gearbox lube - I apologize....

I've lost my nerve. Despite the good results that folks I trust here have had with ATF in the gearbox, and the fact that after totally rebuilding the box and filling it with ATF, this afternoon I am draining it and filling it with 80W90 gear oil.

I'm posting this, instead of just remaining quiet, to preclude any questions down the road (no pun intended) of the "how's the ATF doing" variety.

I'd like to come up with some good technical reason that shows that my decision NOT to use ATF is based on some firm information that it won't work. But since they are spur gears - like the gears in an car's automatic - it seems like the proper use of ATF (coupled with the 80k mile life so far - of a gearbox running ATF as reported here). The sad fact is that I'm draining the ATF and refilling with gear oil is because I'm a chickens#1t.

Because it's thinner and will leak out easier around those silly o-ring "seals' in our gearboxes. Other than that... the scoop on the web say's it's fine.

Might as well go all the way with some Amsoil 75w-140 severe gear.
Worth checking out, here...
http://www.amsoil.com/storefront/svo.aspx

remember if it cost more - it must be better! :shock:

I once was as wimpy a gear filler as you, till I found the ceramic like damage in sleeve bushes that made it too obvious AMC design both flings out lube there and prevents any getting back in while spun up in lower gears. I quized other list's on this and told its ancient practice w/o any down sides to run ATF in AMC's. Then also given other examples of racers siezing triplex primary by using 30 and above oil in there. They found to get lube in chain links needed 20 grade minimum. Also its worth looking up the cross charts comparing engine grade with gear grade. 90 gear is same as 30 engine. So similar to engine oil selection you go mostly by the temps it will be run at and the places it must flow to w/o pressure assist, like cam lobes.

Spend long times at near red line in low gear needed some thin ATF but short shifting normal road use may be fine following manual. Ford type F with friction plate additives would be a bit better ATF for clutch pack than Dextron but I've run both w/o issue. There is a tad less resistance for a tad more response with hot ATF over hot gear lube. Thin oil carries off more heat loads than thicker oil.

BTW even track racers don't spend the time Peel did playing games with sports bikes in tight scary chicanes, miles and miles of em 30-40 min at a time covering over 50-60 miles per game session before collecting to decide next one to try or turning around to do em the other way. No relief on tranny to see much if any use of 4th's 1:1 main on sleeve shaft rest and refilling.

If it costs more it feels better...

RS

mikegray660 said:

remember if it cost more - it must be better! :shock:

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More often than not!

RoadScholar said:

If it costs more it feels better...

RS

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Kinda, but you have to be smart about it.

You may not always get what you pay for but if you buy cheap you will more than likely get crap. For $15 I get 2 gearbox changes (2 years worth) and the peace of mind knowing that my non-wheely, non burnout(a matter of choice), vintage, classic machine has the best protection money can buy. Although there may be better oil that cost more than Amsoil, it's definately in the ballpark.

But that's just me.

RoadScholar said:

If it costs more it feels better...

RS

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i thought we were talking about gear oil - not hookers?


on another note - is there any documentation suggesting new improved syth gear oils are better than something like the old Castrol Hypoy Gear Oil , were not talking about a motor now - i don't ever recall a gearbox failing because of "lesser quality" oil of the right weight - no oil yes..

but to each their own!

Well for now, I'm in the chicken s#1t camp myself about using ATF in the gearbox. Been using Amsoil 80/90 Synthetic lately ... and felt real good about it. But now I'm thinking "are all my bushings in my rebuilt box getting all the lube they need, ALL the time ???" I was apprehensive at even using the Amsoil Synthetic at first, it just seemed to thin, as thin as a 10w even. I didn't see how it could "cushion" the gears enough. But I had read about the "strands" not breaking that gave it it's film strength, and thus it's ability to cushion gears. Seems to me as thin as it is, it would get everwhere ATF would get. HOWEVER, it ATF is really better ??? I want to know what hobot is using ... :?:

Any good gear lube is fine in all condition but rare ones when main and sleeve shafts are under hi sustained load at Hi rpm. ATF is not better than the hi end synthetics, it just plenty good and cheap enough for Peel needs. I've plain jane 90-140 gear lube on hand to use up in plain jane Trixie Combat - I know better than wring her neck out w/o upgrading a bunch of stuff first, but I ain't. But I'd not have a 2nd thought about replacing with ATF if that's all I got on hand at the time. Redish drip hlep trace leaks unless ATF is also in the chain primary too, like i did on Peel till belt tried. I also like ATF in forks over everything else but power steering fluid, which is all I use after trying lots of combos for some years. Could try it both ways use cheap ATF for first break in oil then replace with gear lube and see if ya can detect any thing. I think ATF gave a bit slicker shifts but AMC is already about as good as they get regardless.

