Rear Gear Ratio

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Model T Ford Forum: Forum 2012: Rear Gear Ratio
Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Sunday, July 29, 2012 - 10:44 pm:

Hey guys,
Im waiting on lots of parts to rebuild my rear axle. I have everything to do it but a pinion gear. I have the new ring gear coming and all the hardware. My question is, Which tooth pinion should I get. It has a 11 tooth on it now but I was curious about using a different tooth count. The ring is a 40 tooth. If anyone has a cheap gear for sale with little to no use id be very interested. If not whats a good pinion to use with what i got. Thanks guys.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Conklin on Sunday, July 29, 2012 - 11:07 pm:

If you have a standard T with out any auxiliary gear boxes stay with the standard ratio. Remember that changing the gear ratio also effects your braking ability, unless you have auxiliary brakes and even then you feel a difference.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Sunday, July 29, 2012 - 11:20 pm:

Thanks Don. I found a 12 tooth for ten bucks and am curious if I could use it. The new pinions are a bit more expensive. Any reason to not go ten or twelve.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, July 29, 2012 - 11:21 pm:

We can't see your car from here. That makes all the difference.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen D Heatherly on Sunday, July 29, 2012 - 11:25 pm:

I would leave the ratio stock, use an 11 tooth pinion.

Stephen


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Conklin on Sunday, July 29, 2012 - 11:37 pm:

Unless you have a light car, I wouldn't do it. The resulting gear ratio has the potential to raise your cruising speed about 9% if you have the power to pull it. It will also definitely reduce your braking and hill climbing ability.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Sunday, July 29, 2012 - 11:55 pm:

Is a 1925 touring, Im just curious because the availability of cheap pinion alone is hard to find. Im looking if anyone has any leads on the 11 tooth. How about using a 10 tooth, would that just make it slower and better at hill climbing or is 11 really the only way to go.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Monday, July 30, 2012 - 12:19 am:

Brandon, Where did you purchase your ring gear? The new reproduction ring and pinion gears are normally made and sold as a matched set, however, certain pinion gears can be substituted for the standard Ford 11 tooth pinion and will work fine if set up properly with the right clearance. The 10 tooth pinon was a Ford option, turning the 3.63 standard ratio into a 4.00 to 1 mountain ration. Other combinations are possible if you are using a 39 tooth ring gear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, July 30, 2012 - 12:21 am:

Why do you think you are able to find 10 tooth and 12 tooth pinions so cheap? Been there - done that - stay stock is my advise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Monday, July 30, 2012 - 01:15 am:

I already found a good looking 12 tooth on ebay, and theres a nice 10 tooth on there as well. I got the ring from a old model t and antique parts guy. New is too expensive, and I have everything else on the way. I just wanted to know if I could use a different pinion with a standard 40 tooth ring gear. Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Monday, July 30, 2012 - 08:48 am:

Brandon -- The standard rear gear ratio of 3.64:1 is great for all-around Model T driving. This is with an 11 tooth pinion and 40 tooth ring gear.

The 12-tooth pinion gear will net you a 3.25:1 rear gear ratio, which is too tall for most Model T's but you need to use the 39 tooth ring gear.

The 10-tooth one will give you a 4:1 ratio, which will drop your top speed a bit but give you more power for climbing hills.

That could be a good thing, depending upon where you drive your T and how heavy the body is. Either of them should be compatible with the standard ring gear.

Ed. note fixes ratios


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Monday, July 30, 2012 - 08:55 am:

Thanks Mike, I needed a good vote. I drive a four seater touring. I said "drive" I meant to say start and run on blocks. If I can get this cheap pinion it will kick start this recovery from the last 8 years of sitting and waiting on parts. Might actually get to roll on a road. I have had this beautiful car just waiting for me for too long. Thanks again guys.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel D. Chicoine, MD, Pierre, SD on Monday, July 30, 2012 - 09:30 am:

Brandon, I think Mike has it backwards. the 10 tooth with a 40 tooth ring gives a 4:1 ratio that might be better for climbing hills and for heavy cars. You may sacrifice top end although maybe your car will rev higher and maintain the top end.

The 12 tooth, which I'm presently putting into a Ruckstell, will raise the ratio to 3.25:1 (with a 39 tooth ring gear) and "may" give you a few more MPH but only if your engine is strong and your car is not heavy. Otherwise, you will likely be disappointed with slower accelleration and harder braking.

You will also need to put in a recessed ring gear, made for the 12 tooth, and shim it up, since the 12 tooth is a larger diameter.

Also with both the 12 & 13 tooth pinions you will need to disassemble the pumpkin to remove the drive shaft as both these pinion gears won't fit into the hole in the diff without splitting the differential halves.

