monty Posted August 14, 2014 Report Share Posted August 14, 2014 Confused from Gloucestershire! Time to replace the differential oil but looking @ the original recommendation suggests for example BP 90 EP or say Castrol Hypoy which I thought was non EP. What are people using, an EP 90 or a non EP? My preferences would probably be Castrol, Millers or Penrite. Cheers, Monty. Quote Link to post Share on other sites
RogerH Posted August 14, 2014 Report Share Posted August 14, 2014 Hi Monty, the diff is a hypoid gear system. Unlike gearbox gears they have a certain amount of sliding across the tooth faces going on. 'Extreme Pressure' (EP) oil would be required in order to stay intact. I would have thought the Castrol stuff would have been EP. Roger Quote Link to post Share on other sites
MRG1965 Posted August 14, 2014 Report Share Posted August 14, 2014 Hi flushed both the diff and gearbox with O/D on my TR4 with Halfords EP80w/90 and this seems to work well. I needed 3 bottles for both and have about 1/2 a bottle left for top ups. £8.99 each. Mark Quote Link to post Share on other sites
peejay4A Posted August 14, 2014 Report Share Posted August 14, 2014 I can't remember what Halfords is but it needs to be GL4 in the gearbox. Quote Link to post Share on other sites
MRG1965 Posted August 14, 2014 Report Share Posted August 14, 2014 HI Pete, yes Halfords is GL4. Halfords Gear Oil EP 80W/90 GL-4 1L Mark Quote Link to post Share on other sites
RogerH Posted August 14, 2014 Report Share Posted August 14, 2014 Halfords do both GL4 and GL5 http://www.halfords.com/webapp/wcs/stores/servlet/SearchCmd?srch=Diff+oil&catalogId=10151&action=listrefine&tabNo=1&categoryId=-1&langId=-1&storeId=10001&qcon=fh_location%3d%252F%252Fcatalog_10151%252Fen_GB%252F%2524s%253Ddiff%255Cu0020oil%253Bt%253Ddefault%252Fattr_dd0a556a%253E%257Bav_f66879ca%257D%26fh_refpath%3dfacet_34%26fh_refview%3dsearch%26fh_reffacet%3dattr_dd0a556a%26channel%3ddesktop&initMin=0&initMax=75 Mark - if yours is GL5 then it would be best not to use it in the gearbox. Roger Quote Link to post Share on other sites
monty Posted August 14, 2014 Author Report Share Posted August 14, 2014 Hi Monty, the diff is a hypoid gear system. Unlike gearbox gears they have a certain amount of sliding across the tooth faces going on. 'Extreme Pressure' (EP) oil would be required in order to stay intact. I would have thought the Castrol stuff would have been EP. Roger Yes Roger I have assumed the Castrol Hypoy was an EP to match the other makes in the manual listing. The latest Castrol is either EP80W (a GL4 I think) or EPX80W90 (a GL5). Millers do a GL5 EP90 which will probably be my choice as I use Millers in the engine. I guess a GL5 is a higher spec. than a GL4? Many thanks. Quote Link to post Share on other sites
MRG1965 Posted August 14, 2014 Report Share Posted August 14, 2014 HI Roger, no definitely GL-4. Mark Quote Link to post Share on other sites
monty Posted August 14, 2014 Author Report Share Posted August 14, 2014 HI Roger, no definitely GL-4. Mark Hi Mark, GL4 or GL5 in the diff? (Penrite is GL4 mild EP & Millers is a GL5 EP90). Monty. Quote Link to post Share on other sites
MRG1965 Posted August 14, 2014 Report Share Posted August 14, 2014 (edited) HI, I've used GL-4 in both. After some research I concluded the O/D would be happy with GL-4,which I think is what is behind Rogers thoughts about GL-5 and the diff would be fine too. Mark Edited August 14, 2014 by MRG1965 Quote Link to post Share on other sites
RogerH Posted August 14, 2014 Report Share Posted August 14, 2014 Hi Monty, GL5 is not a higher spec, it is a different spec. There is something in the GL5 (sulphur etc) that attacks the surface of yellow metals. This produces a layer that then can peel off so thinning the parent component. GL4 also attacks the yellow metal but does not peel off. so has a very limited thinning effect. Don't put GL5 in the GB Gearboxes should have gearbox oil in them Roger Quote Link to post Share on other sites
monty Posted August 14, 2014 Author Report Share Posted August 14, 2014 Hi Monty, GL5 is not a higher spec, it is a different spec. There is something in the GL5 (sulphur etc) that attacks the surface of yellow metals. This produces a layer that then can peel off so thinning the parent component. GL4 also attacks the yellow metal but does not peel off. so has a very limited thinning effect. Don't put GL5 in the GB Gearboxes should have gearbox oil in them Roger Yes Roger I have always agreed with you about gearbox oil & use Penrite gear 40 in both cars. My query was for the differential GL4 or GL5? Am assuming the GL4 is adequate.Cheers. Quote Link to post Share on other sites
monty Posted August 14, 2014 Author Report Share Posted August 14, 2014 Hi Monty, GL5 is not a higher spec, it is a different spec. There is something in the GL5 (sulphur etc) that attacks the surface of yellow metals. This produces a layer that then can peel off so thinning the parent component. GL4 also attacks the yellow metal but does not peel off. so has a very limited thinning effect. Don't put GL5 in the GB Gearboxes should have gearbox oil in them Roger Yes Roger I have always agreed with you about gearbox oil & use Penrite gear 40 in both cars. My query was for the differential GL4 or GL5? Am assuming the GL4 is adequate.Cheers. Quote Link to post Share on other sites
RogerH Posted August 14, 2014 Report Share Posted August 14, 2014 Hi Monty, GL4 in the diff should be fine Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted August 14, 2014 Report Share Posted August 14, 2014 Hi Monty, GL5 is not a higher spec, it is a different spec. There is something in the GL5 (sulphur etc) that attacks the surface of yellow metals. This produces a layer that then can peel off so thinning the parent component. GL4 also attacks the yellow metal but does not peel off. so has a very limited thinning effect. Don't put GL5 in the GB Gearboxes should have gearbox oil in them Roger Diffs have phosphor bronze cup washers under the planet gears that are used to adjust the diff gear clearance, most also have the same material thrust washers under the sun gears. Later cars went to fibre/Tufnol thrusts under the sun gears. However....some 'Johnny Come Lately' specialist has reproduced the sun gear thrusts in brass, which seem to fail in no time at all. Cheers Peter W Quote Link to post Share on other sites
ianc Posted August 15, 2014 Report Share Posted August 15, 2014 The 1960s Castron Lubrication Chart says Castrol Hypoy Gear Oil. However, anyone with a limited slip differential needs to use a different type of oil. Ian Cornish Quote Link to post Share on other sites
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