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Hardcore wheelers only-?on using Allison torque converter in turbo 400

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Flipper, Oct 26, 2000.

  1. Flipper

    Flipper Registered Member

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    For hardcore wheelers with good tranny links or firsthand knowledge of turbo 400s-
    Need info on using Allison brand converter for turbo 400(stronger with more torque multiplication)
    It may be the one used in school buses and motor home chassy(model 475 turbo hydramatic-not the 425 which is the old front wheel drive turbo 400 aka 69 Buick Riviera
     
  2. ken

    ken 1/2 ton status

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    Yes, I am using an Allison converter in my crewcab dually 4x4's TH400. Had to after the factory one grenaded itself and destroyed the trans. Allisons as you probably know, are fully braised inside and are fairly well bulletproof. I am using the higher stall (1700 RPM) version. I also have an Allison ready to go into my 77 one ton Suburban 4x4, along with a tricked out TH400...just gotta find time. Anyways, the Allison is THE WAY to go in terms of converters.

    ken
     
  3. ken

    ken 1/2 ton status

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    Oh BTW, Allisons are pricey, mine was $250 from the tranny rebuilder. Maybe one could find it cheaper, I dunno. However, I'll never use a stock (non-Allison) converter again!

    ken
     
  4. Brians 60s

    Brians 60s 1/2 ton status

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    Ken,
    Do you have straight cut planets in your turbo 400s

    "IF YOU'VE NEVER BEEN STUCK.....YOU'VE NEVER BEEN WHEELIN"!!!
     
  5. realsquash

    realsquash 1/2 ton status

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    It sounds like you want a lower-than-stock stall ratio, no? There was a converter used on the deisels with the TH475 (and the th400, IIRC) that was a few hundred RPM lower than the stock gas one, and I seem to think it was an Allison brand. Maybe check out the diesel-page for more info.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  6. ken

    ken 1/2 ton status

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    Well, when I had a choice of Allisons, there were two stalls 1200 RPM and 1700 RPMs (or thereabouts, can't remember exactly). Since the one going into my Suburban is going behind a 454 with a bit of a cam in it, I wanted the motor to be able to get up a bit in RPMs before stalling out the converter. And 1700 is not all that much anyways. I was aware not to have the stall speed above crusiing speed, and I figure with the 39.5" tires and 4.56 gears that I'm cruising the freeway at 2500+ RPM or so (at these So Cal freeway speeds!). As to the diesel being a lower stall, yes I think that makes sense, cause a diesel doesn't need to turn RPMs to make its torque, and actually they don't redline too high (3,000 or so max!). So for a diesel application, I would use the lowest stall I could find.

    Brian, as for straight cut planets, I dunno!! I trust my tranny builder, and when I told him what I was doing with the TH400 in my dually (which is 7400 pounds by itself, then adding a 3,000 pound Lance cabover camper, then towing an 8,500 pound barge, with 5.13 gears and 42" tires) he built it and gave me a warranty. Maybe it does, maybe it doesn't have straight cut. What are the advantages?? (Strength enters my mind).

    ken
     
  7. realsquash

    realsquash 1/2 ton status

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    The straight-cut gears were found in the TH475 stock, but can be used in the TH400 for a lot of extras strength. It's all in the way the gears load each other that makes them stronger.

    On the converter, some hard-core rockcrawler guys use a lower stall converter (ie diesel) so they have better control over their low-speed. I thought the stock speed was around 1700 rpm for gas, but i could be wrong.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  8. Brians 60s

    Brians 60s 1/2 ton status

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    Ken,
    Your a brave sole for having a camper on top of a rig
    with 42s

    "IF YOU'VE NEVER BEEN STUCK.....YOU'VE NEVER BEEN WHEELIN"!!!
     
  9. Brians 60s

    Brians 60s 1/2 ton status

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    Ken,
    Forgot to mention the best way to tell if you have straight cut planets is that you will hear a gear whine
    in first and second gear.

    "IF YOU'VE NEVER BEEN STUCK.....YOU'VE NEVER BEEN WHEELIN"!!!
     
  10. Truckfan2

    Truckfan2 1/2 ton status

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    My dad works at an RV dealership and got a TH400 out of a motorhome with a 454. My question is would it have the allison T/C and straight cut gears? Is there any way to tell beside tranny codes? Oh yeah, ostensibly, it's from a 2wd... can I put a shorter shaft in and use it with an np205?

    Have been stuck (once) as of 8/12/00
    "(2H) Where's all the mud?.(4H)...(4L)..(4H)... oh crap"
     

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