Worm Gear Rearend best service information?

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dhetch
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Worm Gear Rearend best service information?

Post by dhetch » May 10th, 2015, 7:21 pm

I have a left hand brake 28AA and a center brake 29AA, both with worm gear rearends. I am looking for the source of the best service / repair information for these rearends. Thanks, Dave

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1crosscut
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Re: Worm Gear Rearend best service information?

Post by 1crosscut » May 10th, 2015, 7:48 pm

Hello Dave, welcome to the forum. There isn't a whole lot of information out there in regards to the worm drive rear end. Here is a link to some pictures I posted a while back showing the insides of a worm drive rear end.
http://forums.aa-fords.com/viewtopic.ph ... ive#p20582
Any specific things you want to know?
------------
Dave

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dhetch
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Re: Worm Gear Rearend best service information?

Post by dhetch » May 11th, 2015, 7:27 am

Dave, thanks for the pictures; they are great. Truth be told, I have been inside each of them 35 to 40 years ago, back when I didn't yet know what I didn't know. Now that I know the value of information, I have a ton of questions like:
How many housing lengths and axle shaft lengths are there and what are the applications of each? What is the specified carrier bearing clearance? Are there differences in hub and drum dimensions when the drums are the same? What parts (if any) are interchangeable from the TT or other sources? Through the years, I have heard many stories about failed brass gears because of the type of lube or the lube not having the right additive; what is the right additive and how much of it do we need?
Thanks,
Dave

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1crosscut
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Re: Worm Gear Rearend best service information?

Post by 1crosscut » May 11th, 2015, 6:31 pm

Well Dave I'm afraid I don't have all the answers to your questions. I hope others will add more information and correct me where I go astray.
As far as carrier bearing clearance I don't believe that there is any way to or the need to set clearances. The ones that I've had apart were pretty straight forward. Just clean them up. Replace bearings as needed. Put in new gaskets and seal em up.
I don't think that the drive shafts and torque tubes are any different between those with emergency brakes and those with only service brakes.
There are differences between the rear ends of the those with emergency brakes and those with only service brakes.
I believe that most all the parts are interchangeable on the rear ends of all the trucks that only had service brakes. (left hand brake) And I believe the same can be said of the rear ends of the trucks with emergency brakes. (center hand brake)

I understand that the bronze ring gear from a TT can be used in the AA rear end. It is a bit narrower than the AA ring gear.

For lubrication just use the 600 wt oil that the vendors sell. The same oil is for the rear ends, dual high, transmission and the steering gear box. No additives necessary.

Where do you hang your hat?
------------
Dave

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tiredtruckrestorer
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Re: Worm Gear Rearend best service information?

Post by tiredtruckrestorer » May 13th, 2015, 7:38 pm

Dave,

The only spec I've found on the worm drives is in the Model T Service Bulletins. In them it said "don't assemble worm drive shaft unless there is from .006 to .015 clearance between washer and bearing".

The Model A Service Bulletins addressed a thrust bearing change and problems with warped or worn rear cover plates. I could look them up if you want more details.

I'd check whose gear oil the Model A dealers are selling and get the specs on it. Dave, you are right. Some of the oils with the EP (extreme pressure) additives can cause problems with yellow metals (brass & bronze). Make sure the gear oils specifically say that they are compatible with the yellow metals. Today you can find their availability more in the industrial line of gear oils than automotive line. I could tell you what I use but I don't want to sound like I'm pushing a certain brand.

Keith

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dhetch
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Re: Worm Gear Rearend best service information?

Post by dhetch » May 13th, 2015, 9:10 pm

tiredtruckrestorer and 1crosscut,
Thanks for your responses. If I recall correctly, the carrier rides on tapered roller bearings and as such, will be destroyed if they have either too much or too little play. So what is just right? I suspect checking the end play will be done before the hubs are installed and involve a person on each end of the axle and one or both ends having dial indicator(s) to check the shaft movement while the other person moves his in. I suspect the readings on both ends should be the same if it is done properly.
The main reason I open the worm gear axle up before I put it on the road is because any trucks I could afford have been sitting out in a farm field long enough that the top of the cab and seat fabric have been gone for many years. These early trucks usually have the dual high and if you check the dipstick for the dual high, it does not seal against the cap that it insert into. When this leaks rain water, the water and moisture in the axle housing severely pits the worm, which will quickly destroy the brass gear.
Keith, my Ford Service Bulletins book recently followed a friend home. If you just give me the month and page number of the section you are referring to, I should have my book back in a couple of days.
Since it is only those of us with worm gear rearends who have to worry about the PROPPER lube for them, I think we need to share what brands will provide written proof that theirs is formulated for brass gears. If yours will provide the documentation, please let me know what it is.
Dave
dhetch

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1crosscut
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Re: Worm Gear Rearend best service information?

