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1991 350TBI, 4l80E, 241case,can it be done?

Discussion in 'The Garage' started by Scott39, Jun 6, 2005.

  1. Scott39

    Scott39 1/2 ton status

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    I have an 91 blazer, 350tbi,700r4,241 case, does anybody know if I can put a 4l80E in my blazer instead of the 700r4?
    Thanks
     
  2. u2slow

    u2slow 1/2 ton status

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    Sure. Get the harness, ECM, 4L80E, and NP241 from a '91 V2500 Burb.
     
  3. muddybuddy

    muddybuddy 3/4 ton status

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    isnt the 4L80E pretty much the same thing as a 700r4?
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Thats the 4l60, 4l80e is bascially a TH400 with an overdrive unit. the 4l60 is still shifted with the TV cable, while a 4l60e and 4l80e are both shifted with a TCU (transmission Control Unit)
     
  5. muddybuddy

    muddybuddy 3/4 ton status

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    thanks for clearing that up :thumb:
     
  6. Scott39

    Scott39 1/2 ton status

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    Can you still put a short shaft kit in this tcase (NP241 from a '91 V2500 Burb).
    I have a new short shaft kit in mine I would like to use.
     
  7. grape

    grape Registered Member

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    I have one behind my 6.5 in my K5. The input gear on the 241/ or 208 in my case, has to change to the 32 spline turbo 400 input gear. the shift linkage needs to be moved back a couple inches and you will also need the the turbo 400/208 or 4l80/241 transfer case adapter, the tall one. The most fun part is purchasing the controller to run the transmission :( , I'm using the PCS version which requires a driven wheel speed sensor to be mounted to the rear pinion yoke.
     
  8. jac6695

    jac6695 1/2 ton status

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    Why not put the extra cash into your TH700 to make it stronger?
     
  9. grape

    grape Registered Member

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    In my case I didn't want the stupid TV cable affecting the amount of travel on my throttle on the injection pump, not to mention we are making almost 550 ft/lbs with my 6.5.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    From what we figured out in another thread, if I've got everything right, to do this with stock parts...

    You'd need the PCM from a 1991 R/V truck with the 4L80E. That PCM number was in that thread. You'd either need to burn your own PROM, or get one that is for a 350 off the bat. A 4L80E of course. Whatever adapter you need, apparently what was posted above. A 241 from a 90-91 truck, but it would have to have been behind a TH400 (1990 I guess) or 4L80E (1991) to get the right splines and VSS off the bat. In the posters case, the right input shaft alone would do the trick.

    Getting all that should be exactly what anyone needs to do the swap. Easier because the poster has TBI, and VSS in the t-case.
     
  11. Scott39

    Scott39 1/2 ton status

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    Only if a tranny shop can build one strong and dependable.
    I like to wheel it hard, but not abuse it, and drive to the trails and back.
    My 700r is making a small ticking noise in 1st & 2nd gear in 4lo when I wheel, but not when I street drive it.
     
  12. Scott39

    Scott39 1/2 ton status

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    Great info, thanks.
    But in your opinion, is it worth the swap, or just have my 700r totally built from a good shop?
    Or if I trade my core in and get a built 4L80E from some shop like bowtie?
     
  13. grape

    grape Registered Member

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    I'd say you could probably be happy with a 700 in a gas application. Nobody on earth seems to be able to make a 700 live behind the diesel if it's anything but stock power. I just got frustrated with all the shops in my area not ever being able to get the shift points right with 3 different 700's, so i said screw it, I'll tune it with a lap top.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    If I was doing this, I'd build the 700 myself and stick with it. Cost would be much less, and I have no one to argue with when/if it fails.

    You hear a LOT of horror stories about the 700, and I'm sure that 99% of them are due to rebuilder error, hurrying up, trying to cut corners. The 700 is "finicky", but as long as you do things right, they can be built strong.

    The 4L80E I don't hear much about rebuilds. Probably because stock, they don't break very often. But you'd have to hear from someone else that deals with trannies every day on what they see with the 4L80E's. I know they are excellent trannies, but as far as digging into them, no clue.

    4L80E comparatively sucks a lot of power up, so thats something to consider as well, but comparing stock to stock, it will take a lot more abuse. It would probably end up being quite a bit cheaper to just dump all your money into a 700 by a place you can trust (or yourself) instead of paying all the costs of a conversion to 4L80E, PLUS the acquisition cost of one of those as well. As long as the 700 build lasts.
     
  15. Kyle89K5

    Kyle89K5 1/2 ton status

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    The situation your are describing WAS a factory option in 3/4 ton Sub's late in their production life. A guy in town has got that exact same setup in his burb (that's wheeled HARD and tow's his blazer)

    It's doable, worth the time and effort? well, that's tough saying. Who's time and who's effort?

    My point was, that it's not only possible, but it's done in vehicles of the same year and bodystyle as yours. Finding a wrecked burb with all those parts would make life a LOT easier :D
     
  16. 74kay5

    74kay5 1/2 ton status

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    I have a 4L80E out of a 91 Suburban I'm considering selling. It was rebuilt by GM goodwrench 2 years ago. My friends suburban was totaled and I bought it off of him 6 months ago. I'm no closer to doing this swap now than I was then so if your interested let me know. If I was you I would get a manual kit for it if possible. Transmission Center sells built non computer 4L80E transmissions.
     

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