MTFCA Forum

I have a '26 Roadster. Yesterday, while going up a long hill, I tried to shift the Ruckstell into low and it got stuck in neutral. Fortunately, I have Rocky Mountain brakes so I was able to stop rolling backwards and make a controlled stop. And I have a good friend who came quickly and towed me home. I'm getting ready to take the rear axle out of the car and fix it, but I'm not sure what I'm looking for. Ruckstells aren't supposed to have a neutral, so why do I suddenly have only neutral?

What style of shifter does it have on it ?

It has the later style shifter on the axle housing, has a large slot for a screw driver on the forward end.

There are two lock pins that retain the spline plate for low gear. If those lock pins shear off the tips for some reason and the spline plate can rotate in
the housing you will loose Ruckstell low. One pin is also one of the mounting bolts for the shift toggle, the other is a separate bolt with a jam nut on the outside of the Ruckstell housing. Check those bolts as well.

Well that's bad.
Your sun gear may be detached from the system. That would mean your 3 planetary gears are destroyed or gone.
Expect to see major carnage inside the bell.
Then again it could only be a sheared set of ring gear bolts or loose pinion.

The late Stan Howe is here again to address this question.

Have a look at Martynn's great diagrams to see the bits:

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and
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I have had a neutral on my TT Ruckstell when the end of part P122A in the shift lock wore off. Welded up and and re-profiled and we are back in business.

You are at the least looking at a tear down, check and repair of the rear end and the shift lock. It is not as scary as some may think if you get the MTFA Ruckstell book AND FOLLOW the guidance given step for step. (https://mtfca.square.site/product/servi ... se&q=false).

You might get 1 wheel up & see if the shift lock does or doesn't go into the 2 distinct shift positions.
If it does, & you still have all neutral, it may not be a rux problem, but a problem more akin to a non rux problem, like a sheared pinion.
Either way once you get everything disassembled, the failure will be clear.

The first T I got had no Ruckstell but the drive shaft had been welded about 6 inches from the pinion gear. On one of the first tours I drove all the way from Alpine to Escondido for the beginning of the tour and back the same way afterward. I was about 12 miles from home and I thought I was going to need to turn the lights on. Well I was stopped at a light and when it turned green there was a bang and I was in free wheeling. At least I had Rocky mountain brakes. So I pushed it into a nearby parking lot and called our son who took us home. I didn't have a trailer yet so had to borrow one and pulled it home the next day. That short end of the driveshaft makes a good knock off puller for the rear wheels! I screw a nut part way on the axle and the other half to the driveshaft piece.
Norm

I dropped the axle today, dug out my books and videos, and will tear into it on Monday......

ThreePedalTapDancer wrote: ↑

Thu Jul 25, 2024 6:44 pm

The late Stan Howe is here again to address this question.

IMG_3405.jpeg

Stan makes the statement that the bell and the differential carrier is worn here the axle goes thru causing alignment issue and hard shifting.

So I think it was Erik Barrett that posted pix on social media showing him brazing up the place(s) where the axle goes thru and then machining it. I think he even mentioned that often times that area when cooled after the brazing shrinks where most of the brazing is machined out afterwards. I looked in my Ruckstell book for that measurement then (-and just now) and I don't see that bore measurement. Am I missing it??

That dimension is the same as a stock carrier. 1.812" Axle gear: 1.807" = .005" clearance.

speedytinc wrote: ↑

Mon Jul 29, 2024 11:45 am

That dimension is the same as a stock carrier. 1.812" Axle gear: 1.807" = .005" clearance.

OK Makes sense. Thanks!!

I found out the problem, and it wasn't the Ruckstell. The drive shaft failed at the pinion gear key slot. The key, pinion gear, pinion gear nut, and a chunk of the drive shaft and sleeve were all in the bottom of the differential housing. The bearing also has a broken roller now. I rebuilt the rear end about 8 years ago, and the Ruckstell and shift mechanism look good. The ring and pinion gears look good. I'll be replacing the drive shaft, key, pinion gear nut, and pinion bearing.

When I rebuilt it, I had a very hard time pressing the sleeve on the drive shaft. What experience do people have with the adjustable pinion bearing assembly?

Good news on the Ruckstell at least

Hi Randal,
I have used one modern bearing spool, I like the fact that the pinion bearing sleeve part of the drive shaft need not be perfect to install the
bearing assembly. The one that I installed was one that is machined out of a old late spool. It was not bored concentric and not knowing that
every time I assembled it the gear lash changed. Had I known that I could have set up the gear lash by just rotating the spool to get the lash
I wanted.
Craig.

Randal, when assembling the drive shaft assembly to the rear axle, forget about the backlash. Adjust the pinion gear and ring gear mesh to get the correct rolling fit on the gear teeth. The backlash is then what it is, and it may well not be what you might expect.
This is likely contrary to the factory way of setting up the gears, but we do not have the time constraints the production line would have imposed on the axle assembly. "Bung it together. It'l'l work." How many evenly worn original gearsets resulted from this? We can do better.

Allan from down under.

Randy SR wrote: ↑

Mon Jul 29, 2024 10:29 pm

I found out the problem, and it wasn't the Ruckstell. The drive shaft failed at the pinion gear key slot. The key, pinion gear, pinion gear nut, and a chunk of the drive shaft and sleeve were all in the bottom of the differential housing. The bearing also has a broken roller now. I rebuilt the rear end about 8 years ago, and the Ruckstell and shift mechanism look good. The ring and pinion gears look good. I'll be replacing the drive shaft, key, pinion gear nut, and pinion bearing.

When I rebuilt it, I had a very hard time pressing the sleeve on the drive shaft. What experience do people have with the adjustable pinion bearing assembly?

"I had a very hard time pressing the sleeve on the drive shaft."

For the benefit of those playing @ home:

I suspect your failure came about by not getting the sleeve fully seated @ the full depth.
The pinion gear was not making correct contact on the taper allowing the gear to loosen, then shear the key.
You tightened the DS nut but the tighter sleeve didnt move to allow the pinion to fully seat.

To prevent this type of failure:
1) lap the pinion & DS tapers before installing the sleeve. Insure full contact
2) Measure the ID of the inner race & OD of the DS. Hone the inside of the sleeve if necessary for a reasonable press fit. (New sleeves, vendor
manufactured, seem to vary dimensionally.)
The race should press on, but not require brute force. Might be preferred to have a gentle press & add a little green locktite as insurance.
The final torquing of the nut should move the gear & sleeve to snugly butt together.

Thanks for all the replies! Now to find a drive shaft......

Both Lang's & Snyder's show them in their catalogs.

I have had success installing the sleeve by heating in a hot oven and then pressing it on while still hot. have to be very careful to line up the slot for the key which holds on the gear.
Norm