MTFCA Forum

Within the next few months, the standard T rear axle assembly under my 27 coupe, will be swapped out for a Ruckstell, The Ruckstell axle was bought from a club member and Forum user who told me he had it rebuilt to go under a speedster project, that didn't materialize. He claimed it had a 3 to 1 ratio, ring and pinion (13-39) and was ready to install. Not taking any chances, I am having it disassembled and checked out by an experienced Ruckstell guy.
I have read many times on this Forum and other places that a 3 to 1 ratio axle, requires a very strong motor, especially in a heavy 26-27 enclosed car, and that a 12 tooth pinion, producing a 3.25 to 1 ratio is a much better choice. My 27 has as strong a motor as can be had, without going the OHV route. It has a Scat crank, a Stipe 290 cam, a Prus head, Model A intake and exhaust using either a Model B Zenith or a Stromberg M-1 carb.
Taking this into consideration, I am seeking advice from member/owners who have had, and used, either a 3 to 1, or a 3.25 to 1 ratio Ruckstell, as to whether I should change the 13 tooth pinion to the 12 tooth.
I live in Northeast San Antonio, Texas, on the southern edge of the Texas "hill country". There are some pretty good grades around, but certainly, nothing like you'd find in far west Texas, or other states with 'true' mountains. Since the Ruckstell has a geared down "low" range, is it worth changing the 13 tooth to a 12 tooth pinion. I guess a case could be made that by changing to a 3.25 ratio, it would help the motor by producing less "stain' on the motor. I welcome comments from those with 3 to 1 or 3.25 to 1 axle experience.

Sounds like you have enough motor to pull 3-1 gears in your coupe. Do you handle the hills now with stock gears? That would be my decider.
3-1 in rux is still a bit lower than stock 3.66. My preferred ratio is 13-40 (3.07) I have these in 2 T's. Touring & roadster P.U. Both have strong motors like yours - equivalent. I have driven both up to the mountains 2 persons & full camping gear, 8k feet. No problem. Speed limit 35. I can easily maintain a comfortable 35 all the way up in rux.

I have 3.25's in my 14 roadster. That gives me plenty of top end to get there, but a slower option when club touring. As a group we tour slow.
I take the rear & speed to play catch up from missed lights. Most hills I take in direct if not caught behind slower cars.
If you are not happy with your current local hill performance, then 3.25 would be good/preferred.

Let me warn you that changing to the 12t pinion gear requires a big shim to bring the ring gear up for proper mesh. Shim/shims greatly increase the possibility of shearing the ring gear bolts. I made one shim (about .090") out of T6 aluminum. So far so good.
If it fails or if I build another 12T rux, I will look into machining the rux bell down that .090" & using a stock ford 40t ring gear.
Hopefully your rux guy is familiar with a 12t conversion.

I have 3.25 gears in my 26 coupe. It’s a good all around gear but I usually take off in low ruckstell just to be a little nicer to the low band.

Andy

I took my Ruckstell with 3:1 gearing out of my lightweight speedster before i sold it to a novice T driver because the 3:1 ration seriously compromises the Ford transmission braking ability. You really do need accessory brakes to run a 3:1 diff.
When I put that Ruckstell into my wide body roadster I fitted a 12 tooth pinion to get the 3.25:1 ratio rear end. Rather than fit a shim behind the ring gear, I set up the diff centre with a custom made set of bronze washer and steel spacers. As John says, shims are not the ideal solution.

Allan from down under.

Do yourself a favor and ditch the 3:1 gears in your coupe. Go with the standard gear ratio. Better overall performance. The reality is you will appreciate the take off and torque benefits much more than the eventual increase in speed. 45-50 mph with a good motor is plenty.

I agree with Mark. I don’t like 3:1 gears even in a speedster. Except for cruising it never seems to be the right gear. I do a lot of club tours and with the 3:1 you don’t want to get behind a poor running stocker going up a hill in low ruckstell listening to each coil buzz.

Andy

AndyClary wrote: ↑

Sat Apr 19, 2025 12:08 am

I agree with Mark. I don’t like 3:1 gears even in a speedster. Except for cruising it never seems to be the right gear. I do a lot of club tours and with the 3:1 you don’t want to get behind a poor running stocker going up a hill in low ruckstell listening to each coil buzz.

Andy

Andy, No.1- my car is a heavy 27 coupe and not a speedster, and No.2 I don't want 3 to 1 gears, but I would like something at least 3.25 to 1 and less than 3.63 to one. I know 13-40 (3.07) is possible. Maybe 12-40 (3.30, and 11-39 (3.54), are too.)

The reason I recommend you consider the standard gear ratio is the fact your car is a heavy 26/27 Coupe. Been there. Done that. Tried the 3:1 and was very disappointed. Went to the 12 tooth. Still not happy. Finally, went to standard and very satisfied with the overall performance. Do not consider using your Ruckstell more frequently to overcome your lack of torque with a higher gear ratio. It was not designed for constant use and will wear out in short order. You have roughly 20-22 horses. Use them wisely.

45 MPH is no problem for a good T engine with aluminum pistons and a stock axle. If you want to go faster for extended periods, get a Warford with an OD gear and a stock axle. A good auxiliary oiler is also a good idea. Aero drag goes up very rapidly as you increase speed over 35 MPH, and it is always present, up hill or down. A coupe with 3.00:1 gears would probably run out of HP before running out of RPM. It might go faster with a stock gearing than with 3:1.

Terry,
I have Ruckstells with 3:1 gears on my 1915 runabout and my 1919 touring.
Both cars have Chaffin's touring cam, aluminum pistons, Reeder or Z head, and run on perfectly tuned coils.

I like the 3:1 gears on the runabout, but have a 12 tooth pinion on hand that I will put into the touring car if I ever need to take the Ruckstell out for some reason. The 3:1's are just a little too tall for a touring car, especially if fully loaded.

I with that I had used a 3.25:1 when I put it together, but at this point, I will not take it apart just to swap out the gear...

YMMV

: ^ )
Keith