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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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 Posted: Sat Feb 17, 2018 5:56 pm Post subject: Transaxle and gearing selection |
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I just wanted to toss this question out to collective wisdom here. What gearing do you have and what do you want?
My oval is running the original 36 and a 40 horse transaxle. I think the lower gearing helps the diminutive engine, but I keep the speed down to 65 mph tops (OK, a few seconds at 70) because it raises the rpm in 4th around 7%. I noticed that a tunnel trans with a 4.125 R&P would be pretty close to stock. A lot of people seem to like running a full syncro with the 36 and I understand that.
Has anyone done any custom gearing for their 36 horse? I thought that a tunnel trans with a 4.125 and 40 horse 1.32 3rd and 0.93 late 4th might be nice. Shorten the 3-4 jump and put the 4th gearing close to a 40 horse box.
Another thought is to use the '60 splitcase 2nd in the rebuild of an oval box. It was 1.94 instead of 1.88. Not a big change but handy when lacking a syncro in 1st.
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Bruce
Samba Member
Joined: May 16, 2003
Posts: 17290
Location: Left coast, Canada
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| Posted: Sun Feb 18, 2018 7:51 pm Post subject: Re: Transaxle and gearing selection |
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| EVfun wrote: |
| ..... a tunnel trans with a 4.125 and 40 horse 1.32 3rd and 0.93 late 4th might be nice. |
This is not a bad idea, but you have to take into account that not all parts fit all years without modifications. Using the .93 top gear means you're using the late 9 tooth mainshaft and the late 3-4 hub and gear carrier. The 1.32 then needs custom machining to fit the late mainshaft. IOW, it adds $$.
My recommendation is to use 40hp gears. Compared to your suggestion above, the 40hp trans will be lower geared in 1st through 3rd.
A benefit to your suggestion of a 4.12 gearbox is the taller 3rd works better on the freeway. When you get the slightest grade with a 36hp engine, you have to gear down. The taller 3rd lets you go a bit faster.
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Mon Feb 19, 2018 4:55 pm Post subject: Re: Transaxle and gearing selection |
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I didn't realize the work to put the 40 horse 3rd with the late 4th. I have such a box in my garage but with a 4.375, built about 25 years ago by Transform. That combo would be too low geared for stock tires, but it got me thinking.
Another option that would be similar in 3rd and 4th would be a 40 horse box with a 1.26 later 3rd. It would have the advantage of closer 3-4 gearing jump than stock 36 or 40 horse boxes.
At that point just using a 4.125 swingaxle box starts to look easier, keeping the advantage of the closer 3-4 gear spread but not the advantage of lower gearing in high (or not, depending on one's view). I find the 36 a little happier on Seattle area freeway grades with some extra rpm in high.
I'm surprised more oval owners haven't picked their gears because a number have chosen to switch to full syncro transaxles.
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| As a general rule, cheap parts are the most expensive parts you can buy. |
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txoval
Samba Member
Joined: January 23, 2004
Posts: 3552
Location: The Woodlands, TX
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| Posted: Mon Feb 19, 2018 5:57 pm Post subject: Re: Transaxle and gearing selection |
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EVFun:
Before I sold my 54 I was looking at having a custom transaxle built with different gear ratios to match the attitude of my modified 36HP engine.
Needless to say, the non-stock 3rd and 4th gear options are not cheap. I may have the spreadsheet I was looking at to decide which way to go, if you want me to send it to you, shoot me an IM.
The transaxle would have been close to $2000, before shipping |
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