Section : Gearbox

Clutch, gearbox, overdrive, propeller shaft.

Gearbox oil synthetic or not?

Posted By : Yan Holland, 07-May-2003, 10:58am

Have been browsing various websites and literature trying to find out if it is better to put a more modern fully synthetic multigrade oil in the gearbox or not. Multigrade oils appear to remove stiff gearchange problems when 'box is cold but I have concerns with the effect on the overdrive friction cone. Also GL5 spec has been known to melt copper washers!!! Anyone got any long term experience running a fully synthetic SAE 75W90 - GL5 spec oil in their 'box? Any suggestions would be appreciated.

Thanks folks,
Yan.

Have also found an item that suggests it is not advisable to put GL5 spec oil in the diff' because of the copper washer problem.

Followups :

Gearbox oil synthetic or not?

Posted By : Andrew Lewis, 08-May-2003, 01:24pm

My understanding is GL5 is fine for the gearbox but not for the diff (copper problem as you mentioned).
- Gearbox oil synthetic or not?
  
  Posted By : Nigel Gibbins, 08-May-2003, 08:15pm
  
  Doesn't the gearbox have two copper faced thrust washers on the layshaft?
  
  If so wouldn't GL5 melt them - melting, melting!
  
  NiG
  http://www.niginthecar.net
  - Gearbox oil synthetic or not?
    
    Posted By : Yan Holland, 09-May-2003, 01:51pm
    
    Sent an e-mail to Castrol with reference to the problem and got this reply back.
    
    The correct oil for your gearbox is indeed Castrol EP90 (GL4) which you should be able to buy locally, GL5 (non Castrol) spec can is some cases attack bronze/brass bushes, however Castrol long ago ceased using additives that do that. Another really good product would be Castrol Syntrax 75w/90 (part synthetic) it covers GL3/GL4 and GL5 specs and is one of few modern products suitable for early engineering requirements, again you should be able to buy this locally.
    
    I think that decides it really, Syntrax it is at around a tenner a litre from Halfords, should make the box more usable from cold by using the multigrade oil.
    
    Thanks for the replies and suggestions folks,
    
    Yan
    - Gearbox oil synthetic or not?
      
      Posted By : Nigel Gibbins, 14-May-2003, 08:15pm
      
      I can now safely admit I run syntrax in my competition cars gearbox, on the advice of my engineer. I have had not problems with it at all - and it should have broken by now if there was a problem. Looks, way too thin when your putting it in though but don't let that fool you.
      
      NiG
      http://www.niginthecar.net
      - Gearbox oil synthetic or not?
        
        Posted By : Yan Holland, 17-May-2003, 10:13am
        
        Aha a former closet user of Syntrax comes out! Only joking, it's good to know that someone has had put some running hours on a 'box running the stuff. I do have one final question though do you find the 'box is smoother when it's cold compared to a mono-grade EP90 oil? Or is it one of those imperceptable differences that no-one knows about?
        
        Cheers, Yan
        
        Gearbox oil synthetic or not?
        
        Posted By : Peter Boxshall, 17-May-2003, 11:54am
        
        I too am interested in the Syntrax oil for my gearbox which operates quite well (for it's type) when it is cold but becomes progressively worse when it gets hot with gear changes becoming stiff and very notchy. An opinion on this would be much appreciated. Thanks.
        
        Gearbox oil synthetic or not?
        
        Posted By : Nigel Gibbins, 17-May-2003, 12:24pm
        
        I have put some seruois abuse throughn my gearbox - as racers do and have had no problems.
        
        My gear change is what I'd describe as quite loose, but I put that down to the remote lever more than anything else.
        
        I haven't noticed any difference between the Syntrax and EP80 (which I used before). I suppose I'll notice the difference when I have to remove the box and can inspect it for wear. And seeing as I;m having to build a new racer now, that will be pretty soon.
        
        NiG
        http://www.niginthecar.net
        
        Gearbox oil synthetic or not?
        
        Posted By : Yan Holland, 18-May-2003, 11:42am
        
        I have just received a brand new recon 'box from Canley and I intend to put Syntrax in, when I finish my current vehicle works (Approx early June) will let you know how the 'box performs through the temperature range; am expecting it to be stiff because selection level bushes are being renewed as far as possible with available parts.
        
        Cheers,
        Yan