ATF effect on gearbox that should have engine lube oil?

[LittleSister]

What would be the effect on a yacht engine gearbox of putting in ATF instead of the engine lube oil it should be?

The background to this is I had a problem with the gearbox (BW7 on a Bukh 36) of a then new to me boat. It would go in and out of gear easily when engine stopped, into gear easily when engine running, but very stiff to get out of gear (both forward and reverse) when engine running (i.e. when prop and gearbox loaded), such that frequently it would take so much force to pull it out of gear I'd shoot past neutral and crash into the opposite gear with a horrible crunch, and then have the same problem getting out of that new gear. (All rather stressful in a crowded marina!)

I'd checked the gear lube level was correct, and initially thought (I can't remember why) the problem was something to do with the controls, the cables, or the contraption that combines/changes over the two control stations (wheelhouse and cockpit)l. I tweaked those and changed one of the cables with no significant effect. Having studied the gearbox drawings and asked on here, I came to the conclusion it was beyond me, I would have to change the gearbox, and bought a second hand one.

The boat has since been out of the water for several years due to life calamities, and coming back now to recommission it I drained the oil from the gearbox in preparation for removing and replacing it. The oil I extracted is dark brown, but has a distinctly red hue to it. I would have thought that I would have changed the gearbox oil when I had the boat in commission, but it was a bit of a fraught time for me, I can't remember actually doing so, and struggle to imagine that the engine oil I would have used would have darkened that much given the relatively few miles I was able to do in it (though it has stood unused for several years since).

If the previous owner had mistakenly put ATF in the gearbox, instead of engine lube oil, could that be the cause of my problem getting out of gear?

 

[penberth3]

What would be the effect on a yacht engine gearbox of putting in ATF instead of the engine lube oil it should be?....

The worst case is you destroy all the seals. That might happen quickly, it might take some time, it depends on the materials.

 

[Leslie frank]

Atf is very thin, like water, so it doesn't coat very well. I would have thought you would have had more wear in the components if used a great deal. It also smells quite different which might give you an idea if it has been that inside

 

[doug748]

The old farts on here will recall that there was always indecision about what to use on the old Petter gearboxes. There is no doubt that the engine makers specified ATF but the actual manufacturers of the gearbox always recommended a thicker oil. Some did one thing, others another.

It probably did not matter as long as you were consistent and changed it regularly. I would follow what is in the book.

.

 

[pandos]

With regards to your original problem. My friend had a similar issue, it turned out that the gear lever was not throttling down properly so that in effect he was trying to to change gears at high revs. The key to the discovery was that with the engine stopped it was easy to shift.

After a replacement gearbox and many hours of stressful sailing the simple fix was done.

 

[LittleSister]

Any views on whether the it might result in -
- clutch plates sticking together, or
- increased friction between sliding parts (whether that be clutch plates as pressure is taken off them, or gears being slid along their shafts).

I am primarily interested in whether the gearbox/clutch might operate differently with the correct oil (assuming it had the wrong oil before).

I am currently in a quandary as to whether to -
- launch the boat with the existing gearbox, in the hope my problem might go away or reduce with the correct/fresh oil (which would also save a lot of time and aggravation while the season is slipping by) but with the risk that I shall be stuck with the same problem for at least another season; or
- change the gearbox, hoping that second-hand one works OK, and not knowing whether or not the original one was any good for selling on.

 

[Mistroma]

I seem to remember someone putting ATF in a Kanzaki KM35P gearbox and it caused the drive to slip. So it can happen. However, that unit has cones and I think they are prone to wear causing slippage. I think the ATF caused total loss of drive pretty quickly. I don't think the BUKH design is similar and OP has had that oil on for quite a while. Seems likely that it's less of an issue with BUKH.

 

[LittleSister]

The BW7 is a ZF brand gearbox (and was fitted to a variety of engines) if that makes any difference.

 

[ducked]

Any views on whether the it might result in -
- clutch plates sticking together, or
- increased friction between sliding parts (whether that be clutch plates as pressure is taken off them, or gears being slid along their shafts).

I am primarily interested in whether the gearbox/clutch might operate differently with the correct oil (assuming it had the wrong oil before).

I am currently in a quandary as to whether to -
- launch the boat with the existing gearbox, in the hope my problem might go away or reduce with the correct/fresh oil (which would also save a lot of time and aggravation while the season is slipping by) but with the risk that I shall be stuck with the same problem for at least another season; or
- change the gearbox, hoping that second-hand one works OK, and not knowing whether or not the original one was any good for selling on.

Cant you test it on the hard, making appropriate engine cooling improvisations if necessary?

If not, with the incomplete info you have, I'd be inclined to go with the gearbox you've got, rather than do a possibly uneeded gearbox swap. You might try and get an "expert opinion" on what oil its got in it, possibly even sending off a sample for analysis. If its ATF I doubt its done much harm but it might interfere with normal operation.

