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Thread: standard vs reverse gears

  1. #1
    Registered mikibbee's Avatar
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    Question standard vs reverse gears

    i have stock d30/35 axels and wanted to switch out to lower gears but when you buy the gears they ask you standard or reverse rotation

    i dont want low gears on my car that work backwards (drive in first backwards into the garage door)

    how do you tell which rotation you have.
    Radiator Doctor drives:
    91 yj 4.0 liter K&Ned,AX-15,NP231,pacesetter headers, 2 BDS, 2 inch shackle lift, Dana 30 with possy, stock 35. 1 good coat of mud, 1 lack of a muffler, quick disconects front sway bars.

    take two jeeps wheelin and call me in the morning.

  2. #2

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    Quote Originally Posted by mikibbee View Post
    i have stock d30/35 axels and wanted to switch out to lower gears but when you buy the gears they ask you standard or reverse rotation

    i dont want low gears on my car that work backwards (drive in first backwards into the garage door)

    how do you tell which rotation you have.
    All YJs with possibly the exception of some late '95 models that used TJ parts will have reverse-cut D30/35s.
    Horseshoe Bay, BC

    '94 YJ Sahara
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    Quote Originally Posted by seatosky View Post
    All YJs with possibly the exception of some late '95 models that used TJ parts will have reverse-cut D30/35s.
    Nope, that's not correct.

    All YJ's sold in the US came with a HPD30 (high pinion Dana 30) front axle which takes reverse cut (not reverse rotation) gears. Key here is the reverse cut.

    Of these same model year YJ's sold in the US came with a standard rotation D35 rear axle, and some of those are D35C's (the "C" stands for custom, not c-clip even though those same D35C's do have c-clips).

    The reverse rotation gears are not compatable, and can not be installed together in a LPD30 (low pinion Dana 30), and the same goes for the low pinion standard cut gears, those can not be installed in a high pinion axle.

    Sure, you might be able to install a reverse cut pinion gear in a standard cut housing, but the ring gear would not work & vice versa.

  4. #4

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    Quote Originally Posted by Joe Dillard View Post
    Nope, that's not correct.

    All YJ's sold in the US came with a HPD30 (high pinion Dana 30) front axle which takes reverse cut (not reverse rotation) gears. Key here is the reverse cut.

    Of these same model year YJ's sold in the US came with a standard rotation D35 rear axle, and some of those are D35C's (the "C" stands for custom, not c-clip even though those same D35C's do have c-clips).

    The reverse rotation gears are not compatable, and can not be installed together in a LPD30 (low pinion Dana 30), and the same goes for the low pinion standard cut gears, those can not be installed in a high pinion axle.

    Sure, you might be able to install a reverse cut pinion gear in a standard cut housing, but the ring gear would not work & vice versa.
    Ahh, I stand corrected.. I got confused between reverse cut and reverse rotation...
    Horseshoe Bay, BC

    '94 YJ Sahara
    Topless - if it ever stops raining...

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    Quote Originally Posted by seatosky View Post
    Ahh, I stand corrected.. I got confused between reverse cut and reverse rotation...
    IMO, reverse rotation is a bad term to use. The gears for a standard cut vs a reverse cut still spin in the same direction, so there is no reverse rotation business going on.

    It's a matter of where the pinion gear enters the differential housing in relation to centerline with the axle tube or housing that makes the housing fit either reverse cut, or standard cut gears.

    If the pinion lies or enters below centerline of the differential (or below the center of the axle tubes) it will use standard cut gears.

    If the pinion enters above centerline, it will use reverse cut gears.

    The driveshaft, whether it be front or rear, still spins in the same direction as usual/before. That's one reason why I don't agree with the term "reverse rotation" gears. It's just that the load placed upon the gearset will be different.

    That's why a standard cut gear works so well for a rear differential, and a reverse cut gear works (is stronger, if all other factors are equal) in a front differential application.

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    Quote Originally Posted by Joe Dillard View Post
    If the pinion lies or enters below centerline of the differential (or below the center of the axle tubes) it will use standard cut gears.

    If the pinion enters above centerline, it will use reverse cut gears.
    Nice! I had a much more elaborate and confusing version of that going on in my head. This version is nicer on my brain cells.


    Speaking of reverse rotation... can you reverse the rotation of D30/D35/8.8 stuff? I do like my reverse-rotation pontiac engines but I've never attempted to install one in a Jeep. I'd imagine you'd just have to flip the carrier upside-down but I don't know how that would affect the pinion seal setup since it would be reversing the direction of thrust on it.

