4WD transmission ratios (84-87 vs 89+)

DD Wagonist
in Engine & Drivetrain
In the midst of a rebuild of a '89 RTawd trans.... happened to have both a '87 and a '89 on a table at the same time. Exterior wise, the cases are similar, but different and not interchangeable (different rear trans mount bolt pattern, different but similar gear change assembly, etc).

Anyway, here's the gear ratios and teeth count for both gearsets. If anyone can confirm or dispute any of this info, please post up.

RTawd%20Trans%20Ratios.JPG

I will more than likely end up using the '87 3/4/5 in the '89 trans, since they're only a little longer, and the engagement dogs are in 50x better shape.

D

Comments

  • JL56TCJL56TC New Wagonist
    I've had both and to tell you the truth my 89 is much stronger I finally broke it a 280bhp but there is no way my 87 would have survived that long... although the low end is better on the 87 the mid and high on my 89 is much smother and more efficient in the long run
  • DD Wagonist
    JL56TC wrote:
    I've had both and to tell you the truth my 89 is much stronger I finally broke it a 280bhp but there is no way my 87 would have survived that long... although the low end is better on the 87 the mid and high on my 89 is much smother and more efficient in the long run

    The only size difference i was aware of is the mainshaft (87 and earlier being smaller input spline). gear diameters and surface area are very close if not the same (depending on gear ratio). Only other strength difference could possibly be due to the case design itself, which the differences are pretty minimal. I can't see how the later trans could have a higher torque/load holding capacity.
  • maxDURANDmaxDURAND Band Wagon
    anyone have ration from an s22 hydro
  • JL56TCJL56TC New Wagonist
    D wrote:
    JL56TC wrote:
    I've had both and to tell you the truth my 89 is much stronger I finally broke it a 280bhp but there is no way my 87 would have survived that long... although the low end is better on the 87 the mid and high on my 89 is much smother and more efficient in the long run

    The only size difference i was aware of is the mainshaft (87 and earlier being smaller input spline). gear diameters and surface area are very close if not the same (depending on gear ratio). Only other strength difference could possibly be due to the case design itself, which the differences are pretty minimal. I can't see how the later trans could have a higher torque/load holding capacity.


    actually my output shaft broke on my 89 and the splines on my 88 were striped to hell I had a week clutch on my 88 but there is a major diffrance(I think) in they way they shifted my 88 was pretty rough
  • DD Wagonist
    JL56TC wrote:
    actually my output shaft broke on my 89 and the splines on my 88 were striped to hell I had a week clutch on my 88 but there is a major diffrance(I think) in they way they shifted my 88 was pretty rough

    Just to re-iterate. Transfer bevel gears of the early style case (84-87 4x4 and RT) are interchangeable with the later style case (89+). They are not weaker, they are the same. Period.
  • JL56TCJL56TC New Wagonist
    D wrote:
    JL56TC wrote:
    actually my output shaft broke on my 89 and the splines on my 88 were striped to hell I had a week clutch on my 88 but there is a major difference(I think) in they way they shifted my 88 was pretty rough

    Just to re-iterate. Transfer bevel gears of the early style case (84-87 4x4 and RT) are interchangeable with the later style case (89+). They are not weaker, they are the same. Period.



    clearly not true... if the gears were the same the ratios would be the same ... which there not... according to the HONDA manuals that i have
    so i really dont know what your talking about... they might be interchangable but they are not the same.. period
  • DD Wagonist
    JL56TC wrote:
    clearly not true... if the gears were the same the ratios would be the same ... which there not... according to the HONDA manuals that i have so i really dont know what your talking about... they might be interchangable but they are not the same.. period

    Edit:

    Info provided from jaker: "In the 1988-91 transmission, they are most definitely not 1:1. The drive gear is 21 teeth, and the driven gear is 19 teeth. Here's a couple of pictures showing that."

    476.jpg

    477.jpg

    So, thanks to jaker for the correction.

    And i pulled part #'s from the honda/acura EPC...

    Transfer section bevel gears:
    86 4x4 29210-PH8-010
    87 RT 29210-PH8-961
    88 RT 29210-PH8-900
    89 RT 29210-PH8-900 and 29210-PH8-910

    Transfer bevel gear bearings
    86 9122-PH8-008
    87 9122-PH8-008
    88 9122-PH8-008
    89 9122-PH8-008 AND 91122-PS5-003

    Transfer Shaft
    86 29201-PH8-000
    87 29201-PH8-010
    88 29201-PH8-900
    89 29201-PH8-900

    Transfer shaft collar
    86 29311-PH8-000
    87 29311-PH8-000
    88 29311-PH8-000
    89 29311-PH8-000

    All i have access to currently are 2 early style 84-86 4x4 box's.... i'll pull the transfer section out of them both and confirm. I am curious why the suffix code on the 87RT bevel gears is different from the 86 4x4. Apologies for any misinformation.
  • JL56TCJL56TC New Wagonist
    D wrote:
    JL56TC wrote:
    clearly not true... if the gears were the same the ratios would be the same ... which there not... according to the HONDA manuals that i have so i really dont know what your talking about... they might be interchangable but they are not the same.. period

    Edit:

    Info provided from jaker: "In the 1988-91 transmission, they are most definitely not 1:1. The drive gear is 21 teeth, and the driven gear is 19 teeth. Here's a couple of pictures showing that."

    476.jpg

    477.jpg

    So, thanks to jaker for the correction.

    And i pulled part #'s from the honda/acura EPC...

    Transfer section bevel gears:
    86 4x4 29210-PH8-010
    87 RT 29210-PH8-961
    88 RT 29210-PH8-900
    89 RT 29210-PH8-900 and 29210-PH8-910

    Transfer bevel gear bearings
    86 9122-PH8-008
    87 9122-PH8-008
    88 9122-PH8-008
    89 9122-PH8-008 AND 91122-PS5-003

    Transfer Shaft
    86 29201-PH8-000
    87 29201-PH8-010
    88 29201-PH8-900
    89 29201-PH8-900

    Transfer shaft collar
    86 29311-PH8-000
    87 29311-PH8-000
    88 29311-PH8-000
    89 29311-PH8-000

    All i have access to currently are 2 early style 84-86 4x4 box's.... i'll pull the transfer section out of them both and confirm. I am curious why the suffix code on the 87RT bevel gears is different from the 86 4x4. Apologies for any misinformation.


    understood and agreed
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