Post by 1crosscut » May 14th, 2015, 10:33 am

Dave now that you mention the tapered roller bearing for the carrier it reminded me that the very early worm drive rear ends have a standard straight roller bearing in them. Maybe a carry over from the Model TT? I've only seen the one with the older style bearings.
As far as adjusting the end play I'm not sure how one would go about that if it is even possible.
------------
Dave

KimVanOrder
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Re: Worm Gear Rearend best service information?

Post by KimVanOrder » May 14th, 2015, 5:47 pm

Take your "timken" replacement bearing numbers and ask Timkens service Tech's what the clearance should be. My guess is zero. Just like front spindle bearings. Just my thouhgts...

KVO
KVO
Dec. '28 AA

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tiredtruckrestorer
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Re: Worm Gear Rearend best service information?

Post by tiredtruckrestorer » May 15th, 2015, 8:33 pm

Dave, I use a Lubriplate gear oil number SP0-288 for my worm drives. You can check their website and it will give you the specs on it along with the assurance that it is compatible with yellow metals. What you have to watch when comparing viscosities is what scale they are using. You can check, but the Model A dealers sell a 600W oil which I believe is graded on the ISO ((International Standard Organization) scale. The SPO-288 Lubiplate, on the ISO scale is a 680W. On the SAE scale (Society of Automotive Engineers) it rates high on the 140 grade gear viscosity scale.

You can check Lubriplates website to see if there is a dealer near you. If not, Restoration Supply Company (www.RestorationStuff.com) sells it along with the Penrite Oil line that has similar specialty lubrication products. It also lists what gear oils are compatible with the yellow metals.

Keith

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spectria
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Re: Worm Gear Rearend best service information?

Post by spectria » May 15th, 2015, 9:18 pm

KimVanOrder wrote:Take your "timken" replacement bearing numbers and ask Timkens service Tech's what the clearance should be. My guess is zero. Just like front spindle bearings. Just my thouhgts...

KVO
Kim, most if not all Tapered roller bearings have pre-load to eliminate radial and axial play. Not as critical in a diff as some applications.

https://books.google.com/books?id=yNHul ... &q&f=false
Dave in Quincy, Ca. I love Pics!!!! Post them All!!! :)
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KimVanOrder
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Re: Worm Gear Rearend best service information?

Post by KimVanOrder » May 16th, 2015, 7:13 pm

spectria wrote:
KimVanOrder wrote:Take your "timken" replacement bearing numbers and ask Timkens service Tech's what the clearance should be. My guess is zero. Just like front spindle bearings. Just my thouhgts...

KVO
Kim, most if not all Tapered roller bearings have pre-load to eliminate radial and axial play. Not as critical in a diff as some applications.

https://books.google.com/books?id=yNHul ... &q&f=false

So: Zero clearance to some unknown preload. So how would you adjust this?

KVO
KVO
Dec. '28 AA

KimVanOrder
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Re: Worm Gear Rearend best service information?

Post by KimVanOrder » May 16th, 2015, 8:07 pm

Tappered bearing preload adjustment. (Answering my own question I guess). How not how much.

Since the gears on the axels fit against the spiders on both sides, this would be the max. they can move toward the center. The axel housings are held apart via the matting surface on centerline of vehical. A thicker or thinner gasket will change the dimention between the conical races mounted in the housings. A shim under these races would also change the dimention. Likewise shims behind the tapered roller cages will adjust this dimention. So now we have several ways to adjust the dimention, the gasket is not a prefered method as it is too soft to stack and retain dimentional size. So that leaves us with the shims behind either the race and or the cage.

But the prefered method of how to measure this I don't know. Assemble and try to measure "slop" in axel movement? Then install shims and reassemble? And check again? Still we have the question of how much pre load.

Is there a definitive answer to this?

KVO
KVO
Dec. '28 AA

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