17 October 2018 at 22:40 #52897
Hopefully someone has an answer to this question(s). Perhaps an oil technologist is a forum member?
I have just changed the oil on a T8 gearbox using EP90 API GL5 spec which is one of the recommended gearbox lubricants in the clubs M45 Manual (it was also the preferred gearbox lubricant of the late great Phil Ridout) There is I believe no longer a problem with EP oils attacking yellow metals in a gearbox as was the case when it contained sulphur around 15 years ago.
Back to the question, having run the engine I removed the gearbox top cover to find the oil was heavily frothed, bubbles everywhere and took about 20 minutes to settle in the bottom of the gearbox. There was no contamination of different oils as the change was like for like.
The questions are whether this frothing is something EP oils are prone to doing and whether in itself it has any detrimental effect?
Opinions, experience or reassurance welcomed
MarkStephen Matthews18 October 2018 at 18:02 #52902
Mark, In the early days of M45 ownership I also tried EP90 in the gearbox, I guess 20 years ago now. Having asked many gurus I changed to engine oil and other than it was cheaper and easier I have found it entirely satisfactory – I know I haven’t answered your question on EP90 oil froth, unfortunately I studied low film lubrication in high speed bearings, which was fascinating but I can’t recall the conclusions now!
Hope you are enjoying “Cooke’s” M45″. Stephenh1418 October 2018 at 18:31 #52903
Another oil to consider might be a synthetic gearbox oil, which is certainly available in 90 grade. I’ve used this in the transmission of my 205 CTi since I bought it in 2003, and indeed the previous owner also used it. This I would think more suitable for a gearbox intended to run on gear oil. I say this because the later G10 is designed to use engine oil, so take care that your engine oil advice was not intended for those later gearboxes. The synthetic oil, whilst being the correct grade, is substantially lighter in consistency, so will lubricate more thoroughly and offer far less drag.
Laurencebill19 October 2018 at 08:43 #52906
In case it helps I have also observed the sort of “frothiness” you refer to in my old M45 and also LG45 gearboxes and I don’t think it is a problem.
In my humble opinion I would have thought that EP90 was a bit thick – particularly when the car was cold.
I have always used engine oil in my T8 and G9 gearboxes and never found any problem.Colin M3422 November 2018 at 21:23 #52936
I have just finished putting a brand new set of club gears and shafts into my M45 gearbox.
Ouch yes it was expensive but seeing as I contributed to a almost new VW Sirocco as a 21st birthday present for my daughter, I don’t feel that guilty. After all, sadly, I now have dead parents….
For various reasons I visited the manufacturer of the Club gears and had a most satisfactory session with them, one outcome of which is that I use SAE 30 engine oil PLUS Molyslip 2001G oil & Metal Treatment. The critical lubrication factor seems to be to have oil going into the bushes whilst the Moly coats the gears nicely.
The box sounds lovely and my daughter is a smart young lady round town in her sports car.
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