Auto to 4-speed Transmission Swap
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Thread: Auto to 4-speed Transmission Swap

  1. #1
    Opeler
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    Auto to 4-speed Transmission Swap

    I've had my '71 GT for about 13 years. My only regret with this car is it has an auto transmission. Recently I found a donor car to get a 4 speed and other items needed to make the swap. I also have the list from the Opel Motorsports Club's website (I am a member) of all items needed. I also tried to contact OMC about reprints of several relevant articles (have not heard back from them, yet). A search through the threads on this web-site found several discussions of making the swap. Is there anybody out there who has actually has made this change? I'd like to talk with you about the procedure. I have a good friend who is a BMW mechanic who is going to help me, but any hints before starting would be appreciated.

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    Bikini Inspector Frozen Tundra GT's Avatar
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    OGTS has back issues available for cheap.

    Thats all I got for ya.

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    UngerDog ungermm's Avatar
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    I did the auto trans to manual conversion about a year ago. I remember that the biggest head scratcher was trying to figure out why my clutch cable had so much slop in it. Well, because the body of the GT from a auto transmission car didn't come with the spacer at the firewall. It is labeled as GT Sleeve here...

    http://www.opelclub.com/Transmission...MarApr2008.pdf

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    Opeler 69whitegt's Avatar
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    I switched mine from an automatic to a 4 speed last summer. Wasn't bad, just don't forget to remove the spacer that is in between your flex plate and crank shaft. Mine was a PITA to get off, I had to heat mine with torch to remove it.
    ____________________________
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    . 5 speed Getrag, ditched 4 speed in 2016, ditched the factory TH180 in 2012.
    . Isky OR-66 camshaft

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    Tennessean Site Supporter hrcollinsjr's Avatar
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    Procedure is relatively straight forward especially if you have a donor car.

    Harold

    P.S. Don't forget to install a pilot bearing in the crankshaft end for the tranny input shaft.

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    OpelGT.com Übermoderator kwilford's Avatar
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    For my effort and money, I would swap to a Getrag 5-speed, since you already have the requisite auto driveshaft (which needs to be shortened).
    Keith Wilford
    Finishing up a bare-metal, nut & bolt rotisserie restoration of my '71 Opel GT

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    Tennessean Site Supporter hrcollinsjr's Avatar
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    Quote Originally Posted by kwilford View Post
    For my effort and money, I would swap to a Getrag 5-speed, since you already have the requisite auto driveshaft (which needs to be shortened).
    Maybe, BUT the donor car probably cost less than a 5-speed and chasing down all the parts for the conversion from an auto to a manual. The parts car may have been needed for other reasons than just the conversion and/or it may get parted out to recoup some of the money spent. Once the auto to manual is done it's a simple matter at a latter date to change to a 5-speed if the owner desires to.

    Harold

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    Southern Red Neck BQS4's Avatar
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    Quote Originally Posted by kwilford View Post
    For my effort and money, I would swap to a Getrag 5-speed, since you already have the requisite auto driveshaft (which needs to be shortened).
    I hate to differ with Keith, but, having done a conversion or two on both the GT and the Manta/Ascona, I have found a few things out the hard way, The GT auto driveshaft is actually TOO SHORT, for the 5-spd conversion, BUT, you do need the auto yoke and a 4-spd driveshaft. Shorten the 4-spd shaft to 9.75" (9 3/4") center-of-weld-to-center-of-weld, and put the auto yoke on that, balance, and you're good to go.
    "Yes, I do have a rifle rack in my Sportwagon"

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    Opeler
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    I will add to my original post, the donor call was free! I just have to "flatbed" it from its current location, stuck in several inches of dried mud behind a barn.

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    Tennessean Site Supporter hrcollinsjr's Avatar
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    Quote Originally Posted by Larry View Post
    ...,stuck in several inches of dried mud behind a barn.
    You sure it's just mud?

    Harold

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    Opel Tinkerer and Rescuer GoinManta's Avatar
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    I need the clutch pedal assembly for a Kadett.. I am getting closer to going ahead and swapping for a 5 speed myself as I may be getting a new GT that was an auto and is missing its transmission.

    BTW.. any spare parts (Interior the shifter, etc.. that is for a GT) I would love to get when your finished. I plan on keeping the GT an Automatic, and converting my Kadett.
    CURRENT
    '71 Opel Kadett 4 Door 36D (2.0 L w/ EFI & Auto) - "Mary Ann"
    '92 Senator B - "Professor"
    '74 Opel Manta - "Barbara"
    '72 Opel GT - "Red Baron"

    In the past owned:
    '04, '05, '06 Pontiac GTO
    2 Bitters (#491/#439)
    '73 Commodore GS
    ATLAS ( 74 Manta w/ 2.8L LK5 )
    & many many other Opels and a even few GTs

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    Just Some Dude in Jersey The Scifi Guy's Avatar
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    As the Grand Poobah of the northeastern branch of the Holy Order of Opel Auto Tranny Lovers, my advice is to leave the auto tranny in the car.

    It's paid for and won't cost you one cent if you leave it alone. It's a more sophisticated device and makes your car way more classy. It's virtually indestructible and almost never needs maintenance. You'll never spill your coffee(or beer) fumbling with levers and dancing your feet back and forth over all your foot pedals. You don't punch your passenger in the knee when you put it in 4th. Stick shifts wear out your engine faster because every bump on the road gets transmitted straight to your pistons and every time you ease off on the gas pedal your piston rings are now your brake pads. Your car is rarer and more special because it's not just another GT with a stick. Auto trannies are much quieter.

