Eaton Fuller 13 speed shift pattern: what the 21756 label shows
The 21756 decal is printed for the RT-6613 only (the label backing reads "Models: RT (ONLY) 6613"). The RT-6613 is the older style 13-speed: a five-position H-pattern with two ranges plus a deep reduction (Lo-Lo) selector on the knob, rather than the range-and-splitter layout used on later 13-speeds. Reading the label from the driver's seat:
| Lever position | Low range | High range | Deep reduction (Lo-Lo) |
|---|---|---|---|
| Top left | R | R | R |
| Top center | 2 | 7 | LL2 |
| Top right | 4 | 9 | LL4 |
| Bottom left | 1 | 6 | LL1 |
| Bottom center | 3 | 8 | LL3 |
| Bottom right | 5 | 10 | LL5 |
The label's printed progressive sequences are LL1-LL2-LL3-1-2-3-4-5-6-7-8-9-10 (thirteen forward steps). Upshifting: start with the range selector down, shift 1-2-3-4-5, raise the range selector, then shift 6-7-8-9-10. Downshifting: 10-9-8-7-6, move the range selector down, then 5-4-3-2-1. Pre-select range shifts, never change range while moving in reverse, and start the engine in neutral.
How the range and splitter work on an RTLO / RTO 13 speed
Most 13-speed trucks on the road today run an RTLO or RTO model, and those use a different pattern: Lo, 1, 2, 3 and 4 in low range, then 5, 6, 7 and 8 in high range with each gear split by the splitter button (H and L positions), which is what makes thirteen forward speeds. The splitter may be shifted in 5-6-7-8 only, and you must not range-shift with the splitter in H. Upshift Lo-1-2-3-4, raise the range selector, then 5-6-7-8; downshift 8-7-6-5, range selector down, 4-3-2-1-Lo. That layout is printed on the Eaton Fuller 4300764 RTLO 13 speed shift pattern label, and the matching knob-top insert is the 5586113 13 speed shift knob medallion. The RTO-6613 has its own deep-reduction decal, Eaton Fuller 21817.
How to shift an Eaton Fuller 13 speed
RTLO and RTO 13 speeds use the lever positions printed on the 4300764 13 speed shift pattern label. The range selector on the front of the knob picks low or high range, and the splitter button on the side picks the L or H half of gears 5 through 8.
| Lever position | Low range (selector down) | High range (selector up) |
|---|---|---|
| Top left | R (reverse, low) | R (reverse, high) |
| Bottom left | LO | No high range gear |
| Top center | 1 | 5L, 5H |
| Bottom center | 2 | 6L, 6H |
| Top right | 3 | 7L, 7H |
| Bottom right | 4 | 8L, 8H |
- Start the engine with the transmission in neutral and the range selector down.
- Upshift through the low range: LO, 1, 2, 3, 4. Leave the splitter in L; a 13 speed does not split the low range.
- Raise the range selector before you move the lever out of 4, then shift to the 5 position, which is the same slot as 1.
- Work up through the high range: 5L, 5H, 6L, 6H, 7L, 7H, 8L, 8H, moving the splitter to H for the upper half of each gear and back to L for the lower half.
- Downshift in reverse order: 8, 7, 6, 5, move the range selector down, then 4, 3, 2, 1, LO. Put the splitter in L first, because the label says never to range shift with the splitter in H.
The label adds three rules: pre-select every range shift, never change range while moving in reverse, and put the transmission in neutral before starting the engine. The knob that carries the range and splitter controls on this family is the S-2578 13 speed shift knob, and every unit we carry is listed in our Eaton Fuller 13 speed transmissions category. Running an 18 speed instead? See the Eaton Fuller 18 speed shift pattern.
Which 13 speed shift pattern label fits your transmission
| Transmission model | Pattern type | Shift pattern label |
|---|---|---|
| RT-6613 | Range + deep reduction (Lo-Lo) | 21756 (this page) |
| RTO-6613 | Range + deep reduction (Lo-Lo) | 21817 |
| RTLO-16913A, RTLO-18913A, RTLO-20913A, RTLO-14613B, RTO-14613 and other RTLO / RTO / RTOF / RTOX / RTOXF 13-speeds | Range + splitter | 4300764 |
Your model number is on the data tag on the passenger side of the unit; if it is unreadable, call us with the TA or serial number. Browse every unit in our Eaton Fuller 13 speed transmissions category.
13 speed shift knobs and air line kits
The genuine S-2578 13 speed shift knob with medallion and the A-6913 13 speed shift knob master valve are the two knobs that fit the RTLO / RTO 13-speed family, and both are available as S2578-KIT and A-6913-KIT bundles with the ALK1 air line kit.
13 speed shift pattern questions
What is the difference between a 13 speed and an 18 speed?
Both use the same lever positions and range selector. On a 13 speed the splitter works only in 5 through 8, so the low range has five steps (LO, 1, 2, 3, 4) and the high range has eight (5L through 8H). On an 18 speed the splitter works in every lever position, so LO and 1 through 4 split too. Compare the two layouts on the 18 speed shift pattern page, or shop Eaton Fuller 18 speed transmissions.
Can you shift a 13 speed like a 10 speed?
The lever work is similar: you run the H pattern in low range, flip the range selector, and run it again in high range. The difference is that a 13 speed has a separate LO position, four lever gears per range (1 to 4, then 5 to 8), and a splitter that adds a half step to each high range gear. Leave the splitter in L and the box steps LO, 1, 2, 3, 4, 5, 6, 7, 8; split 5 through 8 when the load needs closer steps.
What are common problems with an Eaton 13 speed?
A range or splitter that will not shift is most often an air problem: an air valve, the air filter regulator or an O-ring, rather than the gears. Check the knob and the air lines first. The S-2578 knob and the ALK1 air line kit cover the in-cab side, and our semi truck transmission guide walks through the rest.
Part details
| Part number | 21756 (also written FUL 21756, 3088-21756, ZBF21756) |
|---|---|
| Brand | Eaton Fuller |
| Type | Shift pattern instruction label / decal, peel-and-stick |
| Application | Eaton Fuller RT-6613 13-speed transmission (RT only) |
| Pattern | 5-position H, low / high range, deep reduction Lo-Lo (LL1-LL5) |
| Size | Approximately 12 in. x 12 in. |
- 3088-21756
- ZBF21756
Features
Shift pattern instruction label for Eaton Fuller 13-speed RT-6613 transmissions
Manufacturer part number 21756
Approximately 12 in. x 12 in.
Genuine Eaton Fuller part
Tech Specs
- Part Number: 21756
- Application: Eaton Fuller 13-Speed RT-6613 Transmission
- Type: Shift Pattern Instruction Label / Decal
- Dimensions: approximately 12 in. x 12 in.