Sorry i would not use ATF in primary or gearbox i don't think it has enough lubricating qualities [my experiance don't ask me to prove it].
As the company i work for distributes Maxima motorcycle oils i am running 80/90 gear oil with mtl75 wgt [two stroke gear oil equivalent to 30wgt engine oil]
in the primary and it works for me, yes hobit they do have a 75/90 full synthetic that is suitable for m/c gearbox and diffs but i have not tried it "yet".
Al

Well, since I started this latest thread on ATF I'm now doing my best Brett Favre imitation and saying..."uh, just a second, let me think about this again."

I read for literally hours yesterday re lubes/bearings/bushings and here is the (latest) conclusion I have come to:

(Note that this is rather long and probably of the "who cares, I just use the factory recommended oil" category. I'm not saying I'd argue with that!)

From everything I have read, ATF has plenty of anti-wear properties suitable for the meshing/impact operation of spur gears (like on the commando tranny). It is NOT suitable for hypoid gears but there are none of those in the gearbox. Thinner viscosity oils in general lubricate bearings better because they easily get into all surfaces more easily than thicker oils. They also transfer heat better. ATF has no EP additives that can adversely affect yellow metals (brass/bronze) like the bushings present in the Norton tranny. Though EP additives are needed for helical/bevel/hypoid gears, they are not necessary with spur gears. ATF has less resistance to the gears spinning than gear oil.

OTOH, one must overcome the the natural tendency to ignore the factory recommendations (and logic involved) to put GEAR OIL into a GEARbox. Coupled with this is the history of knowing that gear oil works just fine in the application. Even if ATF might be better, what practical "betterness" does it provide? Based again on all my reading and what I gathered from it, I would say that ATF would theoretically provide longer life for bushings, better lubrication for the bearings and, due to being thinner, less resistance to spinning the gears. But does this translates into any really useful improvement? The only way to tell would be to put two new gearboxes, one with ATF, one with gear oil on a test stand and somehow expose them to the same load cycles and then disassemble them and check everything. At the same time, one could measure if there was any difference in power at the output shaft due to lower spinning resistance.

Further reading indicated that this was the reason that many auto trannies are now using ATF as a fill instead of gear oil and that ATF is a "retro-spec" in many transmissions as well. The key issue is the type of gears being used. In general, if they are spur (straight cut) then ATF is the fill; if they are other than that or a transaxle (ring and pinion) is involved, EP gear oil is used. There is no issue whatsover with ball/roller bearings - they work best with thinner lubricants anyway. Heck, I even read that water is used as a bearing lubricant in many applications and forms the same film between the surfaces that other lubricants do and it cools better and provides longer life than oil. But obviously it can't be used in an environment where rust can form so we won't be filling gearboxes with distilled water!

So I have Farved myself back into definitely leaving the ATF in the tranny.

I think...

I've never felt a need or heard of a good reason to switch from using generic gear lube and I have never had a gearbox failure in any bike, so I'll stick with gear oil, but do tell how the atf works out. I'm guessing there will be no noticeable difference.

MexicoMike said:

In general, if they are spur (straight cut) then ATF is the fill;

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I've rebuilt many car syncro boxes and they all had helical cut gears, ('cept for the old crash first and special straight cut race boxes) and it was these that changed to ATF.
Not that I'm saying ATF won't work in our AMC boxes, it's just wider helical cut gears spread the load better :roll: I would like to see the results of a few high mileage boxes before changing.

Cash

That's interesting. From reading I understood it to be the opposite, that helical gears (or any gears other than spur) impart a "shearing" action between the teeth and that is what requires EP lubricant.

HOWEVER, I may have misunderstood and although I have rebuilt many car trannies - both auto and manual, until the past week or so I never looked into changing the lube from whatever was recommended to something with a different spec. Not sure why I'm doing it now!

almost all the automatic trany's I have rebuilt (35 years in the biz ) have helical gears and most standard also. the T 5 in the 80's mustang's used ATF and also have a paper based braking cone instead if the brass balk ring's with ATF as the lube and gear oil would ruin the cone clutch's. there is some exceptions but very few with strait cut gears. so ATF will work fine in the amc box if you want to use it. I would see NO issue's as far as lube but also as I stated I don't feel it will handle the shock load between the gear teeth if you were to do stuff like power shift's.also as stated it probably would be harder to keep from leaking at places like the kick start shaft O ring

its was hi power hi rpm shifts damage in sleeve-main shaft bushes that made me change to ATF. I broke teeth off 3rd gear chasing back after 900 Duci Monster that I'd slowed way way down to let catch up - for what I define as hi load dumps on AMC cogs. No lube can help the weak teeth so its more the bushes to consider for the lube inside. Next place of wear is the dog flats, then maybe the teeth contacts. I used Ford Type for clutch plated in triplex chain case and Dextron II
in gear box. Its a non issue to use ATF or gear lube - until the going get really hot and tough then ATF is what I put in. Your call of course.