road yet! I am trying to find out what kind of ratios are available for this truck, or if the newer single axle differentials will interchange, or am I going to have to put a whole rear end out of a later model truck? I will go insane if I have to make a long haul to get a car or two and can't go over 55 MPH !! Lol !! Help !! I would trade it also, for another old Mack,Brockway, or Autocar, that is already geared for the highway, and maybe has a flatbed, or is long enough for one, if not, a short one will work, because I have a 20' car trailer.

Thanks

Keith

[j hancock]

Depending on your long term plans for the truck, swapping in an air ride suspension and better ratio may be the way to go.

Also keep in mind, you can't get too carried away with your ratio depending on what your HP is. You can only pull so much gear with 180-195 HP on tap.

[mattb73lt]

I removed the original carrier from my RAS-508 rear axle, it was around a 5.70 ratio and single reduction. Replaced it with a CRD-117 double reduction carrier from a R Model, with a 4.62 ratio. It was a direct swap with no modifications. This all was in a B-42 that I swapped the drive line out of. I do have a double overdrive Triplex in it behind a 237. If you can figure out what overdrive your transmission has it will help you with finding the right ratio for your application. The R model carriers have a wider range of ratios and will be easier to find. Did mine about 15 years ago and have never had any issues with it. I can dig up the exact details if you need it, but the above info was off the top of my head.

[theakerstwo]

I have a air ride mack complete with 4.63 ratio for 1,000 dollars if you need.

[Freightrain]

That duplex is likely a 9spd, I think that is the version that has OD in 5th? The 10spd is direct in 5th. Mack built them either way. Check the side of the pumkin, it should have a number stamped in the side that denotes what it is. Probably 5.xx something. When I had 4.63 and single OD, mine would run 63-65 mph.

Currently I have 4.10 and enough overdrive gearing to run 85 mph. It runs along at 68 at 1800 rpm and does well with my trailer. I too was concerned with over gearing and not having enough power to pull it. All depends on your terrain. Flat land is good, hills will really slow you down.

[nasty51ford]

Hi, I live in Florida, so all flat land, all I will haul with the truck is one car 90% of the time, the rest of the time I will be empty, and once in a great while I may have two cars on it, the shift pattern diagram plaque in the truck shows the ten speed direct shift pattern, but the guy I got it from told me that top gear has been turned around, so that 5th gear is up against the dash. So I don't know if that would make it the same as the 9 speed OD or not, I'll have to go get the numbers off the trans and rear, I was just curious what gears are available, and whet the interchangeability scenarios is? But I guess if later model "R" model diffs are the same (bolt in) that will help a lot, it is a front loading diff buy the way

Thanks

Keith

[Freightrain]

I know that they flip gears around in a Roadranger, but didn't know they could do it in a Mack transmission?

[nasty51ford]

Yeah, me neither, that's what the guy told me, maybe it just actually had the trans swapped, I'll have to het the numbers off it

Edited August 15, 2014 by nasty51ford

[Bigdogtrucker]

I'd just enjoy the ride at 55 for now til you get the parts for a gear swap .Did the guy tell you it does 55,or have you driven it?

[nasty51ford]

No, I haven't driven it yet, he drove the truck down from Gainesville area, about a two hour drive, and said it did 55

[Bigdogtrucker]

My advice BEFORE you do anything.Get a GPS with a speedo on it,or get an app for your phone that does the same and check the speed to be sure.Had a buddy that was gonna swap gears on an old truck that did 55 according to the factory speedo,turns out it was going nearly 65!

[nasty51ford]

Yeah, I was thinking the same thing

[Bigdogtrucker]

Speedo may be right on,but ya never know.All kinds of things can be done to these old trucks over the years.

[Freightrain]

Just so you know, 4.00 to 9.50 were the ratios available, at least from the information I've looked at.

I remember Highpoint Garage having a B model for sale with 9.50 gears in it. Yowza!!!!

[Red Horse]

My advice BEFORE you do anything.Get a GPS with a speedo on it,or get an app for your phone that does the same and check the speed to be sure.Had a buddy that was gonna swap gears on an old truck that did 55 according to the factory speedo,turns out it was going nearly 65!

Bigdog- I have "Maps", MapQuest, and WAZE on my IPhone (4) do any nof those apps give you the speed check feature???

