Hi all, i have a 24 roadster and live in Los Angeles..am considering changing to rear end gears to 3-1 ratio. Can anyone tell me the pros and cons? Car has a z-head and a distributor. Also will be adding ac brakes.
Poorer engine braking
Better top end, if the engine will support it.
3-1 gears are commonly recommended for lighter cars with a Ruckstell or maybe an other axillary trans. I would not recommend 3-1 gears with only he standard trans. There is not a lot of mountains in LA but you would still be driving a lot in low gear.
Jim nailed it. Fine for a light car IF you have a Ruckstell or aux trans. Probably pretty disappointing with an otherwise standard driveline unless you only drive on the flat.
Hey John, what carb do you run?
Hi Seth,am running a NH with a high-vol intake.She scoots as is but sometimes we have to hit the freeways here.
Before you change the rear-end gears, invest in a new carb. The NH is a great all around carb, but it's no Stromberg OF or Zenith S4BF. I don't know if you drove the car before it had the Z head, but I guarantee you'll feel an instant difference in the top end and acceleration the same way the Z head changed things. I thought I added 15 more HP the first time I drove with my Zenith carb.
As for the rear end gears, if you add the new carb first, I think you'll be fine. It doesn't really reduce the driveability of the car so much as drastically change it. Do you ever tour with a group of other T's or antiques? The biggest gripe I hear about the 3 to 1's is that it makes it hard to tour with other T's. When everyone is going around 30 mph up a small hill, you won't be able to lug along with them in high, you'll have to slow down and race the engine in low gear. If you mainly drive by yourself, you'll be able to maintain enough speed to get up the little hills in high.
I think the only advantage is faster on level or downhill.
9 years ago we had a national tour here and the hotel location was at the top of a grade. The grade could easily be climbed in a standard T unless you had to slow down because of slow moving traffic. The grade was even more easily climbed with Ruckstell. However there were a few cars with 3-1 gearing who parked their cars after the first day and rode with others. Those cars ran well in places such as Kansas, Nebraska or other flat areas, but the drivers got tired of holding the low pedal for 5 miles going uphill. I live in Southern California and have one car with a 3-1 which was in the car when I got it. The other two have standard with Ruckstell. The two with standard gearing climb all hills very well. I took one last September to Yosemite and went right up to Glacier Point.
The problem with a Model T going fast is not only the gearing, but also the brakes and the high center of gravity and wood spokes. The steering also gets a bit squirrely when going fast.
The car was made to go about 30 mph and can go up to 40 with standard gearing. Any faster, is in mho risky.
I'd say stay with Std. unless you have a Ruckstell. That's what's in my car.
George n L.A.
I think 3:1 gearing is a mistake unless you have a speedster body or one stud of an engine or a tranny. this is particularly true if you have hills in your area. I would look into getting a new warford tranny.
From your profile this looks like your first day of posting on the forum – although you already have 5 postings so far. Welcome to the forum! Please also share a little about your background – i.e. is this your first T, you have had several, or you have always been around Ts etc. Also your car background as many folks are experienced with other types of cars and then purchase a T etc.
There is an excellent group of articles on the Tulsa Model T Club web site that discuss power, gearing, etc. Ford could have used any gear ratio he wanted in the Model T and for many locations and body styles the stock gear ratio is really great. The articles address the difference in climbing ability between the different rear axle ratios etc. They also talk about reducing weight to increase hill climbing capability. That works not only with swapping out a Sedan body for a roadster body like yours but also by having a light 125 pound driver and passenger (those days are long gone for me) verses really large folks.
They have a good analysis and description of comparing the rear axle ratio, raising compression, changing cam, adding a Ruckstell etc. Their site is at: http://mtfctulsa.com/ Their Tech page is located at: http://mtfctulsa.com/Tech/index.htm
Power and Torque – is the title but scroll past the first part about cams down to the “High Speed Gears” where they share that reducing the weight by 150-200 pounds increases the maximum hill climbing grade by 1 per cent etc. http://mtfctulsa.com/Tech/power_and_torque.htm#References They compare the 3.64:1 (standard), 4:1 (10 tooth pinion), 3:1 and 5.6:1 (3.64 in Ruckstell low) rear axle ratios.
Dyno Data - summary of dyno runs at: http://mtfctulsa.com/Tech/DynoSummary.htm
Head info: http://mtfctulsa.com/Tech/heads.htm
Fred Houston's 12 steps to a good running Model T for touring http://mtfctulsa.com/Tech/fredslist.htm
While you didn’t ask, there is an excellent article on the Model A Fords that explains why we need to do things that work together to improve the engine performance rather than just putting all our efforts into a single “one really big thing.” Frank used the illustration of putting the two large carburetors on a stock VW bug and gaining little performance and dropping the gas mileage a lot in one of his older postings. It also discusses why doubling the compression ratio normally will not double the horsepower. In theory it will – but theories seldom work perfectly in the real world. See: http://www.amuffler.com/dyno/dyno1.htm
Again welcome to the forum. If you are also new to Ts – let us know and we will point you to some safety “gotchas.” They are not a reason to avoid the T but they are all good reasons to respect a T. And they are all manageable – it just helps to hear or read about them rather than experience them all first hand. And don’t forget to check out the local T chapters near you.
