T56 tranny selection

Discussion in 'High Tech Retrofits' started by 1st and goal, Mar 20, 2014.

  1. 1st and goal

    1st and goal Veteran Member

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    Hi, I'm looking to convert from my A4 to a T56. Not worried about the install so this is not a "how do I" question.

    As alot of you guys have T56's already I'm looking for advise on which tranny to select.

    Current setup: 98 LS1 motor w/ cam, intake and headers - 370 RWHP / 366 RWTQ. Future intentions are to throw some heads on it but never make too much power (low 400's max).
    I'm looking to buy a new tranny kit and am not sure which direction I want to go.

    Pro touring kit has the following gear sets 2.66, 1.78, 1.30, 1.00, 0.80, 0.63
    Street pro has 2.97, 2.10, 1.46, 1.00, 0.74, 0.50

    Intentions are to drag race and auto X from time to time (couple times a year) but mainly I'm looking to have better driveability / fun and improve mileage. I want to have fun and use the car, it is in good shape but is no trailer queen.

    Currently with my A4 I cruise 75 mph at around 2300-2400 ish (car's in winter storage so I'm going from memory) and if I'm just checking highway mileage I get 19-20 mpg, mixed milage is 14-18 bepending on how much I get on it (which is fairly frequently)
    What rear gears do you you have and what rpm do you cruise at? What kind of mileage do you get?

    Any wisdom is appreciated.
    Thanks Marc
     
  2. 70 gsconvt

    70 gsconvt Veteran Member

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    One piece of advice I'd give is if you're doing it for improved fuel economy, save your money. It'll take you 20 years to break even. Now better cruising down the highway, I understand that. And I like rowing the gears too.

    Tell your wife/girlfriend it'll be better on gas, but don't do it for that reason. I went from a th400 to a 200-4R in my Buick GS. It's great on the highway now with it's 3.73 gears. But mileage only went from about 10 to 12 mpg or so. Two mpg for the $3500 it cost would never make good financial sense.

    You may want to consider just called Rockland Gear. They have very good pricing on the T56's. That's where I'm going to go when I'm finally ready to "get better gas mileage" in mine.
     
  3. 1st and goal

    1st and goal Veteran Member

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    Back when I put the LS1 into the car I was mulling over throwing a big block in there but decided I'd go for the LS1 for overall power, "wow factor" and mileage.....still waiting for my return on investment on that one too :)
    Any increase in mileage will be a bonus, mainly looking for better driveabity and fun, the A4 comes out of the hole great but never been enamoured with the drivability.
     
  4. 1934chevycoupe

    1934chevycoupe Veteran Member

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    i'm at the same point as you, although i have to also pick rear gear ratio at the same time. not sure which way to go.
     
  5. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

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    What rear gear do you have? What's the lowest cruise RPM (loaded, on a slight incline) you think the engine would be happy with?

    I'm not a fan of the way they "crossed up" the ratios in those trans. It used to be that 2.66->0.50 was one trans (the one I have), and 2.97->0.63 was the other (what I would have preferred, actually). Rear end ratio becomes a compromise for the street with the two options they have now.
     
  6. 1st and goal

    1st and goal Veteran Member

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    I'm running 3.42's now, willing to change gears if needed......this is where sometimes I feel like I can answer my own question.....if I'm going to increase to 3.73 or 4.11 then why not just get the tranny with a 0.63 sixth gear and keep the 3.42's? For low rpm cruise I'd say it would be OK in the high teens, if I'm cruising now with the converter locked it does seem ok in the 1700-1800 range, doesn't take long for the converter to unlock and bam I'm in the powerband.
     
  7. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

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    That's my thought. No sense going to higher rear and bumping your driveshaft speed up, never mind the cost. Driveshaft vibrations have been a PITA for a LONG LONG time for me, so don't spin it any faster than you have to, IMO.

    I have a factory '94 unit- 2.66 1st, 0.50 6th, with 3.42s and 26.0" tall tires. I'm about 1500rpm at 65mph. The engine is fine there, I run the ZZ4 cam, so very mild, but overall it would feel better at 1700 at that same MPH.
    With 3.42s, I'd prefer the factory 2.97 1st with 0.63 6th (that trans was $1000 more when I bought mine in '95, since it wasn't on special), but they switched them up in these aftermarket transmissions.

    FWIW I get 24mpg on the highway, cruising at 70-75mph. That's with a QJet, so you can likely do as well, even with more cam.
     
  8. 71RS/SS396

    71RS/SS396 Veteran Member

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    There's actually a 3rd gear set option to confuse you even more 2.29 1.60 1.21 1-1 0.85 0.67 which is what I'm using. Rockland and Bowler Performance are the only 2 places that build the magnum with this gear set to my knowledge.
     
  9. sbca96

    sbca96 Veteran Member

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    2004 GTO 350 hp LS1

    T-56 : 2.97, 2.07, 1.43, 1.00, 0.84, 0.57

    3.46 axle ratio

    255/40R18 tire

    22 mpg combined, 27 mpg highway only, 24.5 mpg mostly highway trip.

    weight 3750 pounds (typo)

    1250 rpm @ 50 mph
    1500 rpm @ 60 mph
    1750 prm @ 70 mph

    Tom
     
    Last edited: Mar 27, 2014
  10. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

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    What?? No way.
     

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