Hurth Transmission Oil [E35-3]

[Dave G.]

Definitely suck it out through the fill/dipstick hole. I haven't even tried to remove the drain plug and hopefully won't have to anytime soon !

 

[nquigley]

Thanks! I'm hoping to do it this weekend.

 

[Prairie Schooner]

Today I pulled the transmission dipstick for my first time. It's the original Hurth. A mechanic (allegedly) changed the oil in 2022 but it's long overdue. The 'stick' looks different than the illustration in this document published elsewhere on this site.



This looks longer than above. Does it look right to you?


Thanks,
Jeff

 

[jtsai]

Yes, it looks about right. I changed the fluid in December.

 

[G Kiba]

The 30W motor oil in my Hurth is still working flawlessly! This is my 5th year and not so much as a slip, leak, or strange sound. The only thought about the transmission I have comes after reading these posts! BTW, I did pick up a used Hurth for $300 just in case. For now the plan is to see how long it keeps going. For historic presupposes, the reason I switched to 30W was severe slipping in forward. The oil immediately solved the problem and here we are 5 years later. I have change the oil every season and it is clear to light amber in color.

 

[s/v First Light]

So I am to be condemned for the fact that we have owned our boat for three seasons, and I have not changed the transmission oil. This is due to two facts:

1. The amount of boat yoga to get to our drain plug is daunting, in fact I am not sure if I can reach it without taking the heat exchanger off the engine. The hot water tank prevents me from getting to it from the aft lazarette.

2. I can’t seem to find out what oil I should be putting into this thing, and have read about Hurth HBW failures on this forum and am terrified of destroying ours with the wrong oil. Right now it just works, and that is good...

I see in the manual it says “Type A” transmission fluid. I have discussed this with basically every car parts place in the area, several who told me I was nuts, there was no such thing, one who told me to use the GM “anything” fluid, and one who finally relented, looked in his computer, found “Type A”, grunted about the fact that that was the darndest thing, and then said the didn’t have any in stock in the whole country, and it must have been replaced with something, but he couldn’t tell me what. So what type of fluid are people running here in their Hurth transmissions? I figured I need to relent at this point, and actually give the transmission some TLC.

My 1987 Ericson 32-3 has a HURTH HBW50 transmission. Several seasons ago it began slipping while engaged in forward. After doing some research I found that Ford Type F ATF has a higher gripping ability. I drained the current lubricant completely and then added Ford Type F ATF (it has stopped the slipping for the past 3 seasons). The Hurth dipstick below the fill port plug must be carefully watched in order not to overfill.

 

[gabriel]

According to previous post on this thread, the recommended type A atf was non existent but it can be found here on Amazon:

https://www.amazon.com/ABRO-Transmission-Economical-Formulated-Lubrication/dp/B09VTDLMZC/ref=asc_df_B09VTDLMZC?mcid=d91b0fcd37863246a9b755915124c821&hvocijid=12254398804538528050-B09VTDLMZC-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw=g&hvrand=12254398804538528050&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031447&hvtargid=pla-2281435181218&psc=1

As a pure base oil without any additive package, I would guess that straight 30 is a good substitute.

 

[Kenneth K]

Yeah, I think it's funny that they spec ATF at all for the Hurth. It's a manual transmission:

"Gear oil and transmission fluid are both lubricants for vehicle transmissions, but they are not interchangeable and are designed for different types of transmissions. Gear oil is typically used in manual transmissions and differential systems, while transmission fluid (also called ATF) is used in automatic transmissions. Gear oil has a higher viscosity (thicker) than transmission fluid and is designed to withstand higher pressures and temperatures."

I've been thinking of switching over to 30W motor oil or a gear oil this year, just as a preventive measure.

 

[gabriel]

Yeah, I think it's funny that they spec ATF at all for the Hurth. It's a manual transmission:

"Gear oil and transmission fluid are both lubricants for vehicle transmissions, but they are not interchangeable and are designed for different types of transmissions. Gear oil is typically used in manual transmissions and differential systems, while transmission fluid (also called ATF) is used in automatic transmissions. Gear oil has a higher viscosity (thicker) than transmission fluid and is designed to withstand higher pressures and temperatures."

