cieranc Posted July 16, 2009 Share Posted July 16, 2009 I've noticed my gear changes becoming a bit notchy recently, so today I dropped the gear oil and flushed it through. There was the usual swarf/filings on the plug, as expected, but also the oil was quite black. This oil was changed about this time last year, we had no MTF75 left at the time so I used 75/80 which I reckoned was 'about right' . I flushed it through and refilled with MTF75 today, and the gear changes have improved. On our commercials the oil nearly always comes out the same colour it went in. So what causes the gear oil to go black? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 16, 2009 Share Posted July 16, 2009 Probably because you put the wrong oil in and ran it for a year Quote Link to comment Share on other sites More sharing options...
Ex Member Posted July 16, 2009 Share Posted July 16, 2009 There is a huge difference between 75/80 and MTF94. Not sure what is MTF75? Quote Link to comment Share on other sites More sharing options...
rich90 Posted July 16, 2009 Share Posted July 16, 2009 Probably because you put the wrong oil in and ran it for a year MTF 75W-90 is a highly shear stable, multigrade manual transmission fluid. It is designed for transmissions and transaxles which require an API GL-4, SAE 75W-90 viscosity lubricant, as specified by Ford, G.M.H., Nissan, Toyota, Mazda, Mitsubishi, Daihatsu and others. Quote Link to comment Share on other sites More sharing options...
western Posted July 16, 2009 Share Posted July 16, 2009 Don't forget that inside LT77/77s & R380 main gearboxes is a oil pump, any fluid thicker than the LR spec's will cause problems with lubrication/running of the oil pump. Quote Link to comment Share on other sites More sharing options...
mick110 Posted July 16, 2009 Share Posted July 16, 2009 Don't forget that inside LT77/77s & R380 main gearboxes is a oil pump, any fluid thicker than the LR spec's will cause problems with lubrication/running of the oil pump. these boxes are designed for ATF ...thin as water ....people MUST check mfg. specs.! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 16, 2009 Share Posted July 16, 2009 MTF 75W-90 is a highly shear stable, multigrade manual transmission fluid. It isdesigned for transmissions and transaxles which require an API GL-4, SAE 75W-90 viscosity lubricant, as specified by Ford, G.M.H., Nissan, Toyota, Mazda, Mitsubishi, Daihatsu and others. So EP90 effectively - which is very definitely NOT suitable for R380's. They originally used ATF then moved to MTF94, it's well documented on Ashcrofts site and has been asked on here at least two or three times before. Quote Link to comment Share on other sites More sharing options...
RustyNissanPrairie Posted July 16, 2009 Share Posted July 16, 2009 MTF94 has been fine in my lt77 for 2-3years now. However on a seperate note-I changed the 'box oil awhile ago and found black flakes of material in the drained oil and in the seperate 'box filter extension. turns out the inside casings are sometimes painted and can flake away. Not sure if it was the MTF that caused it-but had no issues sinceand the box is sweet even on cold morning 1st to 2nd changes. Pity the output shaft splines are nearly shot though! Quote Link to comment Share on other sites More sharing options...
cieranc Posted July 19, 2009 Author Share Posted July 19, 2009 My error, refilled with MTF94, not MTF75 . I used Castrol EPX 75w/80 last time, which I understand is the same viscosity as MTF94 (and considerably thinner than 75/90 or EP90 as has been suggested). There is a huge difference between 75/80 and MTF94. Not sure what is MTF75? I was nearly sure they were the same viscosity, anyone know an online source where I can compare specifications? But even with the wrong oil in, why would it come out black? It wasn't paint flakes in it, it came out like used engine oil Quote Link to comment Share on other sites More sharing options...
ajh Posted July 19, 2009 Share Posted July 19, 2009 My error, refilled with MTF94, not MTF75 .I used Castrol EPX 75w/80 last time, which I understand is the same viscosity as MTF94 (and considerably thinner than 75/90 or EP90 as has been suggested). I was nearly sure they were the same viscosity, anyone know an online source where I can compare specifications? But even with the wrong oil in, why would it come out black? It wasn't paint flakes in it, it came out like used engine oil Because you burned it. Do you happen to tow or drive off-road a lot? You might want to consider a temperature probe because most fluids have a hot-point where beyond they degrade significantly. A proper analysis will be able to give you the carbon black content level which will likely be the most telling figure. Quote Link to comment Share on other sites More sharing options...
cieranc Posted July 19, 2009 Author Share Posted July 19, 2009 Yes, our airbag trailer weighs off a shade under 3 tons Quote Link to comment Share on other sites More sharing options...
ajh Posted July 19, 2009 Share Posted July 19, 2009 Yeah, install an oil-cooler on it and you should be fine. I believe Ashcroft sells a kit. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted July 19, 2009 Share Posted July 19, 2009 My error, refilled with MTF94, not MTF75 .I used Castrol EPX 75w/80 last time, which I understand is the same viscosity as MTF94 (and considerably thinner than 75/90 or EP90 as has been suggested). I was nearly sure they were the same viscosity, anyone know an online source where I can compare specifications? But even with the wrong oil in, why would it come out black? It wasn't paint flakes in it, it came out like used engine oil Sorry, I thought you had written 75W90. EPX 75W/80 is the correct viscosity. They do have the problem of using sulfur additives, which can corrode the copper alloys in the synchros. http://www.castrol.com/liveassets/bp_inter...X_Gear_Oils.pdf The Castrol EPX Gear Oils contain sulphur-phosphorus extremepressure additives which enable them to withstand high rubbing speeds and tooth pressures. These additives are activated by high localised temperatures on the gear tooth surface, and chemically react with the metal to form materials (metallic sulphides and phosphides) of low shear strength between the rubbing surfaces. This may be what has caused the discoloration or it may have been overheated. The poor shifting is probably due to it being too slippery at low speeds for the synchros. MTFs have friction modifiers that increase low speed friction. http://members.shaw.ca/jbarge/MTF.htm Quote Link to comment Share on other sites More sharing options...
cieranc Posted July 19, 2009 Author Share Posted July 19, 2009 Well, I'll certainly be using the correct grade oil from now on. Two things to add: 1, the old oil didn't have that distinctive 'burned oil' smell, something I checked for and 2, After a long run, changing down from 4th to 3rd usually results in a grind, if not nursed into gear, even with a double de-clutch (have to let the revs come down to idle then ease it in). This has been the case for the few years I've had it. It seems fine on short towing runs or town driving. Could this be down to worn/damaged syncro rings? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.