Gearbox synchroniser hubs

[miked]

I have a question. The more times I open a gearbox I learn something or question things.
On, say the 3rd/4th synchroniser hub, you find the inner profile on the outer hub (sleeve in usa, i believe) worn were the keystone dog teeth sit/engage. I have a spares/scrap box with 1/2 a dozen of these and the wear is interesting. Most are just worn on one on side and the other sides are parallel. Were as one hub outer has dog teeth witness marks on both 3rd and 4th sides.
Am I right in saying that these inner teeth of the outer hub (sleeve) start off perfectly parallel and subsequently take on the wear marks of the keystone gear dog teeth. Or, as i first thought, the hub/sleeve have opposing dog teeth to lock the two components together.
Is it constant changing down to 3rd from 4th that has the hardest life?
Whilst i have fitted new hubs many times i have never really taken time to look at the new inner teeth.
Cheers Mike

[2cams70]

Interesting - do you have pictures to further explain what you mean?

[Craven]

This is a pic of a NOS Ford hub, I posted some time ago when blocker bar types being discussed.

[2cams70]

"Keystone dog teeth" - ??

[miked]

Thanks guys. Will post when i get back home,
Photo looks parallel.
By keystone i refer to the shape of the dog engagement teeth on the gear. They are shaped like a cuckoo clock. Pointed roof and sides tapering inwards as they go down towards the actual gear teeth.
Not referring to anything to do with dog gear type boxes.

[miked]

A 3rd gear showing dog teeth and shape.

[attachment=0]ECA1075C-9F2D-4B8A-8D2D-BFDC2D54285C.jpeg[/attachment

[miked]

Synchroniser outer sleeve/hub

You can see one side of this is parallel, whereas the other side is worn to the shape of the gear teeth.

[miked]

My conculsion is that new synchroniser sleeves are parallel as per the photo by Craven. I also checked with a gearbox parts supplier. He confirmed. Since the dog teeth are shaped they cause the wear pattern shown. My overaul concern was preventing using worn parts that cause dropping out of gear on the overrun or under load. I have used new synchroniser hubs since I had a box with a brand new shafts and gearset start to come out of second gear under load. I had used what I thought to be a good hub. This was on a straight cut box and i could actually feel the stick pushing it way out under acceleration. I believe straight cut would also be the box with least amount of later pressure. The selector forks were mint so the gear was engaging fully. No clearance issues with body or gear stick. All checked.
I understand that the detent springs and balls assist in engagement to s small degree but lateral force must drive the dog teeth out of the hub sleeve when wear is evident on the sleeve teeth.
Or have i got this wrong? Would be nice to hear from somebody more knowledgeable to make a more informed decision about worn hubs. Or does everybody just buy new hubs. Found this link which shows dog teeth, sych ring and hub. Shows both shaped.
https://images.app.goo.gl/tLdRrNgZT3JiCR886
Mike

[2cams70]

I've never had issues with jumping out of gear with the standard ford gears even with old worn syncro. hubs. A possibility is that the rake angle on the sides of the engagement dog teeth on the replacement straight cut gears is incorrect and therefore imparting a lateral force on the syncro-hub under load.

It wouldn't surprise me too if straight cut gears are more critical in that area than helical. That whining sound you hear with straight cut gears is the result of a vibration created by the meshing gears and transmitted through the whole gearbox.

[miked]

Fair point on that S/C box but i had a box in a Plus 2 that kept coming out of 3rd. Cured it with new hub. Standard Helical. I have a mates box with 3rd gear dropping out. As you say i have seen boxes with really worn hubs that stay in.
I tend to shim the detent springs but i think that is very marginal in helping.

[miked]

Still not happy with this. Al you must have a view. Would appreciate your opinion.
Just bought a new 3rd 4th synchro outer sleeve that is parallel one side on the teeth but has formed teeth on the other side that are like the mirror image shape of the gear dog teeth. It is a later hub sleeve
On 4 of the 8 old sleeves that I have there is is a driil mark on the side that always has the formed teeth. Not the parallel side. This must indicate a fitting direction.
Just to throw things further, i have another good gear set (damaged lay cluster) that has perfectly parallel teeth right through on both 3rd/4th hub and 1st/2nd hub. This proves then that there are different hub sleeves made.
I can't get hold of thr supplier of the new hub as he is on holiday. That new hub does not have a drill mark but a line turned in the same side as the others, on the formed teeth side. Thus indication a fitting direction.
So, which side goes to 4th gear, the marked side with the drilling and the formed teeth or the parallel side. I realise this is a bit anorak but it is bugging me. Also can't rely on taking a box a part and everything being as it should be with the age of these now.
Cheers Mike

[nmauduit]

Still not happy with this. Al you must have a view. Would appreciate your opinion.
Just bought a new 3rd 4th synchro outer sleeve that is parallel one side on the teeth but has formed teeth on the other side that are like the mirror image shape of the gear dog teeth. It is a later hub sleeve
On 4 of the 8 old sleeves that I have there is is a driil mark on the side that always has the formed teeth. Not the parallel side. This must indicate a fitting direction.
Just to throw things further, i have another good gear set (damaged lay cluster) that has perfectly parallel teeth right through on both 3rd/4th hub and 1st/2nd hub. This proves then that there are different hub sleeves made.
I can't get hold of thr supplier of the new hub as he is on holiday. That new hub does not have a drill mark but a line turned in the same side as the others, on the formed teeth side. Thus indication a fitting direction.
So, which side goes to 4th gear, the marked side with the drilling and the formed teeth or the parallel side. I realise this is a bit anorak but it is bugging me. Also can't rely on taking a box a part and everything being as it should be with the age of these now.
Cheers Mike

worn synchro

Hopefully not confusing matters as I'm not 100% sure I got your issue (which part is new vs. which one is thought of causing trouble), but I would think that on your photo edited above the wear pattern is the same for both gears, only the red side is much more pronounced than the blue side.

[2cams70]

Sorry but really hard to know what the issue is without more pictures

[miked]

Thanks guys,
I have a few outer sleeves and they all exibit more wear on one side. It is the side i mentioned that has the drill mark. Please see first photo. Note drill mark on side of sleeve. I no longer have the offending dropping out of gear but have numerous outer sleeves that exhibit hardly anything on one side and lots on the drill mark side.
Having trouble with file sizes. Will post somemore in a minute.

[Craven]

Last pic shown by ?nmauduit? is for the early type, with these they were always in pairs inner and outer. These are coded for relative position by an etched line on both parts, if you have the originals this marking will tell you the direction of fitment.