Need help with transmission swap
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  1. #1
    Join Date
    Jan 2016
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    Indiana
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    Need help with transmission swap

    I am currently helping my gfs grandpa put a transmission into his 02 Chevy 2500hd 2wd 6.0
    He got a cheap trans off someone online from out of state. While it is a 4l80e I don't know what it came off of. Possibly a sbc? It's a 6 bolt bellhousing while the old one is a 7. I've been told it should work in theory.

    The biggest issue I've found is the old one had a slip yoke on it. The output shaft has splines running all the along it.
    The new one has a bolt on yoke, and the output shaft is splined only halfway with a oring. The fixed yoke is also chamfered on the inside to seal against the oring.
    The old slip yoke on the driveshaft is twice the length of the bolted yoke and is much heavier duty. It also doesn't have a chamfer so it doesn't actually reach the oring.

    Is there an easy solution? Theoretically I could swap the shafts, but that requires both trans completely ripped apart, and that's way more then I've ever done before, and at that point I may as well just rebuild the old one.

    Do they make a heavy duty bolted yoke? Could I take the old one to the machine shop and have it cut chamfered and drilled to bolt on? The driveshaft is 2 piece with a carrier so I'm not sure why there is a slip joint at all.

    No money to get the old one rebuilt at a shop or to go pull one from a junkyard we know will work. I've never rebuilt one and not sure if I want to practice on someone else's...

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  2. #2
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    Jun 2017
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    Re: Need help with transmission swap

    If you've never had an automatic transmission torn down then you have zero business diving into that one, there's som special tools that make it much easier,I'd look for someone that can do the swap for you, or find th correct transmission.
    NRA LIFE MEMBER
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  3. #3
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    Re: Need help with transmission swap

    Quote Originally Posted by CAVEMANN View Post
    If you've never had an automatic transmission torn down then you have zero business diving into that one, there's som special tools that make it much easier,I'd look for someone that can do the swap for you, or find th correct transmission.
    Find someone to swap the shafts or swap in the new trans? How much would be reasonable for swapping the shafts. I live in rural Indiana if that helps for relative labor cost.

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  4. #4
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    Re: Need help with transmission swap

    you should put back a tranny that fits that truck without all the jerking around changing shafts and what not...youll waste more time and problems than paying to get the correct used tranny..

  5. #5
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    Re: Need help with transmission swap

    Quote Originally Posted by Hobbytime View Post
    you should put back a tranny that fits that truck without all the jerking around changing shafts and what not...youll waste more time and problems than paying to get the correct used tranny..
    I 100% agree. However there's no money for a proper transmission but plenty of time to waste. So I get to bash my head in until I decide F*** this and tell him it can't be done. Not quite there yet tho.
    Gonna go to a driveshaft shop in the morning and see if they have some easy magic solution.

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  6. #6
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    Re: Need help with transmission swap

    Quote Originally Posted by Max Zubrenic View Post
    I 100% agree. However there's no money for a proper transmission but plenty of time to waste. So I get to bash my head in until I decide F*** this and tell him it can't be done. Not quite there yet tho.
    Gonna go to a driveshaft shop in the morning and see if they have some easy magic solution.

    Sent from my LG-G710 using Tapatalk
    lol..well if for nothing else than wasted time you have nothing to lose except your mind...

  7. #7
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    Dec 2008
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    Lockhart,Tx (BBQ capitol of the world)
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    Re: Need help with transmission swap

    The driveshaft shop will be able to swap yokes on your drive shaft to mate to the new trans.
    They can also tell you what measurements to make where. Pay close attention to them!
    Since you have a two piece driveshaft with a carrier bearing there should be no issues with changing the yoke style.

  8. #8
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    Re: Need help with transmission swap

    Not knowing what the tranny came from may present another problem in that it may be from a lighter duty vehicle meaning that it may have fewer clutch plates in the drums to carry the load, honestly, I would find the correct unit, it'll be cheaper in the long run, and not screw the next guy down the road if he tries to replace it by application. Just out of curiosity, what was the old transmission doing, and did you look into having it rebuilt?
    Last edited by CAVEMANN; 02-09-2019 at 03:40 PM.
    NRA LIFE MEMBER
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  9. #9
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    Re: Need help with transmission swap

    Quote Originally Posted by CAVEMANN View Post
    Not knowing what the tranny came from may present another problem in that it may be from a lighter duty vehicle meaning that it may have fewer clutch plates in the drums to carry the load, honestly, I would find the correct unit, it'll be cheaper in the long run, and not screw the next guy down the road if he tries to replace it by application. Just out of curiosity, what was the old transmission doing, and did you look into having it rebuilt?
    Bolted yoke is probably for a heavy duty application. Not sure what might be different inside.