[HarryS]

I went from a TRD 72 10 speed direct to a TRD 720 9 speed OD. Not sure what axle ratio the 720 came out of but the speedo was slow by about 8 MPH (verified by GPS) with my rear ratio of 4.28. I swapped the speedo gears out of the 72 and that corrected the speedo. The TRD 720 has that screwy shift pattern with 3rd and 4th at the seat and 5th at the dash. I noticed in the service manual they talk about an extra "pivot pin" in the OD transmission to make the shift pattern the same as the 10 spd direct. Maybe the shift mechanism has been changed somewhere along the line in our OD transmissions. Very cool truck by the way. I'll be anxious to hear how it drives.

[Bigdogtrucker]

Red Horse not sure,i have the Android Speedometer app.I'm sure there's a lot of different ones.Sure is nice to have!

[Red Horse]

Red Horse not sure,i have the Android Speedometer app.I'm sure there's a lot of different ones.Sure is nice to have!

10-4-as always I'll have to ask my kids

[Maddog13407]

I had a whole paragraph typed up on this but my computer seems to be ''a different kind of retarded' today for some reason. like the guys said put a gps in ad drive her first. if you have a single reduction housing, you CANNOT put a double reduction hogs head in it. it will bolt up but the housing doesn't have the webbing to support the bearings and the ones I have don't have the cones under the axle nuts. looks like you are running 20 inch rubber. that loses you a few mph's right there. and like the other said, with a natural 673 you wont have the grunt to put too high of a gear ratio in her. my B613T had a turbo engine with a triplex , on 22'' rubber with a 4.66 ratio from the factory. im runnin a end707 with a triplex and a 4.00 ratio on 22'' rubber now. I don't think I could run this combo if I had a 673 natural.

[nasty51ford]

Thanks everyone, and Freightrain, the guy with the 9.50 gears must have NEVER left the jobsite! Lol. Yeah, I have been wanting an old A-Car, KW, PETE, Brockway, or B Model Mack forever, (an LT is just a dream! lol) just because I remember riding in them when I was a kid with my dad and uncles, I had a 71 361 Brock back in 84-85, it had a 1974T cat that was turned up and had enough torque to move a mountain, it had 4.11's and a 13 double over, I loved that truck, it was black with chrome Farr air cleaner, bumper, grille, and chrome straight 6" stacks, wish I had it now, back then I didn't think it was all that old though! lol

[mattb73lt]

Maddog 13407, I was told I would need a double reduction axle (RAD series) for that chuck or need to modify the original. I bought it with the axles and they did have the cones. Pulled the axles and carrier from the housing and compared everything closely for fit. The original axles had the cones, so I reused them as they were in better shape. As for the carriers, all the mounting areas were identical. there are four pads on both carriers in the back that are drawn into a ring internal to the axle housing for support.. The major difference was the external areas to house the extra set of gears, making the double reduction housing longer and requiring driveshaft shortening. My original engine was a END-673 and was upgraded a few years ago to a 237. The whole truck has been together for 15 years and I have never had any rear end issues with numerous cross country trips with various weights on it. It is possible to do that swap. If his truck was always diesel it will probably have the double reduction housing to start with.

Edited August 16, 2014 by mattb73lt

[Maddog13407]

yup,not many had the single reuction rear. I know the few I have had were gasjobs and they didn't have the cones under the axle nuts and didn't have the extra webbing inside to support the beaings/hogs heads. I have repowered many gas job B42 single axles . some I just changed the hogs head, some I had to change the whole housing.

[nasty51ford]

Maddog, do you think the non turbo 673 will pull a higher gear empty, or with just one car behind, or on it? I just want to be able to cruise 74-75 MPH.

Thanks

[doubleclutchinweasel]

Maddog, do you think the non turbo 673 will pull a higher gear empty, or with just one car behind, or on it? I just want to be able to cruise 74-75 MPH.

Thanks

My truck has 4.17 gears, and a direct-in-high trans (1:1). It will cruise at 55-60. 62-63 is about all she wrote. But, 60 isn't too bad. So, let's call this one a 60 mph truck.

Depending on the overdrive ratios, of course, a single overdrive (lets call it 0.84:1) will get that 60 up to about 70. A double overdrive (like 0.70:1) will reach about 85...in theory!

[Freightrain]

I tjhink it will struggle to keep up 75 mph with one car on. My GCVW is around 27K lbs and 65-70 is comfortable to run with 4.10 gears. Just runs outta power trying to keep up any faster speeds and it will not pull hills well. I can use my last OD and pass someone and run it up to 75 or so on level ground, but it just doesn't have the power to keep it there.