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6.2L backed by an allison 5 or 6 speed

Discussion in 'The Garage' started by K5dreamer, Mar 4, 2007.

  1. K5dreamer

    K5dreamer 1/2 ton status

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    anyone seen this done or heard about it? just a random "sittin on the porch drinkin beer lookin at the truck" moment. im one of the probable few that loves my 6.2L, but id LOVE to ditch the three speed TH400 in favor of an allison 5 or 6 speed. overkill i know, but meh.

    Also does anyone know what t-case comes factory behind those trannies? im sure if i spend a little time online i can find out, but figured id ask and save some time in case someone already knew.

    this is more of a cuiriosity question rather than a "im planning on doing this" question.
     
  2. sled_dog

    sled_dog 1 ton status

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    If you think a Th400 has a lot of parasitic drag, think about that huge old allison. I'd bet you'd need a body lift to fit it... Now a 4l80E sounds like a real world solution to your TH400 problem. Same 1st through 3rd, but with the magic 4th gear. Just a standalone computer standing between you and it, ha.
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I stuck an NV4500 5 speed behind my 6.2... probably a more "real world" solution if you're looking for a bgeefy OD tranny. No computers involved either. :smile1:

    rene
     
  4. K5dreamer

    K5dreamer 1/2 ton status

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    have i mentioned how much i love this forum :bow:

    ive got a 700R4 layin around, but it wont work cuz its from a camaro and from what ive been told it wont match up for a truck application. however i do know the transmision tech at the local chevy dealership. i figure if i give him the old 700 and the trucks current th400, i might be able to work a pretty good deal on a built replacement tranny, whatever it may be. the 4l80e is a good tranny..but i think imma have to do some research on that NV4500 cuz i like the idea of fewer computers. was the NV4500 used in GM applications?

    how much of a pain in the booty was that swap rusty? what kinda tag along problems would i be lookin at? transfer case options, drivetrain angle problems, mounting problems, yadda yadda. im lookin at running a 4in suspension lift at some point, do ya think that would make it harder or easier to do that swap?
     
  5. muddybuddy

    muddybuddy 3/4 ton status

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    i too love the 6.2, im going to be swapping in a 4L80E to get overdrive, should handle it nicely :)
     
  6. K5dreamer

    K5dreamer 1/2 ton status

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    BLAST!! now i know why the NV4500 dosnt have a computer, its a manual. as cool as that is, i dunno if i wanna fool with installing the clutch linkage and all that mess. :rolleyes:
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I swapped from a SM 465 4 speed to the NV4500 5 speed so a lot of things were already in place...like clutch pedal, flywheel etc etc.

    My NV4500 was from a 95 GM 4x4 with diesel. They came with NP241's and other chain drive T-cases and are 32 spline output. The 208 does bolt right up behind them. The problem is they aren't easy to find, and they aren't cheap when you do find them...plus you'll need an aftermerket bellhousing.

    [​IMG]

    I got the tranny as a basket case...here is a pic of it all torn down, case cleaned and ready to re-assemble.

    [​IMG]

    Rene
     
  8. NEK5

    NEK5 3/4 ton status Premium Member

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    Nice work Rene...I wonder how hard it would be to put one in my rig....Colby did it to his, didn`t he? Would 4.56`s still work with the nv4500 and 35s, like they would with the 700r4, being that both have OD?
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Colby got my old 465/205 and swapped it into his Blazer. Yes, the OD and rpm's would be almost identical to the 700R-4. The NV4500 has a .73:1 overdrive, the 700R-4 has a .70:1 OD. Less parasitic loss through a NV4500 though.

    4.56's and 35's at 70 mph with the NV4500 would be 2230 rpm. Same speed with 700R-4 would be 2150 rpm.

    Rene
     
  10. NEK5

    NEK5 3/4 ton status Premium Member

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    hmm...I`d love a standard, but it looks like alot of work..and I already have a nice built 700 waiting to go in.....Dreamers will be dreamers:rolleyes:
     
  11. sled_dog

    sled_dog 1 ton status

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    in a perfect world. I'd bet a 700R4 a little closer to the NV4500 in real world, figure on some torque converter slippage.
     
