3 speed to 4 speed conversion - Impala Tech
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post #1 of 10 (permalink) Old 05-13-2010, 09:09 AM Thread Starter
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Location: Ft. Wayne, Indiana
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3 speed to 4 speed conversion

Hello everyone! I am wondering if anyone has ever converted a 3 speed manual tranny over to a 4 speed manual? (I am working on a 1964 with a 327 3 speed on the floor) My concerns are if I have to change the or modify the crossmember? Driveshaft? Rear end gears? Bellhousing? I am just toying with the idea and do not want to do anything that could not be easily switched back, it's a very original car, but the un-synched 3 speed sucks sometimes. THANKS for any input!!!

'64 Impala 2 door, tuxedo black, blue interior
327, 3 speed manual. Original Paint, interior, etc.
Bought new in '64 by my parents!
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post #2 of 10 (permalink) Old 05-13-2010, 09:17 PM
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All yopu need is a new shifter and a four speed as the three speed is on the tree and four speed is on the floor. Other-wise it a is a straight swap with nothing else on the car changing (assuming you have the same number of splines on the input shaft). I have swapped about twenty Camaro sixes over to BBC four speeds that way (just add decals and instant SS car)

Big Dave
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post #3 of 10 (permalink) Old 05-21-2010, 08:35 AM
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My 67 Camaro was a 3 speed originally and I put a 4 speed in it many years ago. Piece of cake with a new shifter.

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post #4 of 10 (permalink) Old 05-27-2010, 08:17 PM Thread Starter
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I have a Muncie M20 with a Hurst Comp Plus on it, looks like it should be a breeze if I decide to do it. I'm just not real crazy about the 3 speed, even though it's 'correct'. No one mentioned the driveshaft, so I take it that it bolts right up without shortening it or anything?

'64 Impala 2 door, tuxedo black, blue interior
327, 3 speed manual. Original Paint, interior, etc.
Bought new in '64 by my parents!
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post #5 of 10 (permalink) Old 05-27-2010, 09:13 PM
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Quote:
Originally Posted by 1owner64 View Post
I have a Muncie M20 with a Hurst Comp Plus on it, looks like it should be a breeze if I decide to do it. I'm just not real crazy about the 3 speed, even though it's 'correct'. No one mentioned the driveshaft, so I take it that it bolts right up without shortening it or anything?
You are correct the only modification to the car to swap from a three speed to a four speed manual is a shifter change. You could reuse the old three in a tree shift mechanism but you would never be able to get the car in reverse.

Big Dave
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post #6 of 10 (permalink) Old 06-29-2010, 01:45 PM Thread Starter
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Looks like the older 3 speeds are indeed different, about 4" shorter than a Muncie 4 gear. I have a 'wanted' ad placed in the classifieds looking for a decent used driveshaft for my application. There is a local company that can manufacture a new one, but it is salty as far as costs. I will go that way if I have to......

'64 Impala 2 door, tuxedo black, blue interior
327, 3 speed manual. Original Paint, interior, etc.
Bought new in '64 by my parents!
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post #7 of 10 (permalink) Old 06-29-2010, 02:20 PM
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Sounds like a long tail shaft short tail shaft thing. The factory makes two diferent transmission lengths on automatics a 9" long tail shaft and a short tail shaft that is only 6" long. The long tail shaft is used in B-bodies and pick-up trucks only. Everything else gets a short tail shaft. I have never seen a long tail shaft four speed Muncie before, so I wasn't aware they even existed. Sorry for the bad advise.

Big Dave
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post #8 of 10 (permalink) Old 06-29-2010, 07:15 PM Thread Starter
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No problem at all, you were doing your best to help! Thanks again!!!

'64 Impala 2 door, tuxedo black, blue interior
327, 3 speed manual. Original Paint, interior, etc.
Bought new in '64 by my parents!
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post #9 of 10 (permalink) Old 07-29-2010, 08:55 PM Thread Starter
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4 speed is installed!

It is like having a totally new car! Driveshaft had to be shortened by 4", otherwise, it was a breeze. Never fear, each and every original piece is safely stored away. My Dad (the cars original owner) and I talked about this switch over before he passed away last summer, and he was fine with it. He had even said that to do over again, he would have checked the box for a 4 speed on the option sheet in '64, so there was no 'guilt' involved.

'64 Impala 2 door, tuxedo black, blue interior
327, 3 speed manual. Original Paint, interior, etc.
Bought new in '64 by my parents!
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post #10 of 10 (permalink) Old 07-31-2010, 10:04 AM
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I have the original driveshaft from my 4 speed 64 SS in storage. Great shape if anybody needs one. [email protected] put driveshaft in the subject
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