WANTED: Worm drive pinion gear set

[popcorn-guy]

I am looking for a NOS 5.17 worm drive pinion and gear set for a 28/29 AA differential. Contact via this forum or at 707-824-2882. Thank you.

[Neil Wilson]

Hello Alan,
FYI - for the worm drive axle with 5.17 gears, there is an AA-4610-B worm and an AA-4210 worm gear. Ford does not list these parts as a pinion and gear set. As long as you get what you need, the part names don't matter!

[popcorn-guy]

So there will be a clarification of old terminology (technical term) and todays vernacular the following. This should provide the assistance for any one that may have been confused about either.

Ford Part List Worm Driving Gear = Today Pinion Gear

Ford Part List Worm Driven Gear = Today Ring Gear

I hope that this will assist any that may have been confused. My appologies for the possible confusion.

[REM]

I think the interesting thing here is that in the worm drive axles the two gears are not furnished as a matched set as in the ring and pinion sets we are more familiar with today. It seems it would be ok to change one and not the other if both gears being used were in good condition.
Is this correct thinking?

Richard

[popcorn-guy]

Well Richard, from my perspective it would seem logical that the "worm driving gear" aka pinion, would be the most likely canidate for replacement as it is of the softer material by far and I would think that the "worm driven gear" aka ring gear would not hardly experience wear, if any. There may be other issues within the case that could be experienced that would cause one to be required to replace both. As I have not had any reason to open up my worm gear diff. I'm unable to provide a pat answer, if there are any, on that one. I will check with a fellow in KS who has been dealing with AA trucks for 40+ years and has always opened up the worm and bevel diffs to refurbish them prior to them going back on the vehicle. He most likely may have an answer to this question. Another factor today are the additives that assist the lube to stay with the substrate better. That may be minor, but it's there.

As these worm diff's are heat sensitive, I would like to ascertain if the modern synthetic lubes would be of assistance? As they seem to have better lubricity I would think that it would reduce the heat on the "worm driving gear" thus protecting its' longevity. I don't think I would test my luck on attempting to run it at real high speeds because of that, as there is always the diminishing return factor.

[Neil Wilson]

Alan,
The worm is made of steel and is usually not worn. The worm gear is made of bronze and is the gear which wares out.

Someone sent me information on a modern day worm gear lub that was to reduce head. Hopefully, that person will see this discussion and respond.

[popcorn-guy]

My apologies for the error on which was made of which. I was acting on errant information from an individual who had "peeked" into his worm diff. and related that the worm was bronze. He may have inadvertently switched the terminology unknowingly and as I have not personally had the need to work on one, subsequently was unaware of the combination. Regardless of which is which, the bronze will wear out prior to the steel as indicated previously.

I to would find it useful if the individual who knows of a lube for these diff. was to see this and add to the subject. When I get a moment I will attempt to get off an e-mail to Amsoil and RedLine to see what they may have to offer in information and recommendation. They seem to be the two front runners in synthetic lubes.

[E.Moore]

Synthetic gear oil is far superior to petrolieum based gear lubricants, particularly for anti shear properties; however, synthetic lubricants will find the smallest places to leak from. As the rear axle housing heats up from driving & braking, synthetic lubricants will leak past the Model A/AA rear axle seals and will eventually get all over the rear brakes. The rear axle housing will also leak at the housing gasket and the oil plug.

The Model A/AA axle housings are not vented like modern vehicles, so as the heat increases in the housing, the air pressure inside the housing rises and the more likely it is to cause a lighter viscosity lubricant to leak past the seals, especially when we are using old axles with wear grooves from old seals.

One reason Ford used the heavy 600 weight gear oil was to prevent gear oil loss. Ford engineers knew from Model T experience that the seals would not completely keep lighter viscosity gear oil contained into the axle housing. On disassembling a Model T/ A / AA rear axle, the rear brakes are often covered with rear axle gear oil/grease/sludge, due to either a seal problem, or from use of a lighter viscosity gear lube, or a combination of both.

Since 600 weight oil is no longer available, a combination of modern gear lubricants is often used to get closer to the 600w viscosity. I recommend using petrolieum based lubricants to minimize leakage problems.