  12. protechk5

    protechk5 1/2 ton status

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    Ha i just did a manual swap (465/205) replacing my th400/208. Everything I used was off a 79, tranny, tcase, pedal and linkage. Got flywheel, clutch, and pressure plate off a 6.5. It was real easy nothing hard at all, Im having trouble adjusting the mechanical linkage, but if I would had went hydro, it would had been 10x easier. If you can swap a auto tranny in, you can swap a manual tranny and pedal/linkage in.
     
  13. K5dreamer

    K5dreamer 1/2 ton status

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    i agree, the swap is very doable, but right now the truck is my daily driver, because the camaro is getting a complete new interior, 9 speaker sound system with two amps, all associated wiring, and im going to be tearing apart the front end to change the oil pan gasket, and at some point, ive got a 350 block and vortec heads that are going to be built into a 302 small block with a bad attitude. so with the truck, if i did a swap, id just want to do a pull and install change rather than a complete drivetrain rebuild. one major project at a time ;)

    as for the slippage with the 700R4..... did the truck versions not get lockup converters?
     
  14. sled_dog

    sled_dog 1 ton status

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    302 sounds like a sweet project. I have always wanted to build one.

    Yes 700R4 got lockup converters, just saying that they aren't always 100% and especially not in old trucks.
     
  15. K5dreamer

    K5dreamer 1/2 ton status

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    yeah the 302 is going to be sweet, but a bit of a pain in the tucas. the block and heads are from an R code 350, the crank will be from an L99 4.3L LT1, piston and rod combo will be aftermarket, as yet still in the air probly 6in rods and small lightweight pistons. intake setup will be an accel super ram, exhaust will be large tube shorty headers into a 3in exhaust. and camshaft will be a custom grind with the same paper specs of an original 30/30 cam but with modern roller cam profiles for better performance. heads are going to be hogged out for 2.02/1.60 milodon megaflo valves, and pocket ported. im hoping for around 450hp and a 8000 rpm redline :)

    oh and good point with an old worn out lockup, time for a new torque converter :)
     
  16. atho

    atho 1/2 ton status

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    For your original question, the only transfer case that was ever married to an Allison was whatever is under the new HD trucks...and they're driver drop. Other than that, the Allisons were used in heavy trucks in a 2wd configuration...if it was under a med. duty 4x4, it'd have a divorced t-case.
     
  17. K5dreamer

    K5dreamer 1/2 ton status

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    hmm.... heres a thought, the newer GM 6L50-E transmissions. they are available in an AWD setup, but its a longetudinal tranny, which would require a transfer case right?

    they are rated for 332 ft lbs of torque, so my stock 6.2L would be well within the safty limits. and they are rated to a GVWR of 5000 lbs which is well above my K5. and on top of that, it has some rather attractive gearing, except that massive 1st to 2nd drop...

    1 - 4.06
    2 - 2.37
    3 - 1.55
    4 - 1.16
    5 - 0.85
    6 - 0.67
    R - 3.20
    assuming that a decent t-case could be mated up to this thing, even a chain driven case wouldnt be that bad for the power levels im lookin at. although a NP205 would be preferred ;)

    be interesting to see if one of these could be put in as easily as a 4l80-E with just a stand alone computer or something.

    maybe im just being a bit to much of a dreamer for wanting a 6 speed behind my 6.2L :(
     
  18. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Not neccessarely, if he used a 1000 out of the new HD's it has a lock up converter.


    As far as the swap, I have thought about just putting the whole Dmax/Allison setup in my K30. The problem is I don't know of a passenger side Tcase that would work with the Allison.
     
  19. USAJon

    USAJon 1/2 ton status

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    they sell 700r4's thats handle 600+H.P. pricey too!
     
  20. NEK5

    NEK5 3/4 ton status Premium Member

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    Yep, got one sitting in the shed:crazy:
     

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