Starting Ribcase rebuild

[TulsaFred]

I've got 3 ribcase trans' and a smooth case. Sheesh how do I end up with so many used parts? Anyway, I've been reading the manuals, posts that I've searched, and a nice article from Practical Classics (thanks JPSmit!).

I thought I'd show some pics of the process and get some assistance.

First thing is that I can buy a professionally rebuilt 1275 ribcase from John at Quantum mechanics for $975 with a core. It looks like he replaces the lay gear, layshaft, 1st and 2nd gear, reverse idler, synchros, bearings, gaskets and seals. Parts alone would come close to this, so it seems like quite a deal. No fun for me though! If after inspection it turns out I need most of these parts, I'll definitely bag it and buy the rebuilt unit.

I have a really rough ribcase I acquired for free, so I'm going to start with it and disassemble/reassemble it for practice.

Here it is, partially disassembled:

I have 2 units that look pretty good, and I cleaned the case on one of them. I'll use this ultimately:

 

[TulsaFred]

Re: Starting Ribcase rebuild - first question[s]

1. Why does this trans commonly pop out of 2nd gear? I've read that it is caused by amateur rebuilding according to one pro, but what specifically is the error or wear item that is responsible?

2. What is the purpose of the springs and balls in the synchro hubs? The ones that so commonly fly out across the shop during disassembly/assembly. I'm wondering if these help hold the gear (related to #1 above).

 

[Rut]

Fred,
the springs and balls will give you fits, mine did! I would strongly consider Mike Miller at Comptune for a complete ribcase rebuild...great reputation and much closer! In SC!
Rut

 

[TulsaFred]

I spent quite a bit of time today figuring out the way the transmission works as I disassembled it. I wrote up my thoughts, and will fine tune and modify with input from others with expertise. I'll add some pics too. I find it very useful to understand how things work in order to tinker wisely. I can not vouch for the complete accuracy of this summary, but it's my initial figuring.

How the Ribcase Transmission Works
Fred Willison
Tulsa, OK
March 2015

1. The input shaft goes through a bearing in the front of the case.
   
2. The end of the input shaft inside the gearbox has 4th gear fixed to it. 4th gear meshes with its counterpart on the laygear and turns the laygear.
   
3. The laygear then drives all other gears.
   
4. 2nd, 3rd, and 4th gears on the mainshaft are in constant mesh with their counterpart gears on the laygear. First gear is different – see (10) below.
   
5. The mainshaft inserts into the input shaft. There is a needle bearing on the end of the mainshaft and a hollow, like a pilot bearing, on the end of the input shaft. The two shafts then spin independent of each other. Only 4th gear is fixed to the input shaft, and it turns the laygear.
   
6. On the mainshaft there are two points where power is transferred from the laygear to the mainshaft and thus to the driveshaft. The two points are the 1-2 gear hub and the 3-4 gear hub. These are both splined to the mainshaft. The 3-4 shift fork and the 1-2 shift fork are centered on these points.
   
7. 2nd and 3rd gear spin freely on the mainshaft on bearings.
   
8. The 3-4 gear hub has a slider over it that can move forward (to lock in 4th gear) or back (to lock in 3rd gear). This is done by the shift fork. There are synchros on each side. This is a typical set up for synchronized gears.
   
9. The 1-2 gear hub is different. Moving the 1-2 shift fork forward locks 2nd gear with a synchro just like 3 and 4. Moving the 1-2 shift fork back to catch 1st gear is different. First gear itself moves back, not a slider.
   
10. First gear is splined to the mainshaft, it does not spin freely on a bearing like the other gears. However, it is not in constant mesh with the laygear, so power is not transmitted unless it is forced to mesh.
    
11. To engage first gear, the 1-2 shift fork moves first gear over the splined hub until it meshes with it's counterpart on the laygear. The gear itself moves, not a slider. There is no synchro and the teeth for first gear are straight cut rather than helical, like all the others. Helical gears require a synchro.
    
12. Remember, all gears other than first are in constant mesh with the laygear. Not so with first gear. Power to the mainshaft from the other gears is obtained by a slider (moving over a hub fixed/splined to the mainshaft). The slider grabs dog teeth on the inner radius of the gear, and since the slider is splined to the mainshaft hub, this locks it together with the mainshaft and transfers the power. First gear is splined to the mainshaft and but is not in mesh with the laygear until it is slid back by the shift fork.
    
13. Reverse is an idler gear. It always spins freely. When the reverse fork moves the gear back it meshes in between the laygear and first gear. This extra gear in between the laygear and the mainshaft gear (1st) reverses the rotation of the mainshaft.