I am not a final expert on this issue, but with more than 35 years in the automotive service industry and as a factory field service rep with a major automobile manufacturer, I have experience with both synthetic & petrolieum based lubricants.

[popcorn-guy]

Hello Mike,
Is there any reason not to vent the axles? If, while the axle is apart for refurbishing, one could install a vent without the concern of having shavings fall to the interior and not being able to clean up.

Would this elevate the pressure problem of oil/grease migrating, either mineral or synthetic? Or are there other issues involved?

[rsierk]

First of all, we should not refer to 600W as "600 weight". That is not what the W means. 2ndly, it is a product owned by Mobil and still produced today, although I have heard some say you must buy at least 5 gallons. Some of the A parts dealers buy it and repackage to smaller containers. Some are selling 85W140 and calling it 600W, so watch out if you really want the genuine stuff. This is not to say that it is better than more modern lubes. Some synthetics, by our (my employer) laboratory testing, have the ability to extend the life of gears and lower temperatures at the same time (higher speed boxes than AA rear ends).

[Neil Wilson]

So, what does the "W" mean? And, what are your thoughts regarding the prior conversation on synthetics resulting in leaks around seals. And, what are the names (identifyers) of the synthetics you refer to?

[rsierk]

As I understand it, 600W is a trade name owned by Mobil, registered back in the 20's. The product is now Mobil 636. As far as synthetics go, perhaps the testimonial from Fordbarn is more pertinent to A or AA differentials than our company's test results, which showed some synthetics more effective than others (Mobil was good): http://www.fordbarn.com/aforum/messages2/308182.html

[E.Moore]

After reading all the conflicting perceptions on the meaning of "W" for lubricants, I was able to find the meaning from Mobil.com...The current 600W is still used in steam cylinder applications because when it is injected into a steam cylinder, it will coat and protect the metal parts against corrosion. The 600W steam cylinder oil is not the same as the old 600W gear oil used by Ford. Mobil does own the "600W" name, but 600W is also available in Mobilgear 600 Series and 7 varieties of 600 series lubricants are available, depending on viscosity. Mobil engineers also state that the letter designation "W" refers to Viscosity which is often referred to as "weight", because the various weight (viscous) oils are determined by means of the ability to pour at cold temperatures. Mobil's website explains " Straight weight" refers to an oil's viscosity, and usually indicates an absence of viscosity index improvers." So the letter "W" can be used as "Weight".

[popcorn-guy]

Thank you Mr. Moore. While talking to Lubrication Engineers about their "worm drive" lubricants I also asked him about the 600W issue and he said that if one continued to read the label it would say "steam cylinder oil". It was originally a mineral oil, according to him, but now has been synthesized for the most part. I was surprised to find out that "regular mineral oils" are still spec'd by gear manufactures and automotive companies for certain applications. This subject could go on for months with all that one could learn about it.

If one is interested in Lubrication Engineers worm drive lubes, as well as for bevel gears, go to: http://www.le-inc.com/index.jsp . Call them as they will be glad to discuss your interest in their products. They are very cordial.

If you call Marty at: http://www.speedwaymotors.com/default.aspx he can tell you about the LE lube oils that he uses in his QuickChange diff. which uses essentially a banjo case with the ability to have spur gears to change ratios. Most of us are aware of these. He talks about the "tackyness" of LE's oils and how it has all but eliminated his diff. gear problems with his Silver Crown cars. He relates it to our grandmothers beating eggs with the mix master and the eggs climbing up the beaters at they revolved. It's best to talk to him to obtain the information as there is quite a bit and I would not want to attempt to repeat it without error.

I will be using the LE products in the future as they are mineral based and also venting my axles after talking to the engineer at LE. By venting, one allows the gear case enclosure to maintain a constant pressure. As we know the air heats up from the gears being used and then as it cools causes the air to be drawn in through the seals as it condenses. By venting, that maintains a constant pressure and assists in keeping contaminats from being drawn in. Running a vent hose up higher than the axle, as high as practical and putting a small air filter on it, one will almost totally eliminate dust and dirt from being drawn into the gear case. He advised that the problem arises from the air distrubance from the oil pan which creates a swirling action kicking up the dust and dirt. Subsequently the vent hose needs to be up out of the air stream.