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T5 with a 1725 motor

Discussion in 'Modified Alpine' started by Mag0152, Jan 16, 2022.

  1. Bill Blue

    Bill Blue Platinum Level Sponsor

    Jim, assuming the photo on the left is the Aisan, it appears to be more compatible to an adapter. Any data, such as to size of bolt pattern and length of input shaft?
  2. Barry

    Barry Platinum Level Sponsor

    The 3.75:1 1st gear ratio is totally unsuitable for a Series Alpine with a 3.89:1 or 4.22:1 rear axle ratio.

  3. Mag0152

    Mag0152 Donation Time

    Gear Ratios

    ALPINE. T5

    1st. 3.12 3.35
    2nd. 1.99 1.93
    3rd. 1.295 1.29
    4th. 1.0 1.0
    5th. 0.72
  4. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, I think the input shaft is a little longer than the T5. There are Ford and Chevy adapters for it. Most use 3.27 or 3.31 rear with the 3.75 first. The Toyota R154 has better ratios. 3.25, 1.96, 1.31, 1.00, .75
    Last edited: Mar 22, 2022
  5. spmdr

    spmdr Donation Time

    An R154 has BETTER ratios? Better than what?

    What is the best T5 gear ratio set for an Alpine?

    T5s have a mixed bag of possible ratios.

    A T5 is a clear case of "You can have what you want, but you can't have everything"

    ...depending on what you want...or you consider as EVERYTHING...

    All of the T5 ratios (including the R154), except the 2.95,

    have a wider RPM drop from 1st to 2nd gear than the stock Alpine trans.

    And the Alpine trans has a Painfully wide 1st to 2nd RPM drop, from a performance view.

    But, a 2.95 T5 has a wider 3rd to 4th RPM drop (than a SV trans, or R154).

    The 2.95 T5 with a .80 5th gear gives a progressive gear ratio drop.

    However, IF you want close ratio upper gears, a T5 with a 1.29 3rd and .083 5th gives a great

    couple of close ratio gears ( closer than the R154).

    So with a T5, you get to chose ratios, most likely more than any other production trans!

    Last edited: Mar 22, 2022
  6. Bill Blue

    Bill Blue Platinum Level Sponsor

    Not ideal, but definitely okay, maybe suitable. I lived with a 3.76 first gear matched with a 3.80 rear in the Durapine for many miles. Many, many drivers took a spin behind the wheel. My only restrictions were I ride shotgun and they tell me their impressions and especially, complaints as they happen. Over the years, this lead to many improvements. But to the point, not one mentioned the transmission, other than "short throw". Perhaps mine was not not a Series Alpine from a technical standpoint, but vastly increased power should have magnified this particular "problem".

    I came to the conclusion that overall low gear ratio was not important if the gearbox had good ratio spacing. The important criteria is 5th overall ratio. I'll spend literally seconds in first gear, compared to hours in fifth. So I'll take a 3.75 first gear over a .65 top gear.

  7. 260Alpine

    260Alpine Silver Level Sponsor

    DW, I meant better ratios than the GM Clone MA5/AR5.
  8. Bill Blue

    Bill Blue Platinum Level Sponsor

    Just wondering, if Barry's comment about the 3.75 first gear is held to be valid, what would be a good rear end ratio to use with the .73 fifth gear AR5? .73 combined with a 3.31 yields an overall ratio of 2.41. Pretty tall for a 1725. The 3.89 gives an overall ratio of 2.84, which might work when combined with 165 X 13" tires.
  9. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, stock Solstice sports car with that transmission use 3.73 for turbo and 3.90 for N/A. Colorado pickups use 3.42.
  10. spmdr

    spmdr Donation Time

    If we are fantasizing of other transes, how about an early Miata 6 spd:







    ....could I live with a 3.76 first gear?

    maybe not with a 4.22 rear....:)

    But, You can bet your sweet bippy, if I had one, I'd work on installing it.

    Last edited: Mar 23, 2022
  11. alpine_64

    alpine_64 Donation Time

    Just install a 3.889 ;-)
  12. spmdr

    spmdr Donation Time

    But, not ALL Miata 6 speeds are the same:

    (no OD and what would you do with THAT first gear??)


    2016 and newer Miata 6 spd







  13. Bill Blue

    Bill Blue Platinum Level Sponsor

    How about a Miata five speed?
    Just as good but more plentiful and cheaper. Unless your addicted to an unsatisfactory 1st gear.

    5.087 low gear? Please tell us that is a typo.

  14. husky drvr

    husky drvr Platinum Level Sponsor

    from an article on differences in new 2016 MX5:

    2. The Miata's manual transmission has an unusual 1:1 sixth-gear ratio

    In most modern manual-transmission cars, fifth, sixth, and even seventh gears are overdrive gears, meaning the transmission's output shaft spins faster than the input shaft to lower engine speed and, hopefully, save fuel. In the Miata's 6-speed, top gear has a 1:1 ratio because the lack of a gearing change saves a minute amount of friction, improving highway fuel efficiency. As a result, all of the Miata's gearing has been adjusted to compensate: The final-drive ratio is an unusually tall 2.866:1 (versus 4.1:1 in the outgoing NC Miata) and the first-gear ratio is 5.087:1.

  15. spmdr

    spmdr Donation Time

    The EARLY Miata 6 spd trans has closer gear spacing, than the 5 spd.

    As a matter of fact, the 6 spd has the same gear spacing for 2nd to 3rd and 3rd to 4th

    As the Tiger close ratio Ford toploader has from 1st to 2nd and 2nd to 3rd, and then

    a bit closer then the Tiger 3rd to 4th.

    I guess you don't HAVE to use 1st gear, of the 6 spd....

    BUT, of course, HERE we are contemplating installing the T5...

  16. phyrman

    phyrman SAOCA Secretary Diamond Level Sponsor

    Conversion Components,Ltd in New Zealand makes a conversion kit to put the Toyota box in an Alpine.
    There is a great write up on the TigersEast/Alpines East web site dated 2-4-2016
    The kit sans Toyota box is a bit pricey, but they have done all the work!
    Something to consider.

  17. DanR

    DanR Diamond Level Sponsor

    Bruce, Some of us are well aware of that option. George Coleman did that years ago and is a satisfied customer.

    I think this discussion was started in an attempt to get something a bit more economical.....
    phyrman likes this.

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