  10. #10
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    Re: Need help with transmission swap

    Quote Originally Posted by CAVEMANN View Post
    Not knowing what the tranny came from may present another problem in that it may be from a lighter duty vehicle meaning that it may have fewer clutch plates in the drums to carry the load, honestly, I would find the correct unit, it'll be cheaper in the long run, and not screw the next guy down the road if he tries to replace it by application. Just out of curiosity, what was the old transmission doing, and did you look into having it rebuilt?
    I believe it just completely stopped working after getting stuck in a field. Fluid was black and burnt. Around here average shop charges 1500 to rebuild them. He got they mystery trans for 150.

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  11. #11
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    Re: Need help with transmission swap

    Im gonna say if he got a 4l80 for 150 its junk or hot or both

  12. #12
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    Re: Need help with transmission swap

    Quote Originally Posted by Ky farmer View Post
    Im gonna say if he got a 4l80 for 150 its junk or hot or both
    I don't even know if you could get a junker parts trans for a buck & a half.
    Max, does it have fluid, smell it, drop the pan look for metal shavings and burnt fluid
    NRA LIFE MEMBER
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  13. #13
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    Re: Need help with transmission swap

    Quote Originally Posted by CAVEMANN View Post
    I don't even know if you could get a junker parts trans for a buck & a half.
    Max, does it have fluid, smell it, drop the pan look for metal shavings and burnt fluid
    Havnt pulled the pan yet, but the fluid out of the torque converter looked good. Not burned or black but definitely not just changed either.

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  14. #14
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    Re: Need help with transmission swap

    Be sure and flush the cooling lines and cooler really, really, REALLY good BEFORE you install the new used transmission.
    All 4L80E transmissions are the same internally. They even share some of the same parts with the TH400.
    Did I say flush the cooler lines and cooler really good already?

    PS, Be sure and flush the cooler lines and cooler really, really, REALLY good!

  15. #15
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    Re: Need help with transmission swap

    Quote Originally Posted by rexcormack View Post
    Be sure and flush the cooling lines and cooler really, really, REALLY good BEFORE you install the new used transmission.
    All 4L80E transmissions are the same internally. They even share some of the same parts with the TH400.
    Did I say flush the cooler lines and cooler really good already?

    PS, Be sure and flush the cooler lines and cooler really, really, REALLY good!
    Any good ways to do that? I was planning on air.
    Also, I think I'm going to make new lines as they connect in different spots and want to keep the stock ones to be able to switch back. I've heard about putting an in line filter on the inlet?

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  16. #16
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    Re: Need help with transmission swap

    Quote Originally Posted by Max Zubrenic View Post
    Any good ways to do that? I was planning on air.
    Also, I think I'm going to make new lines as they connect in different spots and want to keep the stock ones to be able to switch back. I've heard about putting an in line filter on the inlet?

    Sent from my LG-G710 using Tapatalk
    Sounds like you have two different transmissions.
    I don't think I can help you any more.

  17. #17
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    Re: Need help with transmission swap

    The pan should tell something

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    And listen to rexcormack about flushing the remaining system and lines on the target vehicle!!!!! *very important* do not use air!!!(except to blow the solvent) even the flush kits don't really get the coolers cleaned out unfortunately... personally I pump a gallon of solvents though them several times if not actually replacing a cooler.


    If I get a chance I'll find my service manuals on the 4L80's and find the actual differences for you, but usually swapping between models is a labor hungry experiment not for the faint of heart

  18. #18
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    Re: Need help with transmission swap

    Quote Originally Posted by rexcormack View Post
    The driveshaft shop will be able to swap yokes on your drive shaft to mate to the new trans.
    They can also tell you what measurements to make where. Pay close attention to them!
    Since you have a two piece driveshaft with a carrier bearing there should be no issues with changing the yoke style.
    I agree - I've done the same on custom applications.

    But I also agree with those that said get the right tranny.

    It's really the only guaranteed way to go. Swapping them twice sucks.
    Dave J.

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  19. #19
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    Re: Need help with transmission swap

    Quote Originally Posted by rexcormack View Post
    Be sure and flush the cooling lines and cooler really, really, REALLY good BEFORE you install the new used transmission.
    All 4L80E transmissions are the same internally. They even share some of the same parts with the TH400.
    Did I say flush the cooler lines and cooler really good already?

    PS, Be sure and flush the cooler lines and cooler really, really, REALLY good!
    Would it be worthwhile to have a radiator shop flush the cooler?
    Thunderbolt AC/DC
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  20. #20
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    Re: Need help with transmission swap

    Yes! They can flush it aggressively in both directions.
    The independent transmission shop that I use flushes the cooler and lines before they tear down the trans!
    That way it cannot be forgotten!

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