ATF is generally high detergent but relatively low viscosity, though not low viscosity relative to "modern" engine oils, The manufacturer story on "modern" engine oils is generally that they dont cause additional wear, but then (a) they have additional boundary layer additives, and (b) they would say that, Mandy Rice-Davies stylee

 

[LittleSister]

Cant you test it on the hard, making appropriate engine cooling improvisations if necessary?

I can't test in on the hard, because I can't load up the prop and gearbox.

Yes, I'm hoping to get an opinion from an engineer as to whether it's ATF, but even if it is, I still won't know if the correct lube will make a difference.

Bu thanks for your suggestions and info.

 

[Boater Sam]

Have you disconnected the cable at the gearbox and manually moved the naked lever to eliminate the conglomeration of cables with a two station control?
That should be your first step as two station controls are renown for binding up. at one end or the other.
ZF do specify ATF type oil but in my experience it makes little difference over engine oil.

 

[seeSimon]

Fwiw...

Beta marine specify ATF lube in their Technodrive ("Italian Twin Disc") Sea Prop sail drive legs. They appear to me to be fairly conventional units?

Even decent quality Dextron 2 ATF fluid is cheap/easy enough to change every winter.

 

[seeSimon]

Cant you test it on the hard, making appropriate engine cooling improvisations if necessary?

If not, with the incomplete info you have, I'd be inclined to go with the gearbox you've got, rather than do a possibly uneeded gearbox swap. You might try and get an "expert opinion" on what oil its got in it, possibly even sending off a sample for analysis. If its ATF I doubt its done much harm but it might interfere with normal operation.

ATF is generally high detergent but relatively low viscosity, though not low viscosity relative to "modern" engine oils, The manufacturer story on "modern" engine oils is generally that they dont cause additional wear, but then (a) they have additional boundary layer additives, and (b) they would say that, Mandy Rice-Davies stylee

Agree, i find many modern lube oils frighteningly "thin".
I believe I have a reasonable understanding of viscosity modifiers, additives etc..but am no chemist.

As an old lag of an engineer, I remain deeply suspicious of marketing hype, and these days in particular, business/financially driven "specifications".
Eg long life services on new cars. Ideal if you're leasing a fleet and can keep service costs down, ideally kicking the service costs down the road to the second owner...but never mind the long term effect on the durability of the machine - that's not your problem/expense as long as it lasts the lease?
My last leased new car, a reasonably complex VW 4x4 diesel auto, didn't need any servicing for the first 20k miles I recall? That's what it got..level checks only.
I recall similar early diesels had a 5k service interval...that's only 20 years ago. service costs were very significant and also very inconvenient, visiting the garage almost monthly at some points.

...and then there's the need to be seen to reducing "emissions " which in the short term are helped by reducing drag within the machine....again no consideration of long term durability.


Anyway OP...surely you can detect the difference between ATF and gear oil? Smell?
Get a sample of the used oils and use ALL your senses to compare them?
Ask a human engineer?

 

[Refueler]

Little story :

Capri 2.8i ..... was prone to gearbox failure on the 5 speed versions ... they were first filled with heavy grade Gear oil .. which basically within warranty period - the gearbox whine would start ....
Into Dealer ... first days of the 2.8i - they would change the gearbox ... but then some bright spark in Ford decided that solution was to change to same engine oil as in the engine ... so change box + oil. Whine comes back ... what to do ??

Fords eventually decided to fill the gearboxes with ATF instead ... which delayed the whine .... note - DID NOT stop it ... just knocked enough down the road ......

How do I know ? I owned 2 of them ... both suffered it ... a Pepper Pot Wheels 5speed and the later 2.8i special again 5 speed. I wanted a 4speed first version - but none were available locally at the time.
The info was given me by a Ford Dealership I was friendly with ..... and why ? Ford had left out one feed in the box that allowed one shaft to run dryer ... 3rd party gearbox people who renovated such boxes - such as Heathrow Gearboix Company - used to modify the boxes to include an exatr oil feed to cure it.

But anyway .... the point is that Ford considered it fine to go through from heavy gear oil to engine oil to ATF in same box.

Despite my job - I do not comment on + / - of ATF - as its a different ball game altogether compared to general Lub Oils and Fuels. Even I defer to manuals / those who deal in the stuff.
What I do hear from them - the days of Power Steering / ATF / Hydraulic Oil being similar are long gone !

 

[TSB240]

The BW7 is a ZF brand gearbox (and was fitted to a variety of engines) if that makes any difference.

Bukh Hand Book says for ZF-marinegear box:

Lubricating oil quality - API, CC or CD, MILL-L-46152
Lubricating oil viscosity - SAE 15W/40

My boat also has a zf box and it has a ZF label on it saying ATF oil only.

The handbook for it says use same oil as engine!

I have taken the ZF label off.

 

[LittleSister]

Bukh Hand Book says for ZF-marinegear box:

Lubricating oil quality - API, CC or CD, MILL-L-46152
Lubricating oil viscosity - SAE 15W/40

My boat also has a zf box and it has a ZF label on it saying ATF oil only.

The handbook for it says use same oil as engine!

I have taken the ZF label off.