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    My understanding of flipping the housing upside down from it's normal configuration is a bad approach for lots of reasons.

    The oil that's slung as the ring gear rotates is not sufficiant due to lack of bath size (among other things) with it flipped, and the pinion gear & bearings will suffer from this.

    Axle breather is now on the bottom. Easy enough fix there though.

    Castor for the front will be all messed up unless the inner C's are moved/rotated.

    Steering linkage will be an issue due to the knuckle differences being flipped from side to side.

    Now the tcase output is on the wrong side for the front differential.

    There's are more items I can think of, but this ought to be enough reasons to not want to do just the front.

    I'm not saying it can't be done. Throw enough $ at almost any project & you can make it work. It just doesn't make much sense in this case is my opinion.

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    Can't you flip the carrier over inside the housing to get it to reverse direction? Oh, maybe that's where reverse cut gears would come into play. It's hard to imagine all this stuff without having one in front of me.

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    Quote Originally Posted by Shadly1 View Post
    Can't you flip the carrier over inside the housing to get it to reverse direction? Oh, maybe that's where reverse cut gears would come into play. It's hard to imagine all this stuff without having one in front of me.
    Naw, the carrier has nothing to do with it, plus the housing does not have room to do that with the gears inplace. You can use the same carrier for reverse cut or standard cut ring & pinion gears.

    This pic should help clarify what I'm saying:



    Here's what's key:

    The top/first pic below is of a friends LPD30 w/3.73 gears and a Detroit. Notice the manner the ring gear is cut and that you can barely see the pinion gear below the Detroit & towards the right side bearing cap.

    The second/bottom pic is of a HPD30 w/3.73 gears & Detroit.

    We were swapping in a HPD30 into my friends TJ along with a Warn Hub conversion, Warn inners and Currie steering.


  10. #10
    Registered mikibbee's Avatar
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    wo wo wo please talk slow,
    so if i have a 91 wrangler with the stock axels what gears should i get.
    Standard versus reverse rotation,
    standard versus reverse cut,
    please help me

    thanks a bunch
    Radiator Doctor drives:
    91 yj 4.0 liter K&Ned,AX-15,NP231,pacesetter headers, 2 BDS, 2 inch shackle lift, Dana 30 with possy, stock 35. 1 good coat of mud, 1 lack of a muffler, quick disconects front sway bars.

    take two jeeps wheelin and call me in the morning.

  11. #11
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    Quote Originally Posted by mikibbee View Post
    wo wo wo please talk slow,
    so if i have a 91 wrangler with the stock axels what gears should i get.
    Standard versus reverse rotation,
    standard versus reverse cut,
    please help me

    thanks a bunch
    You have a high pinion Dana 30 (HPD30) front axle, so it's required to have reverse cut gears.

    You have a low pinion D35C rear axle with standard cut gears.

    Do as you wish, but I will never recommend tossing even 1 dime into a D35 rear axle. You have been warned. :idmo: IMHO, it's a ticking time bomb.

  12. #12

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    Its refreshing to read a post by someone who knows what he is talking about so much of what i read on this and other forums is just plain wrong.

  13. #13
    Registered mikibbee's Avatar
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    thank you guys so much
    some times someone has to just say it. (with a warning)
    thanks
    Radiator Doctor drives:
    91 yj 4.0 liter K&Ned,AX-15,NP231,pacesetter headers, 2 BDS, 2 inch shackle lift, Dana 30 with possy, stock 35. 1 good coat of mud, 1 lack of a muffler, quick disconects front sway bars.

    take two jeeps wheelin and call me in the morning.

  14. #14
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    Not a problem.

    I owned a D35C once myself. Key here is "once".

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    Quote Originally Posted by Joe Dillard View Post
    Not a problem.

    I owned a D35C once myself. Key here is "once".
    yup, I had mine for about a month.
    It takes a village to raise an idiot.

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    Thanks for the explanation!

    Just to get it clear.

    this pic belong to a Std Cut?



    and this one belongs to a Reverse Cut?



    Or I'm wrong?

    Aren't all YJ's and XJ's with Dana30's reverse cut with HPDana housing in the front?

    I'm quite confused here yet. So far, the only thing I know (read somewhere) is that STD Cut it's better for the rear diff and REVERSE Cut it's better for the front diff.

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