Power transfer:


1st Gear:
From input shaft to 4th gear, tolaygear, to first gear, to mainshaft
2nd Gear:
From input shaft to 4th gear, tolaygear, to 2nd gear, to slider/hub, to mainshaft
3rd Gear:
From input shaft to 4th gear, tolaygear, to 3rd gear, to slider/hub, to mainshaft.
4th Gear:
From input shaft to 4th gear, toslider/hub, to mainshaft. *note that 4th gear does turn the laygear, but only to transfer power to other gears via the laygear. 4th gear itelf does not require the laygear to transmit power sinceit is fixed to the input shaft.

 

[smaceng]

One of the things I found out about ribcase gearboxes is that all gears are not the same, even though they may have the right shape and number of teeth. At some point during the run of spridgets, the factory slightly changed the gear hobbing dimensions. Also, just because all the gears fit and may even seemingly work well, it does not mean that they will not whine in 2nd, 3rd and even 4th (BTW: I replaced all the bearings, mainshaft and layshaft). When I built mine, I used a combination of used and new parts....as that was all I could find. The whine was bad, but, I never took it apart to find out why. I have been told by more than one gearbox rebuilder that they can not guarantee that if they rebuild it, the same won't happen. I have been told that some of the "new" gears do not mesh well with the factory gear sets. My advice? Go with Quantum.
Fred, and this does not mean to be disrespectful as I have been in your shoes, but your description above is just the tip of the iceberg of the knowledge needed to rebuild one of these. Good luck!
Scott in CA

 

[Gerard]

fred,

I've rebuilt many of these gearboxes over the last 47 years (I started quite young... :chuncky: ) It's hard to believe you can get a rebuilt one with all those new parts for that little money. He probably can put them together in his sleep and does not have to charge much for labor. Anyway, what's been said already, is correct. There are several different gear sets (you can see a breakdown on one of my Tech pages), which are not interchangeable, and yes, mixing used gear will likely end with a really noisy gearbox. If not done that myself (mixed used gears), but heard many complaints form other who have (witness Scott's comments). I also highly recommend Mike Miller for such a job. He knows the finer points of these gearboxes (as well as everything else Spridget), and is a very helpful guy.

Tech Page: https://gerardsgarage.com/Garage/tech.htm

Look under drop down menu: "Specs/Transmission Parts# Index" You should be able to find a part number engraved or embossed on most of the gearbox parts. Sometimes there are 2 different part numbers for the same gear. Google search on one will usually turn up the alternate number.

 

[nomad]

I rebuilt my BE gearbox with mix and match parts from a couple of boxes. I know its right but people go out of their way to tell me my gearbox need's an overhaul and people give me strange looks when i drive across a parking lot!!

Kurt.

 

[TulsaFred]

Thanks for the input, guys.

Since there were some changes made in the gear sets over the years, I wonder what gears you get when you order from Moss or VB?

Regardless, I think understanding how the gearbox works was really helpful to me, and part of the fun of fiddling with it.

I still don't know the function of the springs and balls in the synchro hubs...??

Fred

 

[Gerard]

I still don't know the function of the springs and balls in the synchro hubs...??

Fred

Fred,

The 3 interlocking balls are what keep the hub selected in any given gear. There is a recess in the mating surface of the our hub that allow the spring pressure on the balls to keep it in place. Otherwise, it would slip out of gear. This is the exact cause of why some gearboxes will pop out of gear, especially on deceleration. Either the detents in the hub get worn or the spring pressure is inadequate. Sometimes other factors like too much end play on the lay gear or other gears can contribute.

 

[TulsaFred]

Thanks Gerard, that's what I thought. Probably a good idea to replace the springs and balls when rebuilding.

 

[Gerard]

Thanks Gerard, that's what I thought. Probably a good idea to replace the springs and balls when rebuilding.

Also inspect the inner surface for any signs of wear.

BTW, I notice your engine looks pretty rusty, especially around the flywheel. It looks like it might have spent some time outdoors. Make sure when you get around to installing the rear seal kit, that you crank flange is in top condition, no surface rust, pits or scratches. It should have a polished appearance like your crank journals.

 

[TulsaFred]

Gerard,
that engine you see in the background is, like the trans I'm practicing on, a freebie. I have it just for parts, it isn't the one I put your nice seal kit on!!
Here's my real engine:

 

[Gerard]

OK, good... so I gathered from your last post... Looks like your doing a fantastic job!

Gerard,
that engine you see in the background is, like the trans I'm practicing on, a freebie. I have it just for parts, it isn't the one I put your nice seal kit on!!
Here's my real engine:

 

[TulsaFred]

And, Gerard, your kit worked perfectly.
I ran the engine on the test stand today, and the leak is completely gone. Dry as a bone!

 

[Gerard]

Excellent! ...

And, Gerard, your kit worked perfectly.
I ran the engine on the test stand today, and the leak is completely gone. Dry as a bone!

 

[pbraun]

Finished this week - now I want another shifter, as mine current one is sort of beat up and rusty.

But, the internals are basically all new!

p.s. Gerard - I put your rear seal kit on the engine before I found a trany problem, and it ran great - no leaks! And a very well built kit it is! Thanks!