39 or 40 tooth ring gear for a Ruckstell ?

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Model T Ford Forum: Forum 2016: 39 or 40 tooth ring gear for a Ruckstell ?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Sunday, July 10, 2016 - 01:17 am:

Now that Chaffin is making correct 40 tooth ring gears for the Ruckstell we have two options...40 or 39 tooth.

Using a 39 will give you around 2.5% higher gearing.

My question is: do 11 tooth and 10 tooth pinions mesh better with the 39 or the 40 tooth ring gear? Is the difference one to worry about?

Is anyone using a 10 tooth pinion with a Ruckstell 39 tooth ring gear for 3.9:1 gearing?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Layden Butler on Sunday, July 10, 2016 - 12:03 pm:

Wouldn't think you should do that as the 39 ring has a relief on mounting side. The relief would have to be filled.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Sunday, July 10, 2016 - 03:05 pm:

Constantine, The 9, 10 and 11 tooth pinions can only be used with the Standard Ford 40 tooth ring gear. The 12 and 13 tooth pinions can only be used with the Mark Auto 39 tooth and the Ruckstell 40 tooth ring gears. So you have a lot of choices. I believe the 12/40 ratio is the best choice, (3.333) ratio. We make both.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Sunday, July 10, 2016 - 04:48 pm:

Layden, yes, the both the 39 and 40 Ruckstell were not designed to be used in a Ford diff. It can be done though by using shims I believe; that's a different discussion though.

This post is about pinion options and mesh for the Ruckstell.

Glen, so the 9, 10 and 11 tooth pinions cannot be used in a Ruckstell? So what pinion is being used here below on the left under "With Standard Ford Gears"(from the MTFCA "Ruckstell Axle" booklet):




Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Sunday, July 10, 2016 - 04:57 pm:

Constantine, As it says, standard Ford gears 11/40. At the time the book was written we only had 13/39 gear sets for the Ruckstell.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Sunday, July 10, 2016 - 05:09 pm:

Glen, okay so the 11 tooth pinion can be used in a Ruckstell, that's what I thought. It's just that you wrote above: "The 9, 10 and 11 tooth pinions can only be used with the Standard Ford 40 tooth ring gear." A Ruckstell does not take a Standard Ford 40 tooth ring gear.

So can the 9 and 10 tooth also be used in a Ruckstell whether it be 39 or 40 tooth?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Beaumont on Sunday, July 10, 2016 - 08:54 pm:

OK, I am going to throw a ringer in here. On my early 1911 Open Runabout with its original 6 rivet rear end, I am using a 39 tooth ring gear from Glen with an original Ford 11 tooth pinion. Since its such a light car, I wanted a little higher ratio than stock, (and can't use a Ruxtell on a 6 rivet) so a 12 tooth pinion would be too high. The 11-39 combo gives a 3:54 ratio, which works out just perfect. I live in the hills, and it climbs all the steep ones on high, with plenty of power, and goes faster than you'd like on the flats. It took some shimming and fitting to get there, but well worth it in my estimation, it runs smooth and quiet. All this is unnecessary with a Ruxtell, but works well on a fixed axle with a light car. On a Ruxtell, I like the 12-39 or 12-40 combination, depending on weight. Greg Gouveia's 1911 touring ran Route 66 flawlessly with the original Ruxtell 12-40 combination (with 3 passengers & driver.) Best Jeff.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Sunday, July 10, 2016 - 09:15 pm:

Jeff, that's great, thanks for sharing. I guess though you missed what I wrote above "It can be done though by using shims I believe; that's a different discussion though."

Maybe let someone answer my questions first before you take the discussion in the new direction. Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Beaumont on Monday, July 11, 2016 - 01:41 am:

Well Constantine, my point was, in a roundabout way, that an 11 tooth pinion with a 39 tooth ring gear is working great, so that answered 1/2 of your initial question. My understanding of the second half was will a 10 tooth pinion and 39 tooth ring work? Ford designed the 10 tooth pinion to mesh correctly with the 40 tooth ring, as a direct drop-in. Since I have now proven that an 11 tooth pinion will function great with a 39 tooth ring, so therefore will a 10 tooth pinion, (some shimming required) and it would work just same. I also always use Timken bearings in the driveshaft spool, so you can adjust the in/out mesh of the pinion gear more finely. Why you would want to end up with a 3.9-1 gearing on direct in High Ruxtell is beyond me, unless you live atop Mt. Whitney, or in the Gumbo mud of Iowa. Best, Jeff


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Beaumont on Monday, July 11, 2016 - 01:49 am:

One last addendum: I got the ring gear set so long ago from Glen that I'm sure it was made by Mark, and not the new ones he is making now. I still have the matching 13 tooth pinion left over from it. Best, Jeff


