PRM 120 gearbox oil change

[MichaelG]

Hi all, my boat is fitted with a PRM 120 gearbox circa 2006. I wonder if anyone who has one of these boxes could tell me what oil should be used. The information I have found on the web is a bit contradictory, some saying Automatic Transmission Fluid should be used, other sources saying ordinary mineral motor oil. I think the ambiguity may well be caused by the manufacturer changing its own advice over the years.

Also, silly question time, is changing the oil as simple as draining from the drain plug and refilling via the screw out dipstick hole?

 

Many thanks, Michael.

[RLWP]

If it is a small, rectangular gearbox with a lever on the side, it's ATF.

 

yes, drain on the bottom, filler on the top

 

Richard

 

MORE: Like this, could be any colour:

 

Edited June 10, 2018 by RLWP

[Pie Eater]

My gearbox is the same as yours and I use ordinary engine oil. Draining is as simple as you say or you could pump the oil out with a Pela pump.

[RLWP]

2 minutes ago, Pie Eater said:

My gearbox is the same as yours and I use ordinary engine oil. Draining is as simple as you say or you could pump the oil out with a Pela pump.

Manual says ATF: http://www.prm-newage.com/media/File/PRM120.pdf

 

Incidentally, you get really weird effects if you put EP80 into one

 

Richard

[WotEver]

15 minutes ago, RLWP said:

Incidentally, you get really weird effects if you put EP80 into one

And you know this because...?

[RLWP]

3 minutes ago, WotEver said:

And you know this because...?

Because my customers do all sorts of peculiar things

[WotEver]

Well, it’s gearbox oil innit?

[Boater Sam]

Not really, its Extreme Pressure oil, designed for Hypoid helical cut  crownwheel and pinion differentials and final drives,

 

Out of interest, spill the beans, what odd things happen if you use it in a PRM 120?

[alan_fincher]

42 minutes ago, Pie Eater said:

My gearbox is the same as yours and I use ordinary engine oil. Draining is as simple as you say or you could pump the oil out with a Pela pump.

 

39 minutes ago, RLWP said:

Manual says ATF: http://www.prm-newage.com/media/File/PRM120.pdf

 

They did use to specify engine oil for the non-hydraulic boxes as well as the hydraulic ones.

Then they changed their minds.

So an old manual will specify engine oil in a 120, whereas a newer manual will say ATF.

I'm assuming the change is for a good reason, but also I suspect anyone who has historically used engine oil is probably not going to have too many issues.

[RLWP]

1 minute ago, Boater Sam said:

Not really, its Extreme Pressure oil, designed for Hypoid helical cut  crownwheel and pinion differentials and final drives,

 

Out of interest, spill the beans, what odd things happen if you use it in a PRM 120?

Well, one possibility is calling in an engineer because the gearbox slips

Just now, alan_fincher said:

 

 

They did use to specify engine oil for the non-hydraulic boxes as well as the hydraulic ones.

Then they changed their minds.

So an old manual will specify engine oil in a 120, whereas a newer manual will say ATF.

I'm assuming the change is for a good reason, but also I suspect anyone who has historically used engine oil is probably not going to have too many issues.

I was waiting for this post

[alan_fincher]

1 minute ago, RLWP said:

I was waiting for this post

 

And.............. ?

[RLWP]

Just now, alan_fincher said:

 

And.............. ?

Just what I said. A post like this turns up every time this subject is raised here

[MichaelG]

14 minutes ago, alan_fincher said:

 

 

They did use to specify engine oil for the non-hydraulic boxes as well as the hydraulic ones.

Then they changed their minds.

So an old manual will specify engine oil in a 120, whereas a newer manual will say ATF.

I'm assuming the change is for a good reason, but also I suspect anyone who has historically used engine oil is probably not going to have too many issues.

Hi all, thanks for the prompt replies. Yes, I think the contradictory advice found on the web probably is due to the changing advice from the manufacturers. I have no idea what has been used in the box upto now so I wonder if changing from motor oil to ATF or vice versa is likely to cause any issues?

Also next silly question, the advice found on the web from Newage that suggests ATF is used says to use ATF specified to Dexron 2 or 3. I see that there are various ATFs specified to Dexron 2 and 3 but they come in mineral, semi synthetic and fully synthetic variants?

 

Many thanks Michael.

 

[WotEver]

28 minutes ago, Boater Sam said:

Not really, its Extreme Pressure oil, designed for Hypoid helical cut  crownwheel and pinion differentials and final drives,

Yes I know... I was (attempting) being humorous. 