Good luck with your roadster!
Hap l9l5 cut off
I did this years ago. My thinking was, "see how much faster it would go with 3:1" Was I wrong. What I had was a down hill rocket but a up hill fizzle. All I really accomplished was to lower the RPM with no improvement in performance. I finally found a Warford underdrive. That solved the problem.
As I recall with the lower ratio pinion/ring set the pinion won't go through the hole in the rear end housing. Every time you want to work on the rear end you will have to split the pumpkin... a lot more work and a lot more mess!
Once I broke a 10 tooth pinion in my pickup (it had 4:1 rear end at the time). The gear spread out a little bigger and I couldn't get it out of the pumpkin... I had to split the rear to pull the drive shaft and pinion... that is a real pain it the ... um... neck!
I feel that this problem offsets any advantage you might think you are getting with that lower ratio... IMHO.
Hi Hap and all who responded. I really appreciate all the help.I have been a MTFCA member for bout 20yrs now. I am 44yrs old and have had 5 T"s. Have a 24 roadster and a 27 Tudor.Have been in the car business since i was 14 yrs--from beign a tech to working in a machine shop ect.My dad got me into T"s watching 8mm Laurel &Hardy films --I still do with my kids.He came from Greece and was born In 1924 so he taught me alot of hands on work.Based on all the info here , I am going to leave her alone and just enjoy. Again, thank you to all!!
Hi John I run the 3 to 1 in my 15' roadster and overall love it. My main reason for running this gear combo is so that it slows the RPMs down in high. RPMs are a killer of T engines Yes your engine will need to run strong and I would not run it without a ruskstall, But I live in seattle area and it is not flat land. I have no issues with preformance or keeping up with anyone yet. The only negitive is as Seth said you will be running your own race when touring with other T's. Running down hills faster than everyone else is not a good thing.
Before making a T go faster, you need to make it stop faster.
If the engine is fairly well balanced, high rpm aren't so bad.
I had 3 in one gears in my 27 cpe here in TN. Car ran fine (has Ruckstell), managed hills including Look Out Mtn. but was a problem on tours because I could not run with the pack, too slow and bogged down. Was great for solo running and as Ricks says, you must have braking to go with it!
I have 3:1 gears and a Ruckstell in my 1910 Touring. It has the stock original engine. I love it! We (me, wife, and 2 kids) have toured all over with it. We live in Kansas so it allows us to go a little faster on flat ground (or same speed with lower RPM's).
We have also climbed Pikes Peak with absolutely no problem last summer. I never used Ruckstell low with transmission low. I never had to shift that low.
We toured Vermont this summer and climbed some good sized hills (small mountains) with no problems.
Stay away from 3 to 1 . Every person I know of in the Denver Club that tried 3 to 1 except one hated them and took them OUT. Not only could they not keep up with the rest on a slight up hill, They were powerless at the signal lights. 3 to 1 may be OK in a small town in Kansas with few signal lights, but is miserable in most places.
I might agree with Dave above except that I have a Speedster. I love my 3:1 gears. I go 25+ at idle on the flats. It might take me a bit to get going, but once I am moving I am having fun.
If you have a coupe, tudor, or sedan, I would stay away from 3:1. Touring or roadster might be OK.
The power band of a Model T is awfully narrow. As you engage the low band, you've got the throttle set for maybe 700 RPM (I'm guessing) and normally, you'll shift up at around 1,200 or 1,300 RPM. At that point, volumetric efficiency has decreased tremendously and the engine doesn't want to rev too much higher (and with an unbalanced crankshaft, that's just as well). So, okay, that gives you five or six hundred RPM to play with and that sure ain't much. Somewhere in the middle of that short band is the car's comfortable cruising range: about 25 to 35 mph and, not surprisingly, the "sweet spot" is right in the middle at 30 mph.
Let's look at it another way: Right after you up-shift and open the throttle, your engine feels and sounds like its lugging. The car vibrates at a low frequency that makes your mirrors shake badly enough to be useless (and it may be that the Model T was built to tolerate that, but even so, vibration never made any machine last longer). Nobody likes that low, lugging section of the engine's power band. You can deal with it by accelerating very, very gently, which will minimize its intensity, but increase its duration (and cause the cars behind you to become impatient); you can power up and blast through it quickly, which will decrease the duration of the vibration, but increase its intensity; or you can compromise between the two.
In an otherwise stock Model T, gearing up the rear end to a 3:1 ratio is going to expand the low-frequency vibration section of the power band and make the lower end of that section worse. In other words, after up-shifting, the car is going to accelerate poorly and rattle & shake until you've built up a good deal more speed than would be the case with normal gearing. In a stripped down, 2-seat speedster that has no body and a whole lot less weight, that effect will be minimized. A 3: 1 geared Touring with even a moderate load (let's say two people and a full tank) would be just awful going uphill.
Assuming a healthy engine, 3:1 gearing should increase your cruising and top speed on level ground and that means nothing because 40 mph, which my normally-geared Touring can already do, is too fast for the Model T's wooden-spoke wheels, too fast for its laughable brakes and negligible tire traction, and too fast for the ratio at which the car's steering is geared. Any non-performance car that is operated at or near its top speed is at the brink of control loss. Forget about making a Model T go fast. It's not supposed to.