I have a strong engine with Z-head, .280 camshaft, and a high volume intake, along with a Ruckstell that has an underdrive for climbing, as well as auxilliary Rocky Mountain brakes so I believe I can use the higher ratio. I may be disappointed! The general consensus is that the 11 tooth pinion with 40 tooth ring standard ratio is really the best for the vast majority of most T's.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Monday, July 30, 2012 - 10:03 am:

Others have mentioned it but it bears repeating that your 40 tooth ring gear won't work with a 12 tooth pinion. You need to have a 39 tooth pinion the one that goes with the 3 to 1 gearset. Expensive.
Both the 10 and 11 tooth pinion will work with a 40 tooth ring gear, though.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Keith Gumbinger, Kenosha, WI on Monday, July 30, 2012 - 12:01 pm:

The 10 tooth pinion gear and the 40 tooth ring gear = 4:1 ratio were standard on the heavier sedans from '25 through '27's. The sedans are several hundred pounds heavier than the tourings and roadsters and they need this lower ratio.

Keith


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Monday, July 30, 2012 - 01:48 pm:

Thanks for all the feedback guys. I found a nice 10 tooth that will work nicely. Talk to me about "recessed ring gears" Im doing this project myself in the garage without any literature. I do have a rear axle book coming in with the parts. The ring gear thats coming in was not specific as to recessed or not but as a 40 tooth ring. I checked it out and at the same time looked all over what ring I have and they look to be a match. Ill know more soon.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Monday, July 30, 2012 - 01:51 pm:

Sorry guys -- I knew that. I must have been having a "senior moment". :-)

Fixed it Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Brancaccio - Calgary Alberta on Monday, July 30, 2012 - 02:37 pm:

Guys, I did a bit of editing on the above to clear up a bit of the confusion.

To be clear with the stock 40 tooth ring gear you can use a 10 or 11 tooth pinion.

With the 39 tooth gear you can use the 12 or 13 tooth pinions.

I also believe the 39 tooth ring gear is recessed in order to allow the teeth of the gear to mesh properly with the pinion.

Chris


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, July 30, 2012 - 03:55 pm:

I am familiar with Tigard area and there are many hills to pull out in the country around there. I would recommend a standard ratio even with a Ruckstell. You could go for a Warford with under and overdrive if you want a higher ratio for cruising, but the problem is when you start out on a hill, even a small grade with a higher ratio, it puts a lot of strain on the low band to get it moving unless you always shift the rear axle down before starting out from a stop. I also have found hills here in the San Diego area which I must use low low to climb. It is likely, you might not be able to climb one of those hills even with Ruckstell if you use a higher ratio. One of mine has a higher ratio and it is a roadster, so the car is quite lightweight, but I definately notice the difference.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Monday, July 30, 2012 - 04:28 pm:

From Fahnestock or one of those. As seen below, Beware, not all 10 tooth pinions were made by Ford. Non-Ford ones require a special ring gear.



rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dale Peterson on Monday, July 30, 2012 - 04:29 pm:

Brandon, A word of caution on your choice of gears. Old gears are cut a little different from the newer gears now available from the suppliers. Mixing the two results in a noisy rear end. I learned this the hard way.
I have had all three in my '15 Touring with High comp pistons, otherwise stock; 3:1 with the 13 tooth pinyon and 39 tooth ring gear in a Ruckstel, standard 11 tooth pinyon with 40 tooth ring gear in a stock Ford rear end, and finally 10 tooth pinyon with 40 tooth pinyon in the Ruckstel.
My experience is; first that it is highly advisable to follow the advise of other posters on this forum, use the Fun Projects adjustable modern bearing spool. It makes installing and adjusting the drive line so much easier. Working on the rear end is a real pain when you have to split the housings to get the pinyon out or to adjust the mesh. It is possible to adjust the mesh without disassembling the rear end!
The stock gears are a good all around choice. The 3:1 ratio of the 13 and 39 set makes for a lot of shifting into low Ruckstel whenever you are driving into any wind, or up moderate hills. The other cars on tours were always leaving me behind because of these conditions in the west. The 10 and 40 set was installed because I had the rear end apart and wanted to get rid of the 13 and 39 and the 11 tooth was not available. This is when I learned the truth about mixing new and old cut gears! I have found that the 10 and 40 is actually good with the driving we do. It is a little slower, 30-35 on the flat as apposed to 35-45 with the 13 and 39, and 35-40 with the 11 and 40. Now I keep up well with the other cars in our club (lots of longer tours) on the hills, others don't complain that I am driving too fast, but they may still get ahead of me at times on the flat.
But what are we trying to do by driving fast anyway? Isn't this a Model T Ford club, and don't we like "Life in the Slow Lane" anymore? Maybe those that want that go fast feel should think of moving on to the "A."


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brandon French-Tigard, Or on Monday, July 30, 2012 - 10:29 pm:

Thanks for all the great feedback guys, always appreciated. I found a 11 tooth for 45 from model t haven in kansas. Thanks again.


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