[Boater Sam]

Sorry I missed that, no smile and what is "innit" ?

[Wanderer Vagabond]

16 minutes ago, MichaelG said:

Hi all, thanks for the prompt replies. Yes, I think the contradictory advice found on the web probably is due to the changing advice from the manufacturers. I have no idea what has been used in the box upto now so I wonder if changing from motor oil to ATF or vice versa is likely to cause any issues?

Also next silly question, the advice found on the web from Newage that suggests ATF is used says to use ATF specified to Dexron 2 or 3. I see that there are various ATFs specified to Dexron 2 and 3 but they come in mineral, semi synthetic and fully synthetic variants?

 

Many thanks Michael.

 

This is the one I stick in my gearbox ( https://www.amazon.co.uk/Castrol-1848060-17135600-Transmax-Multi-Vehicle/dp/B004UAXL48/ref=sr_1_1/259-1382670-4456239?ie=UTF8&qid=1528668017&sr=8-1&keywords=castrol+transmax+dex+iii     )and it seems to work OK (tempting fate).

[rgreg]

I have a PRM 120 and rang the manufacturer with this question several years ago (so possibly old advice). They told me put in whatever oil I put in my engine, which I have done without issue since. However, if the recommendation is for ATF now I'll use this instead. I remove the oil by a manual suction pump through the dipstick hole.

[RLWP]

9 hours ago, MichaelG said:

Hi all, thanks for the prompt replies. Yes, I think the contradictory advice found on the web probably is due to the changing advice from the manufacturers. I have no idea what has been used in the box upto now so I wonder if changing from motor oil to ATF or vice versa is likely to cause any issues?

Also next silly question, the advice found on the web from Newage that suggests ATF is used says to use ATF specified to Dexron 2 or 3. I see that there are various ATFs specified to Dexron 2 and 3 but they come in mineral, semi synthetic and fully synthetic variants?

 

Many thanks Michael.

 

I doubt it makes any difference. These are very simple gearboxes with a sintered cone clutch. They seem to like the lower viscosity oils, apart from that I can't see it makes any odds. Remember, ATF (Automatic Transmission Fluid) is used in this very basic gearbox, and in highly complicated seven speed automatic gearboxes in cars. That's where the different specs matter

 

Richard

[bizzard]

A similar situation with the oil in early Lister LH150 and I think the manual boxes. Originally they prescribed ordinary 30 grade engine oil in them, ''no hellically cut gears in them, although you still get teeth rub of course with straight cut gears''.  A few years later, late 1960's I think, was changed to Hypoid 90- EP 80/90, presumably to quieten it a bit when in astern gear, or to raise the oil pressure a bit with the thicker oil, but that could have been done by adjusting the relief valve.  The reduction gear with hellically cut gears of course always used Hypoy oil.  I rember some old pre war cars using Hi Press oil in the rear axle '' EP 160 or so. When it was cold you could feel the drag, pop the car into neutral whilst going along and the drag was enough to quickly slow the car without using the brakes, Hi-Press oil smelt rather nice, like almonds, hypoy stinks like cats pee.

[WotEver]

Just fill the gearbox with sawdust, that’ll quieten it down. 

[bizzard]

2 minutes ago, WotEver said:

Just fill the gearbox with sawdust, that’ll quieten it down. 

Oh! Mr Daley.

[boots]

We had a problem a couple of years ago with our PRM 120  and spoke to the manufacturer who explained that we should only use ATF, and that the problem we were experiencing could have been due to using engine oil in the past. 

 

For info, the issue we had was that when selecting reverse, it did not immediately engage x rather it took a few seconds before the drive engage - over time this got worse until eventually we could not engage reverse. (Sadly, for us the issue wasn’t related to the oil being rather more terminal and we needed a new box.j but just to reiterate they were categorical about using ATF.

 

Martin

[AndrewIC]

My relatively new 120 has a drain plug with a magnet to collect crud (someone will no doubt be along shortly with a more technical term), so if you do drain with a pump, remove the drain plug after and give the magnet a clean, 

[RLWP]

8 hours ago, AndrewIC said:

My relatively new 120 has a drain plug with a magnet to collect crud (someone will no doubt be along shortly with a more technical term), so if you do drain with a pump, remove the drain plug after and give the magnet a clean, 

I wonder what it would collect? The cone clutch is made of bronze, as is the operating wedge

 

Richard

[Chewbacka]

5 hours ago, RLWP said:

I wonder what it would collect? The cone clutch is made of bronze, as is the operating wedge

 

Richard

Bits from the bearing surfaces?