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Transmission - New Replacement 12M

Part #: Z4377


This transmission is manufactured by ZF as a replacement for the original Hurth transmissions originally installed on most Universal Diesel engines. Just in case you are unfamiliar with the name, ZF supplies transmissions to Mercedes and BMW as well as drive systems for super tankers.




Smaller engines were originally equipped with the Hurth HBW50 transmission. Larger engines used the HBW100 transmission. Unfortunately, the smaller transmission has been discontinued entirely. The closest replacement transmission, ZF's 10M is a very close replacement for either but due to their limited production, they are more expensive. The replacement transmission, 12M above, is ZF's larger, more common unit and is therefore offered at a lower price than the 10M that replaced the HBW100.Boats that may be able to use this transmission include:
• Capri 26
• Catalina 25
• Catalina 27
• Catalina 28
• Catalina 30
• Catalina 310
• Catalina 34
• Catalina 350
• Catalina 36
• Catalina 38
There may be others as well, and not all of the above listed boats can use this transmission. Check the model of your engine to be sure.

Engines that originally used the HBW50 transmission:
• M-5411
• M-12
• M2-12
• M-18
• M-320
• M-25
• M-25XP
• M-25XPB

Engines that originally used the HBW100 transmission:
• M-5424
• M-30
• M-35
• M-35B



Critical Dimensions (see "Technical Support" below for detailed specifications)
• Front to back (L + L3) : 207mm (8.15")
• Output shaft drop from crank: 72mm (2.83")
• Reduction ratio: 2.14:1

Important differences when compared to HBW 50 transmission
• Front to back (L + L3) : +37mm (+1.46")
• Output shaft drop from crank: +10mm (.39") Will require raising the engine 10mm
• Reduction ratio 12M vs HBW 50: 2.14:1 vs. 2.05:1

Important differences when compared to ZF 10M transmission
• Front to back (L + L3) : +12mm (.47")
• Output shaft drop from crank: +10mm (.39") Will require raising the engine 10mm
• Reduction ratio 12M vs 10M: 2.14:1 vs. 2.05:1

1) In most cases the extra length and drop of this transmission compared to the original HBW50 or HBW100 will not cause an issue. But in some boats, the Catalina 28 MkII and Catalina 30 for example, the extra length and drop makes installation almost impossible. It is always your responsibility to compare all dimensions included below under "Technical Support" titled ZF 12M Transmission Specifications before ordering to ensure this transmission will be a proper fit to your boat.

Even though due to their extremely limited production the Z4099 (ZF 10M) transmission is ridiculously expensive, it may be the wiser choice when fitting into the very limited space available in some Catalina models.

2) The transmission has been tested and then drained of oil prior to shipment to avoid being classified as "hazardous material" due to flammable liquid inside. Be sure to add oil before using.

3) These transmissions are shipped from the factory to the West Coast on a pallet. They are then repackaged and boxed individually by the warehouse. Don't expect a fancy printed box. You may find a bit of residual oil in the box that has leaked from the breather tube during shipment.

4) Transmissions do not conform to the shipping table in the Shopping Cart. Additional shipping must be calculated. When you place your order we always call with a shipping quote before billing your card. For a quote in advance, just call 800/959-7245.

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