MTFCA Forum

Last Sunday I drove my ‘15 touring to the hardware store, about a 10-mile round trip. Coming up a hill in Ruckstell low, Ford high about 50 feet from my driveway there was a loud bang and a sharp jolt, then the back wheels locked up, the engine died and the car skidded to a stop, leaving two skid marks. It all happened very quickly. Being stopped in the middle of the street, I pulled the brake handle vertical and tried to roll the car backwards to the curb. It rolled a couple of feet and the back wheels locked again. I was unable to shift the Ruckstell out of low. Being close to home, I hooked up a tow strap to my truck with a friend driving it, with the intent of dragging the T with locked rear wheels to my garage. Once the car was moving, I was able to shift out of Ruckstell low, at which point the back wheels started turning and the car got up the driveway and it was easy to hand push into the garage. Jacking up one rear wheel and turning the driveline with the front crank, I found the issue was related to Ruckstell low. I disassembled the rear end today, and confirmed my suspicions. The planetary gears, in rocketry terms, “experienced an up-planed rapid disassembly “.

Some history. I have owned this car for 23 years; I didn’t get much past history with it when I purchased it, and it needed some work. It had the Ruckstell when I got it. Based on the Ruckstell’s serial number and brass shift tower, it is a very early model. The car spent about 15 of those years under cover when I didn’t have time for the hobby. With retirement and Covid, I found the time in 2021 and for a year worked on the restoration, getting the car back on the road in 2022. Part of the restoration was going through the rear axle; I got the book and learned along the way. The babbit washer had been replaced, but I put in a new one anyway. I also replaced the outer Hyatt bearings, races and axle seals, the axle spacer washers in the differential and installed a Fun Projects pinion bearing. Everything else looked OK, the axle housings appeared to be straight, clearances, axial adjustment and ring/pinion engagement all looked good. The car came with high speed 3:1 ring and pinion, and after driving the car for a while I decided that living in hill country with a heavier touring I needed to go back to stock gearing. So 18 months ago I opened the rear axle again to replace the gearing. I also decided to replace the axles and differential gears (thanks to a very generous forum member who gave me a couple of hard-to-find gears). Everything else still looked good, and the car has run and shifted flawlessly for about 300 miles until last Sunday’s episode.

Now to round up some parts.

I’d like to ask the more experienced members here if this is something common, and what might have caused this failure?

-Mark

It may just be as simple as one planetary gear tooth breaking off and causing havoc from there. It would be nice to know, but that won't effect the outcome and the rebuild required.

Allan from down under.

I would look into the pins and gears. It almost looks like the pins are discolered from heat. The gears one the pins may have seized on the pins and then bang.

Chad,I have seen that happen before. One gear actually got so hot on the pin that it "welded" the pin in the carrier before it seized and sheared the pin off. The absolute mystery was this happened in a high mileage car, driven daily, but did not happen until 3 years after a complete rebuild.

Allan from down under.

Keep in mind, you are either in Ruckstell or you are not! Ruckstell low would be low pedal and Ruckstell.

Perhaps you were getting low on lubricant? I haven't heard of that happening to a Ruckstell. They are almost indistructical.

Thanks the replies.

Although the pins show some radial discoloration, they are smooth, straight and measure within tolerance. I didn't find any evidence of seizing either on the pins or inside the bores of the planetary gears (what was left of them!).

There was sufficient oil. I had checked it about 30 miles before the failure, and the rear axle is one place I have no leaks. The oil that came out looked pretty clean.

Regarding how I mis-worded high and low gearing; fair point. I should have said Ruckstell was engaged, in high pedal. This equates to 3rd gear in my car. I generally am able to go up that particular hill in this gear with myself and one other person. If more people than that, I need to dis-engage Ruckstell and use low pedal (second gear to me).

I have found that the holes in the cast housing that hold the planetary gear pins are somewhat egg-shaped. This is something to look for according to the book, but apparently I failed to zero in on this the last time I had the axle apart. I suspect that this caused the gears to move out of alignment, eventually causing a tooth to break. As Allan pointed out, once one tooth breaks off, all of the other gears in that small gearbox quickly join the party.

I am still learning, and have been reminded that some lessons cost more time and money than others!

Thanks again for the insight.

-Mark

Mark, if the p160, the main cast piece the holds the gear pins, is broken, start looking for a new or rebuild-able one. I need one since mine has the holes badly wallowed out. Chaffins makes them but are on back order waiting on their machine shop to finish up new castings. Maybe other vendors have it in stock. It comes as a kit, P202, which also includes the P141 cover and the bolts and nuts.

jsaylor wrote: ↑

Thu Sep 19, 2024 4:43 pm

Mark, if the p160, the main cast piece the holds the gear pins, is broken, start looking for a new or rebuild-able one. I need one since mine has the holes badly wallowed out. Chaffins makes them but are on back order waiting on their machine shop to finish up new castings. Maybe other vendors have it in stock. It comes as a kit, P202, which also includes the P141 cover and the bolts and nuts.

Wallered castle holes can be bushed. Slightly worn holes are not a problem, however when apart, I vote for a complete repair or replace.
Slight wear doesnt effect function as long as the pins are still fitting well in the upper plate. There should be NO heat discoloration on the pins.
Those pines are about .005" under the gear holes of .500. They need the clearance. Big mistake to replace those pins(to tighten the slop) with .500 pins. The gears should have 2 holes that "pump" the gear grease into the pins. Even a broken pin tower doesnt normally destroy stuff. It usually floats in position. The heat source/reason is what causes these catastrophic failures. Loosing a tooth off a planetary rear is not a common situation.
Because of the difficulty of lube getting into this differential area, by design, its best to gear your T so that Rux isnt the primary drive ratio.

Thanks for the heads up on the availability of the P-202 differential housing. I spoke to Dave at Chaffin’s today; he was very helpful, as always. He said they are trying to expedite a small batch of housings from their machine shop, and would have more definitive information tomorrow.