I've been thinking of switching over to 30W motor oil or a gear oil this year, just as a preventive measure.

Typical automotive gear oil is thinner than motor oil.

 

[Kenneth K]

Didn't know that....

I thought oil weight (viscosity index) was a uniform measure. Apparently, it's not.

Apparently 30W motor oil is equivalent to 85W gear oil.

 

[Dave G.]

ZF the German company who owns/built the Hurth trannies for our sailboats has an extensive list of acceptable fluids. See attached for reference, find the trans then go to fluid list, 04D I believe. I used Mobil Delvac 1 as my local auto parts had that in stock but there are other options. Could not find any reference for Dexron fluids as acceptable but may be because the earlier Dexron fluids are no longer manufactured ?

 

[peaman]

Yeah, I think it's funny that they spec ATF at all for the Hurth. It's a manual transmission:

In automotive automatic transmissions, as well as our boat transmissions, friction clutches are used to shift from one gear to another. That differs from a basic automotive manual transmission where nothing slips, but instead, gears, or dogs, are moved to engage or disengage gears while a separate clutch is needed to allow smooth shifting.

 

[Kenneth K]

In automotive automatic transmissions, as well as our boat transmissions, friction clutches are used to shift from one gear to another. That differs from a basic automotive manual transmission where nothing slips, but instead, gears, or dogs, are moved to engage or disengage gears while a separate clutch is needed to allow smooth shifting.

So, it's a one-speed automatic transmission--if it were a manual it would need a manual clutch. Thanks.

 

[ConchyDug]

Would the gear oil used on outboard engines be acceptable? It's essentially the same type of gearbox. ATF Dex II is tough stuff we used it on helicopter transmissions. I think the ATF was used for it's resistance to foam up could be a similar reason on the Hurth.

 

[peaman]

So, it's a one-speed automatic transmission--if it were a manual it would need a manual clutch. Thanks.

I would call it a two-speed transmission for forward and reverse. Common gear boxes have two clutches, one for each gear, and both operated manually. This short video shows how it works.

 

[Prairie Schooner]

I would call it a two-speed transmission for forward and reverse. Common gear boxes have two clutches, one for each gear, and both operated manually. This short video shows how it works.

I loved that video so much that I dug further and found this. Perhaps you didn't post this one because it's kind of long, could have been more tightly edited. Though I do find the presenter charming.

 

[Kenneth K]

I would call it a two-speed transmission for forward and reverse. Common gear boxes have two clutches, one for each gear, and both operated manually. This short video shows how it works.

Yeah, great video. I get the gist of ICE and gas turbine engines. I even once owned a rotary (Wankel) engined Mazda. But transmissions have always been a mystery to me.

 

[Prairie Schooner]

I loved that video so much that I dug further and found this. Perhaps you didn't post this one because it's kind of long, could have been more tightly edited. Though I do find the presenter charming.

At 13:30 he begins to uncover the Hurth clutch plates and talk about how those work.

 

[peaman]

I loved that video so much that I dug further and found this.

That's a good one for us gear heads. One thing to watch for in both videos is the way the clutches are operated. there are springs and detents that cause the mechanism to be happy in exactly three positions: forward, neutral, reverse, and never in between. If the clutch is used without being fully in gear, there is a good chance of slipping which will quickly devolve into an unusable gear. When the shift cable is set up, it is important that in any of the three positions, there is some slight play in the cable at the transmission. You should be able to wiggle the shifter a bit before feeling the resistance of actually shifting gear.

 

[nukey99]

I have a friend who made the mistake of putting ATF fluid in Walter V drives and both of them failed due to incorrect lubricant. On our old powerboat with twin cummins 435's we had ZF transmissions and if I memory serves we ran 30w transmission oil in them. It pays to check.