Installation Tips New & Rebuilt
ZF And Hurth Marine Transmissions
This section contains information specific to ZF and Hurth marine transmissions and is intended to be used with
the information supplied on the Basic Installation Tips page.
A. ZF and Hurth Manual Marine Transmissions:
"Manual" when used in marine transmissions referrers to manually operated mechanical shifting as
opposed to hydraulically operated shifting. ZF model numbers include an "M" to indicate a manual
transmission. Hurth used a "HBW" prefix for manual units.
1. The shift lever cable adjustment on all manual units is critical. Since there is on a neutral detent care
should be taken to insure that the bridge shift lever is in neutral when the transmission shift lever is in
neutral. The shift throw in forward and reverse should be approximately the same but the lever MUST
move past the "click point" in order to properly engage the forward and reverse clutch assemblies.
Failure to fully engage the clutch assemblies will result in rapid clutch wear and clutch failure.
2. The aluminum cases as well as the input bearings of both Hurth and ZF manual transmissions can be
ruined by wobble induced into the input shaft by a defective damper plate. Careful inspection of the
damper plate is required before the installation of a manual transmission. If in doubt, replace it.
B. ZF and Hurth Hydraulic Marine Transmissions:
ZF marine transmissions that DO NOT contain an "M" in the model number and Hurth transmissions that
have a "HSW" prefix or transmissions with an "IRM" prefix have hydraulically activated clutch assemblies.
1. ZF and Hurth hydraulic marine transmissions use a high pressure, 300 PSI or higher, in their fluid cooling
loop. High Pressure fluid coolers having a rating or 375 PSI must be used. Use of "standard", 150 PSI
low pressure coolers will result in cooler blowout and transmission failure. See out Accessories page
for High Pressure coolers.
2. Check to insure all hoses are rated for at least 375 PSI.
3. When changing fluid filters on ZF and Hurth transmissions equipped with them be sure to always change
the o-rings supplied with the filter. Apply a light coating of grease to the o-rings. These filters are on the
input or vacuum side or the fluid pump. A suction leakage around the filter cap will result in reduced or no
hydraulic pressure. Check for suction leakage by pouring a small amount of ATF around the edge of the
cap. Fluid will be sucked into the case if there is any leakage present.
Call us if you have any questions about the installation of your ZF or Hurth transmission.