Here are some photos of various ring and pinions. I had this all done once and hit the wrong tab. Had to start over. This is an original Ford set.

Note the position of the bolt holes in the original Ford set. They are positioned so they are in line with the tooth.

Here is a new set from Snyders. These are just recieved but supposed to be old stock from several years ago. Note the position of the keyway and the bolt holes. Note that this set is marked Mark USA.

Here is another set from the same order.

Another set

One more

Wow !!! You -and others- have made a huge expose Stan. This in light of a previous thread highlighting a rash of recent failures of this most important and expensive repopped system. Thanks for taking the effort to post the pictures. Made me go out and inspect my stash of original parts and I can now see that manufacturing knowledge has been somehow lost over the last 70 odd years. Has even our nation's machining skills gone the route of our tennis shoes?

Ford script ten tooth, spline is centered.

One more

Here are a few more shots since I had the camera out. Ruckstell original 3.76. 13/40Here are six gears, four are Ford and two are unmarked.

Stan, all of the sets you bought from Snyder's have the keyway of the pinion in the wrong place. I would send them back. The 3/1 set looks like old stock and should be ok excwpt I see what appears to be 3 chipped teeth in the ring gear. Better check it.

The three to one set is an original Ruckstell set. There are several chipped teeth.

On the script ten tooth I pictured and the script pinions Stan pictured there is an almost perfect dimple or two? Was that Fords way of checking the hardness of the pinion?

For almost 100 years, the ring gears were made with the bolt holes aligned with the teeth, so the ends of the bolts wouldn't hit a pinion gear tooth. One would need to grind a bit off the ends of the bolts to use the new ring gear as it is.

For that same amount of time, all the pinion gears were made with the keyway centered on a valley, so the corners of the keyway would end up under the meat of a tooth. Glen C. pointed this out on the other thread.

It wouldn't be any more difficult to align the components properly when doing the machining, so we must assume that "Mark" didn't know it was important. Let's hope he does now, and that he will take back the new gear sets we all have "in stock" in trade for sets which are manufactured correctly.

Mike.

Aligning the bolt holes with the teeth is a bit more difficult with a 39 tooth ring gear...

rdr

Ricks,It should ba a couple mouse clicks on a cad system today. Don't try to make it harder than it is.

Ricks,It should be a couple mouse clicks on a cad system today. Don't try to make it harder than it is.

Jack, you can align the bolt holes with the teeth in a 39 tooth ring gear only if a separate set of holes is drilled in the differential housing.

David,If you're just replacing one,they should already be there.

David,If you're just replacing one,they should already be there.

Jack, I'm assuming the holes for the ring gear bolts in the differential housing are all in the same location, 10 holes equally spaced, independent of the number of teeth of which ring gear is installed. So with the ring gear bolts located every 36 degrees, and the teeth on a 39 tooth ring gear located every 360/39 = 9.361 degrees, there is no way to align more than one bolt hole with a tooth, one bolt hole will wind up halfway between a tooth on the opposite side.

Perhaps my believeing Ralph was asking about new repro gears is in error. I didn't feel he was just "Stirring it" about bolt holes. But then,I've been wrong before...

I would hope & perhaps even assume that the vendors will check out this information, verify the facts, subject the information to critical analysis(to determine the precise importance of the variation) & then in conjunction with the manufactuer correct the problem. It seems to me that this is exactly what Toyota,Ford, Gm etc do currently. If my reading is correct that is a ptimary way of insuring quality control. I cast no criticism at anyone but given the critical importance of the differantial to the safe operation of the T some prompt attention to this matter is in order. I would expect that most of us who work on our own cars might easily overlook the above discovered variation & in that regard we owe a voice of thanks to those who by training or experience discovered the variation
Ed
Edward R. Levy

Note that the Ruckstell set is actually mismarked. It is marked 3.769. I also labeled the photo 3.769 to see if anybody would pick up on the mistake. The ring gear is 40 teeth, the pinion is 13. If you divide 40 by 13 you actually get 3.0769 or very close to 3 to 1 and the holes for the bolts stay in the correct place, at the bottom of the valley in the gear as opposed to the new sets. Also, notice that the size of the pinion gear remains very close to the size of the standard gear. Interesting. Looks to me like Ruckstell did their homework before they started offering three to one sets. This is actually about 3.1 to 1 but sure makes a nice set. Wish I had a couple NOS ones or that somebody was reproducing a quality set of these gears instead of the 13-39 sets. If I get a chance after supper I'll go out and take some pictures of a new 3-1 set and post those pictures.

Take a look at the new sets, the ones marked Mark USA, which are from Snyders but are probably the same as all of the ones recently available in regards to the hole placement. The hole for the ring gear bolt to come through the ring gear is at the valley of the teeth as opposed to being at the bottom of the tooth, as it is on the original Ford set. If you look at all four of the new gear sets you can see that there is no consistency as to where the holes are drilled in relation to the teeth. While one is directly below the valley, others vary from one side of the tooth to the other. As it appears all of the new gear sets are being made in India, (not the ones shown, the ones that have been causing the concerns) there is probably little incentive for the holes to be drilled according to instructions as they are exempt from any liability for failure. At least that's my idea. I do not have one of the new ones that are causing the concerns, I don't have a NOS Ford set and I have several Ruckstells to get done so I am going to use the sets from Snyders. Since they are marked USA I am going to trust that the pinions will hold even tho the keyways are not where I would prefer them to be. I have spoken to a couple more vendors about this and they seem satisfied that the older sets like the ones shown with the USA mark on them are "probably" OK since they have had no reports of them breaking. I'm spending tomorrow tearing down three more rearends I have in a shed that I had been saving for personal projects, I'm looking for good ring and pinion sets. I don't have much hope for them being useable. By the way, I have fooled with all this stuff and tearing down rearends and calling people and taking pictures and etc for most of a week. Hard to make any money chasing demons.

Yeh, Jack, I was just pointing out that the holes in the wrong place is nothing new to us who have used 39 tooth pinions. You just have to use shorter bolts. Still, it's a sign of unfaithful reproduction. Hmm, there's a word for that...

Yes, Stan I saw your error on 40/39. Does it matter that the pinion on the 40/13 is slightly smaller than the 39/13 pinion? Is it stronger? You still have to break the rearend apart to get the pinion in and out.
rdr

39 Tooth Ring Gear; error compounded..

rdr

Note that it was not MY error. That is what is stamped on the original Ruckstell ring gear. It is in the upper left hand corner of the picture of the ring gear and pinion together.

RD-
When where you at the Tillamook Fair?
I was there Saturday.
-Keith

I was there Friday, Keith, trying to meet up again with Van Beeks, who I had lunch with at the Spruce Goose. Missed them anyhow. Thought about going back Saturday, but Sallie said it wasn't near as much fun as when they went several years ago, when several of the piglets got away. This bunch was real docile. Maybe this is another doping scandal..

rdr