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Monday, July 11, 2016 - 11:59 am:

Jeff, Constantine, A Ford 11 tooth pinion does not work with a Ruckstell 39 tooth Ring Gear or a 40 tooth. Sure it will drive the ring gear but you will have way too much clearance. You obviously didn't check the clearance. You had better fix it or you will be stripping teeth off the Ring Gear and loose your brakes. As I said before the 9, 10, and 11 tooth pinions are used with the standard Ford 40 tooth ring gear. The 12 and 13 tooth pinions are larger and only work with the Ruckstell 39 or 40 tooth Ring Gears with the recessed backs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Monday, July 11, 2016 - 12:22 pm:

The more I think about this the more it scares me. Using an 11 tooth pinion with a 39 or 40 tooth Ruckstell ring gear is a very dangerous practice. Yes the gears will fit together but the pinion is too small for the ring gear and you will have a very large clearance. Only the tips of the toes of the gears will make contact and may even tend to skip over each other. If you hit the brakes hard you may break off some of the Ring Gear teeth and have no brakes. Never mix or change gears without checking the clearance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Monday, July 11, 2016 - 02:07 pm:

Jeff, okay; thanks for your input.

Glen, wow...that's a bombshell! I wonder how many people know that? I could be wrong, but I would guess most people with a Ruckstell are using 11 tooth pinions to have "Standard Ford Gears" as the chart above calls it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, July 11, 2016 - 02:15 pm:

Glen is talking about the special Ruckstell 40 tooth ring gear that has a recess on the back side just like all the 39 tooth gears has. If you want to combine a recessed ring gear with a 9,10 or 11 tooth pinion, you'll have to make a shim that's about as thick as the recess, I'd think.
And using any shim between the carrier and the ring gear is a risk and a bad practice as Tom Carnegie has told us. External brakes recommended so there's any brake left when the ring gear bolts breaks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Monday, July 11, 2016 - 02:28 pm:

Roger, you cannot use the shim method for a recessed gear in a Ruckstell can you? Glen is clearly saying, if you have a Ruckstell do not use a 9, 10 or 11 tooth pinion.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Walt Berdan, Bellevue, WA on Monday, July 11, 2016 - 02:33 pm:

Constantine - 9, 10, and 11 tooth pinions are not a match for the special 39 or now 40 tooth ring gears that have the recessed back. Those pinions will work fine with an original style 40 tooth ring gear in a Ruckstell.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Monday, July 11, 2016 - 02:42 pm:

This is maybe why I'm getting confused...I was under the impression that for a Ruckstell you can ONLY use a ring gear with a recessed back; that's not correct? You can use a non-reccessed factory Ford 40 tooth ring gear in a Ruckstell?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Owens on Monday, July 11, 2016 - 02:42 pm:

So is everybody saying that the tooth profile will interchange with all the pinions and ring gears? But it is the backlash that is the problem? Thanks, Scott


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, July 11, 2016 - 02:49 pm:

Constantine, you must differ between the rear axle that is called Ruckstell and the 40 tooth ring gears Ruckstell once produced with recessed back. The geometry between the ring gear fastening area and the pinion bearing area is the same in both standard and Ruckstell axles, so it doesn't matter what type of gear you have as long as it's a pair that matches and fits the Ford geometry, which is the same as the Ruckstell axle geometry.

Ruckstell made recessed gears to make it possible to use larger pinions (12 or 13 tooth) for a higher gear ratio. It's easier to drive with a higher gear ratio with a Ruckstell axle since you have an intermediate gear available.

You can't use standard size pinions (9, 10 or 11 tooth) with a recessed ring gear regardless if it's in a Ruckstell axle or a standard axle (they have the same relative geometry between the gears, remember)
But, if you use a standard 40 tooth ring gear, any 9, 10 or 11 tooth pinion should work. To make the recessed ring gear work you must compensate more or less fully for the recess, that's why I was writing about the thick shim in my previous post. And it's not any good idea.

All clear? :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Constantine on Monday, July 11, 2016 - 03:02 pm:

Thanks Roger, think I've got it now! I was under the false impression ONLY ring gears with a recessed back could be used in a Ruckstell...phew!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Beaumont on Tuesday, July 12, 2016 - 10:47 pm:

I do have proper gear clearance, I thing Glen believes I just bolted in the gears as-is, which would leave massive clearance allowing the the gears to barely mesh, and probably howl like crazy just before detonating. I made a solid shim almost as thick as the gap behind the ring gear and then used the hardened .010 shims to dial it in closer. I then used new grade 8 hardened bolts, and a Timken style adjustable pinion bearing, to get the gear clearance just right. I feel real good about it, time will tell if I am wrong. Best, Jeff


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