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Thread: B20a G.Box - Adapter Plate project!! Input needed!!

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    Tomisimo's Avatar
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    B20a G.Box - Adapter Plate project!! Input needed!!

    Well like the title says, I'm thinking to develop a B20a8 Gearbox adapter plate to mount B20 gearbox to a A20 engine. In my heat it sudnt be that hard if I have a proper CNC program to machine it.
    I have at the moment aces to a CNC machine that I can use to mill such things.

    But I dont have aces to any B series g.box and my car is like 550mils away at home, so I dont have aces to my spare g.box either.

    I need someone who can take a detailed image of B gearbox with reference in millimeter.. and the A series g.box in details, so I can scathe a drawing and write a program..

    So tall me what you guys think?

    Its prttey fnuny how you can raed tihs eintre snetnece with all tehse ellters out of palce...

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Did you mean that you want to put an A20 transmission on a B20A engine?
    Because the other way around doesnt make much sense to me when the B20A transmissions are so rare compared to A20 trannys.


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  3. #3

    Tomisimo's Avatar
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Quote Originally Posted by thegreatdane View Post
    Did you mean that you want to put an A20 transmission on a B20A engine?
    Because the other way around doesnt make much sense to me when the B20A transmissions are so rare compared to A20 trannys.
    Huh I see.. No I mean B on A engine.. what other options do we have? with good gear ratios and cable clutch? Lude trannys?

    Its prttey fnuny how you can raed tihs eintre snetnece with all tehse ellters out of palce...

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Do you like the B20A trannys gear ratios better than A20 gear ratios?
    The gear ratios are almost the same, take a look:



    I think the A20 trannys have the best gear ratios especially if you get usdm gears, they have some that are longer than our EDM gear ratios.


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    Tomisimo's Avatar
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    hmm i see that the A2K5 have higher top speed.. than a B2K5, those gears you talking about from USDM models, what gears is that?
    The problem is that the B2k is stronger option for boost engine than A2k and I was thinking of putting a LSD in my tranny.. Any options on that?

    Its prttey fnuny how you can raed tihs eintre snetnece with all tehse ellters out of palce...

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    You'd be better off doing a regular B (B16, B18, etc) series transmission, as there are LOTs of options for LSDs, Gears, etc.

    But if you do a B20Ax Gearbox on an A20, the adapter plate should work in reverse as well, shouldn't it? Or would you use some sort of countersunk holes to tuck the bolt heads into?

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    A quick search in forum gave me these ratios for USDM cars (not sure if they are 100% correct):



    Yes you do have the advantage of being able to use a torsen LSD in the B2K5 transmission. I dont know which tranny is stronger though but I think both are strong enough.
    But why not just use the B2K5 tranny on a B20A engine?


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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    main difference between b20 and a20 is the bolt size, a20 use 14mm bolts and b20 use 17mm bolts, I suppose over in norway b20a with manual boxes are everywhere?

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    3Geez Veteran A18A's Avatar
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    would you also need a flywheel spacer and some other kind of flywheel bolts?

  10. #10
    3Geez Veteran MessyHonda's Avatar
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    my plans were use the b18 housing with the integera internals and lsd for the b20.

    1989 Honda Accord LX-i
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Are d-series trannies not a better option? They are incredibly available and pretty strong. Not to mention aftermarket availability.
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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Wow 300km/h on carb gears? it might be in ratio turn but you never get all out of it. Anyhow, the story goes like that.
    I was in contact with Honda INC of Norway with questions about swaping in a B18 or F20b or H22 engine in my 3gee. Because if You want to do any swap in this country you need to go true hell to get something like that street legal, I dont want to end up with a race car that may only be used on a track.
    But since they are skeptical I thoat that I just boosted my A20 to 220-250Hp on wheels and do a g.box swap for LSD reason. I read of ppl that say that boosted A20 is beter than B20, and I can relate to that as the A20 is steel block and B20 is Aluminum block, same story with DSM Mitsubishi, they swap 1G Eclipse steel block in to 2nd or 3rd Geen Eclipse to get more stronger engine.
    Anyways, There are few B20 still available here, but mostly Auto tranny.
    Yes if I ever going to make that plate, it might be used in reverse too, as long as bell housing was taken in measurements, because some curves is a bit different betven those, Dont know if one going to need a spacer but it must be tasted to fit first

    Its prttey fnuny how you can raed tihs eintre snetnece with all tehse ellters out of palce...

    My Build Thread

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Hmmm this is pointless get a 1st gen integra gearbox should be some around your way or in the U.K. failing that just get all the parts from honda for it!! And BTW 99-00 Civic SI LSD from OBX or Quaife fits. The integra parts fit into the Accord bellhousing, i'm running a Accord bell houseing with Teggy gearbox on a 2nd gen prelude 1.8l carbed flywheel lightened to 10lbs and a clutchnet red plate and organic disk this is holding fine at 190bhp with revs upto 7.5k with honda mtf all is well after 3000k miles and before that the gearbox had done 15k miles before that it was rebuilt with new syncros on 3rd and 4th and race spec bearings used on the diff and new seals on everything. When it needs another rebuild I'll be putting the Civic LSD in.

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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    The 99-00 Civic Si B16 differential fits the B20A transmission. I dont think it will work in the A20 tranny.


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    Re: B20a G.Box - Adapter Plate project!! Input needed!!

    Well it does seen a write up on a 3rd gen civic that has a 1st gen Teggy D16ZC box and as thats the same as ours and all he had to do was grind a tiny bit of ally off the inside of the casing it's a done deal.

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