John Costley

The trans thats in it started as an RT-11509, then Peter put an RTO-12513 back half on it to get a .87 OD. First gear is 12.50, reverse is 13.07. The FRO I'm looking at has a lower first and reverse, 12.69 and 13.75, and a higher OD of .74. Its a wide ratio ten built for electronic high torque engines, the drop between gears is big enough that they dont work great with most older mechanical engine, but it should be ok behind the Maxi. Biggest reason I'm looking at it is that it should bolt straight up to the bell, though I'll need to have the shaft redone because its shorter than the 13. The kicker is that its only $300.00 and the budget is tight.

Good to know, that will make life a lot easier. Usually when I misremember something it bites me in the ass, good to know its in my favor for once, lol. Thanks

I've never pulled one apart so I dont know first hand, but I remember conversations on different forums where it was said that the Mack sixes, E6 and older, used a 1.75 shaft instead of the normal 2.00 shaft, so to install a Roadranger would require the Mack/Eaton bell with the side mounts and a change from a 2.00 shaft to a 1.75 shaft. I took a look on the Roadranger website today, there is a 1.75 shaft kit available for the FRO series so I'm covered if I buy the FRO-15210C and end up needing it. The FRO has a lower first than the 13 and a higher OD (.74 instead of .87) so it ought to make that little 237 happy on the interstate with the 4.10 rear.

Thanks

Just curious, before I call any parts houses, to see if anyone knows if the E7s used the small input shaft like the E6s did or if they used the bigger shaft like Cat and Cummins ?. I know the FRO10s were avaliable behind the E7s because I drove a '97 CH with an E7 400 and an FRO-14210C. I've got a line on a cheap FRO-15210C, with the wide ratio spread I'm thinking it will work better behind the 237 Maxi thats in Peter J's H model instead of the RTO13 speed thats in there now. The 13 has some issues, I'd just as soon find a good used 5 or 6 speed to put behind it but its already rigged for a road ranger so it will be cheaper to stay that route. If I cant put a small input shaft on the FRO then I'll probably look around for an older RTO15 or just patch up the 13 speed. Thanks

If your dead set on changing transmissions then I'd look around the bone yards and older rebuilders for an RTOO12513. The brochure page I attached shows the ratios for the RT9513, the RTO9513, and the RTOO9513. the 125 series has the same ratios, they just have a higher torque rating. The OD ratio is only .02 lower than what you have, top speed would barely change.

Here are the basic 12V71 truck model dimensions

This advert is a head scratcher for me...I dont believe I've ever seen that grill in any other Mack....no idea what year the advert is...

The Western G...with a New Jersey address....

The '75 Cruiseliner advert and the announcement in Bulldog with the cover

The whole '78 brochure that Sodly posted the cover to, for anyone who hasnt seen it

Nice thread...a slightly different view of the Tip Turbine set up...

Larry, Doesnt look like it pulls much air to spin it over. Have you checked the pressure drop during cranking since you put the new gauge in ?

Gordon drove this B model at that time, Juiced up 400 big cam with a 13 and 3:70s, she would run and Gordon went most everywhere flat footed...

Thats Gordon Chase's old H model that he built for his wife to drive back in the '80s. He stretched the cab and put it on an mid '70s Astro chassis. Cummins powered with a 13 speed, it had a second, smaller radiator with an electric fan behind the cab. She embarrassed a lot of "big trucks" with that little H model. I always wondered what happened to it, nice to see its still alive.