Transmission options.

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theawesomeonejr
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Transmission options.

Post by theawesomeonejr » Sun Jul 02, 2017 11:55 pm

Building a 72 Super Beetle, I'm fixing up an 1835 for it right now, and eventually building a 2332 for it. Because it's running a smaller tire, ( I don't have the size right now, but I'll get it if it's important ) and I want to know what tranny and or gearing to use I thought about doing just a freeway flyer till I can build a tranny, or would changing the gears in the stock tranny be better? Gearing options are needed as well. [IMG]//uploads.tapatalk-cdn.com/201707 ... 095943.jpg[/IMG]


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Bad Bob
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Re: Transmission options.

Post by Bad Bob » Tue Jul 04, 2017 1:20 pm

How tall are your rear tires? More importantly, what RPM's are you seeing at cruising speeds? Having tried the "freeway flier", I would rather have the higher RPM and higher fan speed. Keep in mind, my driving conditions are on the freeway with inland So. Cal temps. I would suggest saving your money to buy the transmission you want. Most reliable trans builders will give you good advice on what you should need to handle what ever engine you end up building.

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Marc
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Re: Transmission options.

Post by Marc » Tue Jul 04, 2017 7:18 pm

theawesomeonejr wrote:
Sun Jul 02, 2017 11:55 pm
...just a freeway flyer till I can build a tranny, or would changing the gears in the stock tranny be better?
That question implies that you may not know what a "Freeway Flier" is. As a rule, it's a custom-built trans with the same 4.125:1 R&P as your AH but with the stock .88 4th replaced with a .82 from a Bus. The overall ratio in 4th goes from 3.63 to 3.375, about 7½% taller (with a wider gap between 3rd and 4th which can be annoying at times, like when going up a mountain pass).

When the factory went from a 4.125:1 R&P to a 3.875:1 for the `73-up Beetle, the overall 6% change was partially offset in Fourth by also changing from a .88 to a .93 for a final of 3.60 - the final ratio is taller by less than 1% and the gap between 3rd and 4th is slightly narrower.

The only stock transmission which would somewhat compensate for your smaller tires would be an AN from a mid`70-up Karmann-Ghia - those got the 3.875 R&P but retained the .88 4th, so they're 6% taller than your AH in ALL gears with a 3.41 final in 4th (nearly as tall as the 3.375 "Freeway Flyer" combination). That's about the same difference that a 1½" taller tire would make.

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Marc
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Re: Transmission options.

Post by Marc » Tue Jul 04, 2017 7:19 pm

theawesomeonejr wrote:
Sun Jul 02, 2017 11:55 pm
...just a freeway flyer till I can build a tranny, or would changing the gears in the stock tranny be better?
That question implies that you may not know what a "Freeway Flier" is. As a rule, it's a custom-built trans with the same 4.125:1 R&P as your AH but with the stock .88 4th replaced with a .82 from a Bus. The overall ratio in 4th goes from 3.63 to 3.375, about 7½% taller (with a wider gap between 3rd and 4th which can be annoying at times, like when going up a mountain pass).

When the factory went from a 4.125:1 R&P to a 3.875:1 for the `73-up Beetle "AT", the overall 6% change was partially offset in Fourth by also changing from a .88 to a .93 for a final of 3.60 - the final ratio is taller by less than 1% and the gap between 3rd and 4th is slightly narrower.

The only stock transmission which would somewhat compensate for your smaller tires would be an AN from a mid`70-up Karmann-Ghia - those got the 3.875 R&P but retained the .88 4th, so they're 6% taller than your AH in ALL gears with a 3.41 final in 4th (nearly as tall as the 3.375 "Freeway Flyer" combination). That's about the same difference that a 1½" taller tire would make.

The `73-up transmissions offer some improvements in strength that would be welcome for the 2332, like a stronger first gear. You should be able to get away without those with the 1835, I'd look for a used AN for now and see how the ratios work out for you so you'll know what to order if you buy a "built" trans for the 2332.

theawesomeonejr
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Re: Transmission options.

Post by theawesomeonejr » Wed Jul 05, 2017 1:45 pm

Bad Bob wrote:How tall are your rear tires? More importantly, what RPM's are you seeing at cruising speeds? Having tried the "freeway flier", I would rather have the higher RPM and higher fan speed. Keep in mind, my driving conditions are on the freeway with inland So. Cal temps. I would suggest saving your money to buy the transmission you want. Most reliable trans builders will give you good advice on what you should need to handle what ever engine you end up building.
I'm running a 205/50/R15 rear. I like cruising at 3k rpms which runs me at about 60mph currently. But I want something I can hit a 100mph with but also drive daily. The 1835 is gonna be the smallest size I'll run as far as engines go.


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Bad Bob
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Re: Transmission options.

Post by Bad Bob » Wed Jul 05, 2017 11:26 pm

As Marc suggested, an AN code trans is a cheap way to explore what will fit your situation. Don't be afraid of running a little higher RPM's. My bus ran 3600 @ 65 MPH all day, every day with no problems.

theawesomeonejr
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Re: Transmission options.

Post by theawesomeonejr » Thu Jul 06, 2017 5:04 pm

Bad Bob wrote:As Marc suggested, an AN code trans is a cheap way to explore what will fit your situation. Don't be afraid of running a little higher RPM's. My bus ran 3600 @ 65 MPH all day, every day with no problems.
Thanks Bob. My main reason for wanting higher gears is to prep for the 2332cc that's going to go in it. And I wanna be able to run a decent drag time while also maintaining grocery runner status.


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Bruce2
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Re: Transmission options.

Post by Bruce2 » Fri Jul 07, 2017 2:15 pm

theawesomeonejr wrote:
Wed Jul 05, 2017 1:45 pm
I'm running a 205/50/R15 rear. I like cruising at 3k rpms which runs me at about 60mph currently.
Presumably you are also using a short tire up front. If that's the case, you're only going about 50 mph at 3000 rpm. Your speedo will be way out.
For such a short tire, you need tall gears. A 3.88 with a .82 will still spin the engine pretty fast on the freeway. I bet a 3.44 R&P will put your rpms at reasonable speeds.

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Marc
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Re: Transmission options.

Post by Marc » Fri Jul 07, 2017 3:03 pm

205/50-15 w/4.125 & .88 4th ("AH") => 3173 RPM @60 MPH (3000 @57 MPH), 5288 @100 MPH

3.875 & .93 ("AT") => 3150 @60 / 5250 @100

4.125 & .82 ("Freeway Flyer") => 2950 / 4917

3.875 & .88 ("AN") => 2981 / 4968

3.875 & .82 => 2772 / 4620

3.444 & .93 => 2800 / 4667

3.444 & .88 => 2650 / 4417

3.444 & .82 => 2464 / 4106

I'm running 205/65-16s on my trike (nearly 26½" tall) with a 3.875 and .82 ... that's ~2515 @60 and 4023 @100. If I take 3rd out to 65 MPH (~4000 RPM) I'm at ~2600 when I shift to 4th which is about as low as I want to be under full load. I'm lighter than a Beetle but have worse aero so it's a fairly relevant comparison - personally I wouldn't want to go that tall in a car, even with a 2332 and overdriven cooling fan.

Here's a chart showing my RPM in each gear, with 3.80 1st, 2.06 2nd, 1.26 3rd and .82 4th. Yours would look similar with any ring & pinion ratio (other than the Y axis numbers); for the 205/50-15 tires the RPM numbers would each be 2% higher with a 3.44, 15% higher with a 3.88, and 22% higher with a 4.125.
RPM in Gears (Copy).jpg
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