![]() ![]() It was based on the 9 speed direct transmission with a 17% underdrive splitter gear in the auxilliary drive section. The "low" position put the transmission in double reduction and the "Int and Dir/Over)" switched between the low/high ranges.Įaton used to offer a 13 speed transmission with a direct drive 13th gear instead of the traditional overdrive for customers who wanted the flexibility of a 13 speed transmission but the fuel savings of direct drive. On the 3 position 6613 shift button, the 3 positions were "Low, Int, and Dir (or Over)". Switching the splitter from "Low" to "Direct" or "Overdrive" would change the range from low to high. The "low" splitter position took place of the high/low range button. Unlike the traditional 13 speed transmission, the RTO-6613 had the top two gear positions reversed.Įaton used to offer a 3 position splitter button for both it's traditional 13 speed transmission and the 6613. The 6613 was discontinued sometime in the early 80's, though used units are often sought after by medium duty truck owners. It's interesting that Eaton called it a "13 speed" despite it offering 15 separate ratios when on it's 15 speed transmission, which as I metioned before is constructed similarly to the 6613, only 12 successive ratios are available (due to the same overlapping of ratios). While it offered 15 ratios, there were overlapping ratios so there were only 13 successive ratios available, they were typically selected one of two ways:ĭR1-DR2-DR3(shift to low)1-2-3-4-5 (range shift) 6-7-8-9-10ĭR1-DR2-DR3-DR4-DR5(shift to low)3-4-5(range shift) 6-7-8-9-10 Now this might sound familiar since it's similar to how a typical 15 speed transmission is constructed. Unlike the usual 13 speed transmission that was based on a 9 speed main box with a splitter gear, the 6613 used a 10 speed main box with a high/low/double reduction low auxilliary box. The 6613 transmission differed from the traditional 13 speed transmission. The RT/RTO-6613: the 13 speed with 15 gears. It's important to note that the traditional 13 speed transmissions from Eaton starting with RTO do not have the reversed top gear positions since they are actually based on eaton's direct 9 speed transmission with an added 17% overdrive splitter gear in the auxilliary section. Newbie drivers going from an "X" to an "O" pattern might find themselves tearing up transmissions, lol! The "O" shift patterns have since been discontinued in order to harmonize things. An RTX-14610 transmission would be overdrive but have the last 2 gears in the same position as the RT-14610. So what about the "X"? The X denotes an overdrive transmission with a direct drive shift pattern. But overdrive transmissions were offered with the last two gears positions reversed.įor example, an overdrive RTO-14610 transmission manual would have 9th gear in the lower right hole and 10th gear in the upper right hole whereas the direct RT-14610 transmission would have those gears in their regular positions. Direct transmissions had the pattern we're typically familiar with, the 2nd to last gear being in the upper right hole and final gear being in the hole below. But there were also different shift patterns. Overdrive transmissions had "O's" in the name, such as RTO-14610 whereas the direct drive version of the same transmission would have just "RT". O and X, they're not just for hugs and kisses ![]() Lets look at a few changes and specific transmissions from years ago. Today you can get an autoshift 18 speed when 30 years ago the only way you could get 18 speeds was with a 2 stick transmission. Like trucks and engines, transmissions have changed with the industry.
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