3-Speed with Reverse Transmission Ratios?

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eazye727
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3-Speed with Reverse Transmission Ratios?

#1

Post by eazye727 » Tue Nov 13, 2007 6:23 am

Hey everyone! I'm new to this forum, but it was recommended to me as the best place on the web to get tech questions answered on vintage Harley topics because it had the most knowledgeable members.

I've already searched the web and this forum extensively and haven't found the answer to the following question:

So here goes..... Does anyone know the 1st, 2nd, 3rd, & Reverse transmission OEM gear ratios for the 3-Speed with reverse transmission that was used on Harley Big Twins from 1933-76 on the Knucklehead, Panhead, and Shovelhead?

Notes: I have been told the Big Twin 3-Speed with Reverse transmission is completely different and not interchangeable with the 45" Servi-Car 3-Speed with Reverse. The Big Twin 3-Speed was an optional transmission alternative to the standard 4-Speed without Reverse and was provided for use with a Sidcar. The 3-Speed with Reverse shift patterns (from front to back) of motorcycle are:
1933-46: R-1-N-2-3
1947-76: 3-2-N-1-R

Thanks in advance for everyone's help!



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#2

Post by panhead » Tue Nov 13, 2007 8:11 am

Look here for the data:

http://www.hydra-glide.com/panhead_facts.php

and here for Jack Hester's program to calculate the ratio's:

http://www.terra-glide.net/pgms/WheelSpeed.exe

eazye727
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#3

Post by eazye727 » Wed Nov 14, 2007 3:39 am

Thanks Panhead! That second link answered my question perfectly!

I've been told the 3-Speed with Reverse case is the exact same case as the 4-Speed. Is this true?

I ask because I am having such difficulty locating a 3-Speed with Reverse transmission that I am considering using a 4-Speed case and buying the 3-Speed with Reverse internals to put in it and thus building my own. I am especially considering the RevTech P/N 58299 case that is meant to replace the 1936-64 4-Speeds and it appears to have the reverse idler shaft mounting holes already drilled in it. This Revtech case is meant to be used with a 1952-79 Ratchet Top. Will the Ratchet Top be able to correctly shift the gears of the 3-Speed with Reverse?

The only 3-Speed with Reverse transmission I have ever seen an actual picture of was from a 1954 Hydra-Glide Panhead with the hand shifter so it had the Jockey Top. Did the 3-Speed with Reverse ever use another OEM top(s) and a foot shifter?

Also, did the 3-Speed with Reverse case grow ears 1965-76 to support the electric start and aluminum primary like the 4-Speed case did?

Thanks again for all your help!

eazye727
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#4

Post by eazye727 » Sun Dec 02, 2007 3:44 pm

Does anyone know the answers to my questions in my previous post?

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#5

Post by panz4ever » Sun Dec 02, 2007 6:52 pm

Part number for the hand shift 3 spd/reverse is34804-36; part number for the foot shift is 34805-52....definitely two different tranny covers. Do you have a source that will show what they look like (parts manual)?

You also need a different shift drum, shift fork for for the countershaft, countershaft reverse gear, countershatft low gear (for 3 spd/reverse), countershaft gear (19 tooth for 3spd/reverse), mainshaft low and reverse gear (hand shift) and mainshaft second gear (handshaft). You already are of aware of the need for the idler gear and shaft.

I cannot answer if the late cover can be used for what you want, although with the knowledge on this forum I am sure someone has done it or figured out how...

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Re: 3-Speed with Reverse Transmission Ratios?

#6

Post by Scott McKelvey » Thu May 05, 2016 4:01 am

Old thread but valuable and relatively uncovered info. The following is based on my limited experience for 36-76 big twins.
1) case- same BUT it's machined for the reverse idler gear and shaft
2) gears- there's a few internal differences which the manual covers. But basically it's the 1st-2nd gears on both main and countershafts.
3) shift stuff- countershaft shift fork is unique.
4) Top and shift drum (to my knowledge) will not only work in the hand shift top. BUT, to my knowledge, the handshift top is interchangeable with any ratchet top (if the internals are correct).

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Re: 3-Speed with Reverse Transmission Ratios?

#7

Post by kitabel » Thu May 05, 2016 4:31 am

And no, neither of those 2 links contained the 3 speed ratio information he requested.
The big twin 3 speed ratios are:
1st 2.708:1
2nd 1.497:1
3rd 1.000:1

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Re: 3-Speed with Reverse Transmission Ratios?

#8

Post by RUBONE » Thu May 05, 2016 2:11 pm

Old thread but valuable and relatively uncovered info. The following is based on my limited experience for 36-76 big twins.
1) case- same BUT it's machined for the reverse idler gear and shaft
2) gears- there's a few internal differences which the manual covers. But basically it's the 1st-2nd gears on both main and countershafts.
3) shift stuff- countershaft shift fork is unique.
4) Top and shift drum (to my knowledge) will not only work in the hand shift top. BUT, to my knowledge, the handshift top is interchangeable with any ratchet top (if the internals are correct).
1, Not all cases are machined. Some later cases do not have the hole for the idler and case must be changed.
2, Gears, all are different except the main drive gear. Low cluster, CS cluster,etc.
3, correct, the offset shift fork is for the sliding gear.
4, handshift drums will not fit ratchet tops, and ratchet tops do not work with 3 speed or 3&R. 3 speed and 3&R are handshift only.

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Re: 3-Speed with Reverse Transmission Ratios?

#9

Post by kitabel » Fri May 06, 2016 4:24 am

3 speed components:
Main drive gear 26 teeth
Countershaft gear 15 teeth
Main drive multiplier: 26 / 15 = 1.7333:1
1st gear mainshaft 16 teeth
1st gear countershaft 25 teeth
1st gear ratio: 25 / 16 X 1.7333 = 2.708:1
2nd gear mainshaft 22 teeth
2nd gear countershaft 19 teeth
2nd gear ratio: 19 / 22 X 1.733 = 1.497:1

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