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MG MGB Technical - gearbox and axle oil levels
im going to do a full service on my mgb 1970 model at the weekend i have a manual but it dosent tell me the amount of oil that i need to put in the gearbox it also has no clear instrusions as to where to refill and check the level. i have to idea when it was last serviced engine gearbox or axle. whats the best way of cleaning out all the parts. (i was think of flushing out the box engine and axle with diesel) and any tips on what to expect? |
s truman |
G'day. Gearbox takes 2.5L of engine oil filled (most inconveniently) via the dipstick hole in the transmission tunnel on the RHS just in front of the heater air box. This is where you check the level. It is easier to take the gear shift out and pour oil into the the box from there, but it is a bit of a pain to do that. You can use one of the diff oil type bottles, with the filler tube, filled with engine oil or a funnel with a long hose into the dip stick hole. Rear axle takes 1.3L of diff oil. Again you use one of the bottles with the filler tube. Rule of thumb is put in oil until it dribbles out of the filler hole. I have never flushed a g/box or diff since 1964 when I did it on my first car, a Morris Traveler. After that I lost synch on all gears and the diff was so noisy I had to replace it. The only thing making them work was that the oil was so thick it was like treacle! Cheers Tony |
Tony Oliver |
Haynes Manual says rear axle is 1.5 *pints*. If I recall correctly, I bought 1 litre and it was enough. Gearbox is given as 3 litres (without) or 3.4 litres with overdrive. Handbook: 0.85 litre, 2.84 and 3.4 litres |
Geoff Everitt |
You don't say what manual you have but the Leyland and Haynes manuals certainly contain capacity information, same as Geoff quotes, 0.85 litres for the axle in modern lingo. I wouldn't bother with flushing either, but if you have OD this is usually the time to remove its sump and clean the filter. The filter acts as the gasket between the cover and the casing, so can do what gaskets often do and tear on removal. I opted to buy just one new filter prior to doing two gearboxes, and as luck would have it despite careful removal one did rip and the other didn't. You might like to have a look at http://www.mgb-stuff.org.uk/wn_gearsframe.htm and click on 'oil change', and http://www.mgb-stuff.org.uk/wn_axleframe.htm ditto. Remember the gearbox takes *engine* oil, and the axle takes *differential* oil, not gear oil. |
Paul Hunt |
thanks for all the replies think i have all the imfo to get on with there. can you still by 20/50 oil? |
s truman |
There's Halfords Classic 20/50 http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_166289_langId_-1_categoryId_165581 And Duckhams 20/50 which apparently is no longer green http://www.minifinity.com/distribution/viewtopic.php?t=76203 |
Geoff Everitt |
"Remember the gearbox takes *engine* oil, and the axle takes *differential* oil, not gear oil. " Paul, what weight is the differentail oil you mention vs gear oil which is usually 75W-90W range? I thought regular gear oil (75-90W) was correct? |
R Stegs |
It's the forces it is designed to take that dictates that you need differential or hypoid oil in axles whereas you use 'ordinary' gear oil in some gearboxes like the V8 MGB, whereas engine oil is specified for the 4-cylinder. The viscosities of all three are actually very similar, they are just measured on different scales. For temperatures above -10C Hypoid or EP 90 is recommended for the axle, 80 for temperatures consistently below -10C, and this is the same as for the rack. For the V8 gearbox a lighter oil is recommended, but it can be confusing as the specifications vary from manufacturer to manufacturer. These days the likes of Halfords make things much easier by selling specifiaccly Diffrential oil for the axle, and gear oil for the V8 gearbox. You also don't need to worry about getting specifically 20W/50 for the engine or 4-cylinder gearbox, for temperate climates such as the UK 10W/50 and even 10W/40 are also suitable, and easier to get hold of. I'm a bit chary of Halfords Classic 20W/50 as it comes in unsealed cans so anyone could put anything in it, Valvoline VR1 is an alternative that seems to be available from Classic Mini specialists at least. You do need to be careful with modern engine oils and look at the API rating, as the later SL and SM ratings are not suitable for our engines, causing rapid tappet and cam wear. SJ is the latest you should use, see http://www.mgb-stuff.org.uk/wn_engineframe.htm and click on 'Oils and ZDDP'. |
Paul Hunt |
You can still get Unipart Green Can 20w/50 to API SF rating although it's now in a Grey can. Available from Partco branches, approx �15 fo 5L. Graham |
G Cherry |
Morris oils of Shrewsbury, often a forgotten company, who do excellent oils and an excellent 20w-50. rating SJ. |
Allan Reeling |
well done a full oil service today engine box and diff used halfords classic car oil 20/50 �17 a gallon green in colour. used the same oil in the gearbox to. found the gearbox dip stick behind the centre front speaker, checked the oil level before starting just below the minimum mark drained the oil from the box very black about a litre and a half come out must half been in there for a very long time by the look of it. refilled the box with 3 litres then checked the level only to find it way over the maximum level. so i think about 2 half litres is about right. drained the diff the oil come out of there like a liquid foam! refilled with ep80. thanks for all the imfo thats been posted found it very ussfull. going to be changing door hinges tomorrow wish me luck lol |
s truman |
What all of us failed to mention is that the capacities quoted were for *dry* gearbox and axle, you can never get all the oil out when draining, so less than the stated capacity is required for the refill in an oil change. |
Paul Hunt |
This thread was discussed between 29/07/2009 and 02/08/2009
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