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4-speed transmission by Samwel Supplies; fits 45”/750cc Flathead solo models 1947-1952; cast aluminum / steel; replaces OEM 33006-47; Europe; NOTE: These transmissions are designed for 1947→ shifter gates (1st gear backward); gross weight: 10.36 kg

Fully assembled, ready-to-install, 4-speed (!) transmissions for 1941-up 45 cui./750 cc Sidevalve Harleys.

It is a fact that while the engines seem to last forever, those worn, clunky transmissions can be a continuous source for trouble. Full restorations - and that’s exactly what is often required - are expensive and tasks for the real experienced only, so it is definitely worthwhile to consider a complete replacement. Especially when this replacement is not just a well functioning duplicate of the same old thing but a large improvement, too.

A real drawback with original 3-speed transmissions is the large gear ratio difference between 1st and 2nd, i.e. from 2.47 to 1.57:1 with a consequent big rpm drop. If you ever rode 2-up in the mountains you will know how annoying this can be. The 4-speed version with its extra gear is a vast improvement here because it allows you to stay in the power band much better for an overall riding performance unknown before. Additionally, all gears are machined from modern materials for higher strength and feature an updated tooth-design for smoother and quieter running. Solo machines, sidecar rigs and Servi-Cars - all likewise benfit from these features.

The 4-speed transmission comes completely assembled with all gears, shafts and covers installed for a quick, straightforward installation. It accepts your original primary drive with clutch and the chain sprocket with cover. It looks exactly the same as its 3-speed counterpart so nobody can tell the difference from its outer appearance. The only extra part required is a 4-speed shifter gate.

Stock 3-speed gear ratios:

1st - 2.47:1

2nd - 1.57:1

3rd- 1:1

4-speed gear ratios:

1st - 2.67:1

2nd - 2.03:1

3rd - 1.42:1

4th - 1:1

... more
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  • 45-852

    45-852 Shifter guide; fits Big Twin 1947-1965; 4 speed; steel, chrome-plated; replaces OEM 33789-47; gross weight: 190 g

  • 86-146

    86-146 Adjusting screw; for Transmission; fits 750cc 1929-1963; parkerized; length: 78 mm; thread: 3/8”-16; replaces OEM 34736-27; gross weight: 50 g

  • 94-900

    94-900 Oil by PanAm; SAE 50W; usage: engine / transmission; regular; Germany; gross weight: 960 g

See also:

  • HMB Shifter Ratchet for 750cc/45cui

    HMB Shifter Ratchet for 750cc/45cui This shifter mechanism basically works like a Ratchet Top of Big-Twin models: after each shifting operation all involved levers return to their home position ...

  • 12.7 mm Belt Drive Kits for 45” (750cc) Flatheads

    12.7 mm Belt Drive Kits for 45” (750cc) Flatheads Complete, smooth running belt drive kits for 45" models which eliminate the need for primary lubrication and thus the inevitable spot of oil underneath your ...

  • 4-Speed Conversion Kit 45”/750cc

    4-Speed Conversion Kit 45”/750cc A drawback with original 3-speed transmissions is the large gear ratio difference between 1st and 2nd, i.e. from 2.47 to 1.57:1 with a consequent big rpm drop. ...

Have any questions?

  • Our sales team will be glad to help out:
    Mondays - Thursdays 08:00-17:00 CET, Fridays 08:00-16:00 CET
    Phone: +49 / 931 250 61 16