Gear Ratio

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Model T Ford Forum: Forum 2012: Gear Ratio
Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 06:16 pm:

Is there any way to determine what the gear ratio is in the differential and also a Ruxtell(if that applies)?? Can I find this out without taking the drive shaft out or the differential apart?....Chip


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, August 06, 2012 - 06:47 pm:

Sure, lift one rear wheel with the jack and crank the engine while someone helps you check when the rear wheel has completed two complete turns. (Take the key out of the ignition while testing this) If you turn the crank 3 and 2/3 turns for two complete turns of the single rear wheel, then you have the std Ford gearing with 11 tooth pinion and 40 tooth ring gear = 3.63:1. If you lift the whole rear end and both wheels turn, then you should count the number of turns of the crank for only one full turn of the rear wheels - but that can be hard to evaluate if one of the wheels drags more on the brake shoes than the other, so just one wheel in the air should usually be a better/easier way.

A ruckstell axle has the diff gearing plus a lower gear reducing the diffrential gearing with 0.65:1 making the original 3.63:1 into 5.6:1 when in Ruckstell low.

Other common final drive ratios besides std are 3:1, 3.25:1 and 4:1


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 07:20 pm:

Thank you Roger. I have plenty of flat road speed(almost too much), but have a lot of trouble with hills. What ratio would help me most. The car was built for Florida touring and I live in the Northern NY mountains. My motor runs real strong and has real good compression and the trans. and bands are good. The motor was rebuilt with a "280" cam also.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, August 06, 2012 - 07:39 pm:

Std gears are usually the best for general use in the Model T. 3:1 has been a popular accessory but works best in a light speedster in flat terrain. 4:1 was supplied by Ford for the heavy sedans in the later years, at least in some hilly areas. Your depot hack may be almost as heavy as a sedan if it's a bit overbuilt with lots of wood - hard to tell from your profile photo. Ruckstells and other accessory transmissions were popular in mounainous regions for a reason. Nobody wants to drive mile after mile uphill in low until the left leg gets numb..


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 10:06 pm:

Sounds exactly like my problem! Most hills I can get up in hi gear and low range on the Ruxtell, but on a longer grade I have had to go down to low gear. I dont know how much my hack weighs and I do need to get it scaled. Will 4:1 slow my running speed a lot or just a little?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Monday, August 06, 2012 - 10:11 pm:

George I have the same problem with my '27 now that I brought it up from Florida. It was a real mover in Florida but the Adirondack
Mountains are not friendly to a Model T. I have a Jumbo Planetor transmission on my '14 in Florida that bolts in line just before the rear end and gives you a good intermediate gear for hill climbing and a low-low gear that is good for pulling tree stumps. I really don't need it in Florida so I plan to make the switch as soon as I can get the parts up to NY. If you can find one I think you would be happy with the results and the best part is that most of the guts are standard Ford parts and installation is very simple if you have the shortened driveshaft that goes with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 10:19 pm:

Thanks Val. Got halfway down to Lake George yesterday! We went to the Ticonderoga Car Show. Tough ride down with all the wind. Show was nice, but too many hot rods and muscle cars. My class was from 1900-1959!!! Though class!! Did take a third and had a nicer ride home with the wind at our tail most of the way. Still, a lot of hills!! Hope all is well....Chip


Top of pagePrevious messageNext messageBottom of page Link to this message  By Keith Gumbinger, Kenosha, WI on Monday, August 06, 2012 - 10:27 pm:

Chip - The 4:1 will only slow you down a little. I have that ratio in my '27 Fordor and it really helps there.

Keith


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 11:05 pm:

Thanks Keith.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Monday, August 06, 2012 - 11:12 pm:

What gears do I need for a 4:1 ratio and where do I find them?


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Tuesday, August 07, 2012 - 12:42 am:

Standard crown wheel plus smaller ten tooth pinion i think.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen D Heatherly on Tuesday, August 07, 2012 - 01:33 am:

With 4 to 1 you use a standard ring gear and a 10 tooth pinion. You can buy the special pinions from Langs.

Stephen


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hap Tucker on Tuesday, August 07, 2012 - 08:02 am:

George,

Recommend you also take a look at the Oklahoma web site -- their tech section. It has some excellent factual information on the different gear ratios, heads, cams, and weight and how they influence the ability of the T to climb a grade. From the brief information you have shared, it sounds like your hack may be heavy or you have a lot of heavy people in it, or the engine could use just a little more power or the hills are really steep and long or possibly something else?

The T will never zip up the hill like the large displacement F-150 truck but you should not need to use low pedal much with a Ruckstell and a good engine. Please see: http://mtfctulsa.com/Tech/index.htm and review the
Bill Gent's tips for a good hill climber
http://mtfctulsa.com/Tech/billslist.htm

Power, Torque and Model T Performance
http://mtfctulsa.com/Tech/power_and_torque.htm

Model T Accessory Heads
http://mtfctulsa.com/Tech/heads.htm

Dyno Data - summary of dyno runs
http://mtfctulsa.com/Tech/DynoSummary.htm

I think they will give you some good data to base your next step. If you have not weighed your car -- that would be a good thing to do also. For comparison to other Ford car weights see: http://mtfca.com/encyclo/U-Z.htm#wghts

Good luck and let us know what and how you correct the problem (remember Florida is basically flat from Orlando south.)

Respectfully submitted,

Hap l9l5 cut off


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Tuesday, August 07, 2012 - 09:07 am:

I just scaled the Depot Hack. Normal travel weight for us is 2180#(1/2 tank of gas) This is close to how we travel and includes tools, spare parts, and a few cleaning supplies


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, August 07, 2012 - 09:37 am:

That's more than the shipping weight of the 26/27 fordors - they're listed at 2004# in the encyclopedia: http://www.mtfca.com/encyclo/1926.htm


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Tuesday, August 07, 2012 - 01:07 pm:

Can the pinion be changed without removing and splitting the diff. housing?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, August 07, 2012 - 03:09 pm:

They did when they were new, or only used for a few months. If your ring gear has been used for some time you'll get a better result by splitting the rear end and checking everything up while setting the play and fit of the teeth properly. Unfortunately the repro ring gears are only sold in sets with a std pinion, so if you have to change ring gears you'll have to buy an unneeded 11 tooth pinion too.
(Yep, things were better back before the war when the Ford dealers had the parts..)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Tuesday, August 07, 2012 - 05:18 pm:

Chip, I was registered for the show with my '27 but it looked like rain all day so I decided not to make the trip. I don't know if it rained there but it rained like hell in Putnam where I am. As far as making the switch without opening up the rear, I would be worried about the mesh of the ring and pinion if you made the change without splitting the rear open. I plan to do that when I switch over to the Planetor even though it only involves drive shaft and torque tube replacement.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Button III (Chip), Lake Clear, NY on Tuesday, August 07, 2012 - 06:53 pm:

Roger, Thanks
Hap, thanks for all the great and helpful info.
Val, it did rain for about an hour between 12:30 and 1:30, then it cleared up nice. I guess the gear change will wait until this winter....Chip


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