    If you want to extend your tranny's range, you can put a 3:18 rear axle in from an early Kadette Wagon, which will drop your highway rpms by 500. It's easier and cheaper to swap a rear than a tranny.

    The far more numerous Holy Order of Opel Auto Tranny Haters may now shoot holes in all my talking points.........


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    Tennessean Site Supporter hrcollinsjr's Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    If you want to extend your tranny's range, you can put a 3:18 rear axle in from an early Kadette Wagon, ...
    Which are getting harder and harder to find.

    Harold

    P.S. I generally prefer manual transmissions but depending on the situation, I can appreciate a good automatic.
    Last edited by hrcollinsjr; 08-23-2013 at 12:01 PM.

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    Opel Tinkerer and Rescuer GoinManta's Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    As the Grand Poobah of the northeastern branch of the Holy Order of Opel Auto Tranny Lovers, my advice is to leave the auto tranny in the car.

    It's paid for and won't cost you one cent if you leave it alone. It's a more sophisticated device and makes your car way more classy. It's virtually indestructible and almost never needs maintenance.
    A good point here Gordo, also notice all those converting from Auto.

    Less than 5% were Autos.. and yet the percentage of survivor (That were automatic) Opel GTs is much much higher than the 5%.

    Its why I will convert my Kadett from automatic to manual, so I can have a good Automatic for my GT.
    CURRENT
    '71 Opel Kadett 4 Door 36D (2.0 L w/ EFI & Auto) - "Mary Ann"
    '92 Senator B - "Professor"
    '74 Opel Manta - "Barbara"
    '72 Opel GT - "Red Baron"

    In the past owned:
    '04, '05, '06 Pontiac GTO
    2 Bitters (#491/#439)
    '73 Commodore GS
    ATLAS ( 74 Manta w/ 2.8L LK5 )
    & many many other Opels and a even few GTs

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    Opel Tinkerer and Rescuer GoinManta's Avatar
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    Quote Originally Posted by hrcollinsjr View Post
    Which are getting harder and harder to find.

    Harold

    P.S. I generally prefer manual transmissions but depending on the situation, I can appreciate a good automatic.
    If anyone knows where I can get a 3.18 that would be swell.

    And I think the 4L60E in my GTO is fantastic. Its also the tranny in Atlas.. doesnt rob any power (GTO is actually faster with the Auto than the Manual 6 speed), and gas mileage is only mildly affected.
    CURRENT
    '71 Opel Kadett 4 Door 36D (2.0 L w/ EFI & Auto) - "Mary Ann"
    '92 Senator B - "Professor"
    '74 Opel Manta - "Barbara"
    '72 Opel GT - "Red Baron"

    In the past owned:
    '04, '05, '06 Pontiac GTO
    2 Bitters (#491/#439)
    '73 Commodore GS
    ATLAS ( 74 Manta w/ 2.8L LK5 )
    & many many other Opels and a even few GTs

  18. #16
    Senior Member Betzjen's Avatar
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    I wish mine was an auto. My knee swells up every time I push the clutch In. And the driving and shifting shifting and shifting is a pain in the butt. I'll swap you my car for your car.??

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    The number of automatics originally installed in GT's exceeded 5% as they are nearer 15% of surviving vehicles despite being junked in greater numbers years ago. They are heavier and run hotter than the standard trans and the box cannot be used in other Opel models because the shifter linkage is reversed.

    A 3.18 will make an Opel a dog off the line unless it has an upgraded engine.

    Getting a smoother clutch can be as simple as replacing its maintenance parts and checking the clutch arm for wear.

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    Opel Tinkerer and Rescuer GoinManta's Avatar
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    Quote Originally Posted by Anonymous D View Post
    The number of automatics originally installed in GT's exceeded 5% as they are nearer 15% of surviving vehicles despite being junked in greater numbers years ago. They are heavier and run hotter than the standard trans and the box cannot be used in other Opel models because the shifter linkage is reversed.

    A 3.18 will make an Opel a dog off the line unless it has an upgraded engine.

    Getting a smoother clutch can be as simple as replacing its maintenance parts and checking the clutch arm for wear.
    I will admit I was going off memory on the 5%.. but as far as survivors.. In temperate climates I don't think the Auto ran much hotter, and less maintenance and a bullet proof transmission I think would have had them survive more not less.

    At least thats my observations at the shows around here.

    As for a dog with the 3.18 if I stick with my Auto in the Kadett, I have to go with it. Due to the high revs of the automatic. But I do have a built 2.0L so its not as big a problem.
    CURRENT
    '71 Opel Kadett 4 Door 36D (2.0 L w/ EFI & Auto) - "Mary Ann"
    '92 Senator B - "Professor"
    '74 Opel Manta - "Barbara"
    '72 Opel GT - "Red Baron"

    In the past owned:
    '04, '05, '06 Pontiac GTO
    2 Bitters (#491/#439)
    '73 Commodore GS
    ATLAS ( 74 Manta w/ 2.8L LK5 )
    & many many other Opels and a even few GTs

  21. #19
    Just Some Dude in Jersey The Scifi Guy's Avatar
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    Yup, my 2.0 with an auto and a 3:18 spins tires at the drop of a hat.

    It's been my observation here on the website that most barn finds of GT's with engines that are still usable are autos and those barn finds with sticks have engines that are toast. I attribute it to the gentler nature of the auto trannies on engines, but it's also likely that the ones with sticks had the heck beat out of them because sticks encourage you to drive like a ninny with your engine at 5000rpm all the time.



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    Auto trans have throttle linkage which is restricted by a lever spring, while manual trans linkage is direct drive.

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