gearbox oil

[Wookey]

The manual says SAE 75W/80W. I have a load of EP80. I guess that's not a suitable substitute? I've just done some searching to try and understand the numbers, but not found much enlightenment '75W/80W' is a tricky search. Engine multigrade oils Have one W for the min temp. So what do two W numbers mean? Still a multigrade oil presuably. And why doesn't it say 'EP'? Shouldn't it - being a gearbox+diff?

(Expert 1.9 (NA) D gearbox, now attached to 1.9TD engine). I never managed to work out which number that is.

[myglaren]

You appear to have acquired a spurious "W" somewhere along the line

[citronut]

the 75 and 80 are viscosity's ,

i dont know why they put 75 and 80 on the same can???

maybe they should call it 77.5W

[Wookey]

RIght, that makes more sense. So my handbook saying 'Esso gear oil BV 75W-80W new formula', or 'Total transmission BV 75W-80W new formula' is just hopelessly confused. I see that there is no such thing as 75W-80W to purchase, only 75W-80. My Russek manual has copied the error from the handbook presumably, as that specifies SAE 75W-80W too (in two places, so it's not a typo).

What about the 'will EP80 do instead' point? Presumably EP80 is the same as the 80 in 75W-80, so it'd be fine in summer, but maybe a bit too thick in winter? Ah yes - here's a useful page: http://www.bobistheoilguy.com/putting-t ... viscosity/" onclick="window.open(this.href);return false;
Looking at the datasheets we find that Total BV 75W-80 is 49 mm2/s at40C, and 8 mm2/s at 100C. Smith Allen EP80 is 76 and 9.4 respectively. A different oil from total "TI 75W-80" is 64 and 9.5, so that seems like it wouldn't be an unreasonable substitute, especialy on an older box where a bit of extra thickness may not be a bad thing.

[citronut]

seeing/hearing the problems/damage caused to the PSA gear box when the wrong oil is applied,
i would stick to an oil specifically ratted for these box's, what ever the brand

[Peter.N.]

EP oil used to be used in steering boxes and some rear axles, I think it stands for 'Extreme pressure' the grade for steering was 140 - very thick.

Peter

[Wookey]

EP is indeed 'extreme pressure' which particularly occurs in diffs. The 'EP'ness is graded in GL1-5. The standard SAE 75W/80 is GL4 'OIls for various conditions'. EP80 is GL5 'oils for severe conditions', which is better (higher percentage of EP additives). The merits or otherwise of GL-4 vs GL-5 lubes in syncro gearboxes seems to be a little involved/controversial. There is some good (old) info here: http://www.widman.biz/uploads/Transaxle_oil.pdf" onclick="window.open(this.href);return false;, and some more recent info here: http://www.bobistheoilguy.com/forums/ub ... 144&page=1" onclick="window.open(this.href);return false; and a good 2004 discussion here: http://www.bobistheoilguy.com/forums/ub ... 267&page=1" onclick="window.open(this.href);return false;

The bottom line seems to be that you can use a GL5 oil in a gearbox, so long as that gearbox does not have brass synchonisers, or the oil is 'modern' and has the right sort of additives. Does the BE3 have brass syncronisers? In the US it's hard to buy GL-4-only oil, but we still have several suppliers over here.

This turns out to be an interesting subject (if you are a geek , and that bobistheoilman site seems to have the best info.

After way too much reading I've concluded that I could just put EP80 in and it would probably be fine, but it'd be thicker then ideal on cold days, it may not have the right friction modifiers for nice synchro gear changes, and if there are brass bits in there it may well double the wear rate. (also the tub I have is probably 20 years old and thus may predate more brass-freindly compositions and also may have acidified in that time). So it would have been an interesting experiment, but in the interests of not giving myself unnecessary work I'll go and buy some of the right oil tomorrow

[RichardW]

The BE3 doesn't like heavier oils - the gearchange gets very stiff at low temps. The two figures on multi grade oils refer to "It won't get thicker than x in the winter" (the first bit) and "Won't get thinner than y when it's hot" the second bit - so 75W80 is no thinner than 75 grade straight oil and no thinner than 80 grade straight oil. EP80 might be OK, but the change might be stiff when cold