 

[rotrax]

The worst case is you destroy all the seals. That might happen quickly, it might take some time, it depends on the materials.

Why would a specific ATF oil, designed for hydraulic gearboxes, destroy seals? Hydraulic gearboxes rely on synthetic rubber seals for operation, the ATF oil is made to give them a long, trouble free life. Ordinary lip seals are fine with ATF oils too. From 60 years direct experience.

Before motorcycle front fork oils were available with varying viscosities, I would mix my own from ATF and straight oils. Never had a seal fail, even in the IOM during six laps of the TT course.

 

[LittleSister]

With regards to your original problem. My friend had a similar issue, it turned out that the gear lever was not throttling down properly so that in effect he was trying to to change gears at high revs. The key to the discovery was that with the engine stopped it was easy to shift.

After a replacement gearbox and many hours of stressful sailing the simple fix was done.

Do you remember how high the revs were?

Well, I started the engine today to check the tickover revs. Manual says it should be 800 - 1,000 rpm (I'm sure in another Bukh manual said 900 - 1,000 rpm, but no matter - just found it - the Operating Manual says 800-100 in the technical spec list, but 900-100 in the text .).

On start up it immediately settled down to a steady 1,050 revs (according to the tacho). I couldn't think that an additional 50rpm (i.e. 5% above spec) was going to make much difference, and anyway is probably within the tolerances of the tacho.

I left the engine running for maybe 10 minutes while I checked that the lever on the injection pump was returning all the way to its stop when the control lever is returned to tickover/neutral, which it did for both of the dual-station controls. I then noticed that the tacho was now reading about 1,260 rpm (i.e. about 26% too high, and 57% higher than the recommended minimum idling speed). I checked again, and the lever on the injection pump was still against the stop.

I wonder whether that is what has been causing my problem getting out of gear, and I'm now leaning towards retaining the existing gearbox, adjusting the tickover within spec, and using what the correct oil as specified by Bukh rather than the suspect lubricant that was in there.

But I am puzzled by the increase in tickover speed once the engine had been running a few minutes. While I can understand the engine getting 'looser' as more oil circulates and everything starts warming up, I would have assumed the governor would be controlling the fuel supply to compensate for that, and holding it at the idling revs set.

 

[pandos]

Do you remember how high the revs were?

Well, I started the engine today to check the tickover revs. Manual says it should be 800 - 1,000 rpm (I'm sure in another Bukh manual said 900 - 1,000 rpm, but no matter - just found it - the Operating Manual says 800-100 in the technical spec list, but 900-100 in the text .).

On start up it immediately settled down to a steady 1,050 revs (according to the tacho). I couldn't think that an additional 50rpm (i.e. 5% above spec) was going to make much difference, and anyway is probably within the tolerances of the tacho.

I left the engine running for maybe 10 minutes while I checked that the lever on the injection pump was returning all the way to its stop when the control lever is returned to tickover/neutral, which it did for both of the dual-station controls. I then noticed that the tacho was now reading about 1,260 rpm (i.e. about 26% too high, and 57% higher than the recommended minimum idling speed). I checked again, and the lever on the injection pump was still against the stop.

I wonder whether that is what has been causing my problem getting out of gear, and I'm now leaning towards retaining the existing gearbox, adjusting the tickover within spec, and using what the correct oil as specified by Bukh rather than the suspect lubricant that was in there.

But I am puzzled by the increase in tickover speed once the engine had been running a few minutes. While I can understand the engine getting 'looser' as more oil circulates and everything starts warming up, I would have assumed the governor would be controlling the fuel supply to compensate for that, and holding it at the idling revs set.

I don't remember but it wasn't noticably "racing" perhaps throttle back your engine to just above stall and see if that helps the changing issue...

His changing was perfect with the engine turned off...and that became the cure for a while...but not much fun when manoeuvering into a berth...

 

[LittleSister]

I don't remember but it wasn't noticably "racing" perhaps throttle back your engine to just above stall and see if that helps the changing issue...

His changing was perfect with the engine turned off...and that became the cure for a while...but not much fun when manoeuvering into a berth...

Thanks. That's encouraging. (Or at least I'll take apparent go omens where I can find them!)

My engine doesn't sound like it's racing at 1260, but it is quite a 'busy' sounding engine at any speed, and I hadn't even noticed its speed had increased since I'd started it, and only realised it had when I happened to glance at the tacho after i thought I was done with it.

Unfortunately, I can't check in advance whether it comes out of gear satisfactorily at a lower tickover speed, as the problem only arises under load - i.e in the water and in gear - and the boat is currently ashore.

Once it goes in the water - with either old gearbox or a second-hand replacement, I shall be stuck with the result for maybe a year until it is brought ashore again.

I am leaning towards launching with existing gearbox, tickover adjusted down, and fresh correct oil (while trying to tell myself this is not just because I want to avoid the time and aggravation of changing the gearbox!) .

I have a vague recollection one can get a 'tacho' app for mobile phones that uses its photo flash. I'll investigate that to try to verify the tacho readings.