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Tranny rebuild help needed

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blue85, Aug 4, 2000.

  1. Blue85

    Blue85 Troll Premium Member

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    Location:
    Grand Rapids area
    Just did a full rebuild on my 700 tranny (Yes, I know, I must be a masochist) after the torque converter sent metal throughout the tranny and tore up the pump. Almost to my surprise, the truck goes right into gear and drives again. As it turns out, whoever did the engine swap put a non-ECM 350 in place of a computerized 305. Either they didn't bother to make provisions for torque converter lock-up or something just didn't work. I never had lock up and that is probably why the converter puked. I was able to apply power to the lock-up line on the tranny while driving and it locked right up, so I know that the problem is electrical and outside the transmission (thank God). I am confident that I can fix this problem, but my real trouble is elsewhere.

    I have no 4th gear now. The 1-2 and 2-3 shifts are almost normal and the kickdown works fine, plus reverse works fine, so I know that all of the clutches and the 2-4 band are working OK. Therefore, I assume that the lack of overdrive problem is elsewhere. Does anyone have any experience or thoughts on this matter? If I'm gonna run a 700, I might as well save some gas money. Any help is appreciated.

    85 pretending to be a 90
    350 swapped in for stock 305
    5" of suspension lift 33/12.5/16.5
     
  2. River

    River 1/2 ton status

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    Location:
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    I also did a full rebuild off my `89 Th700r4 whit A kit from B&M.
    The problem for not shifting in four gear sounds like you have misplaced a steel ball or wrong setting off the TV cable.
    go to www.BMracing.com then go to the download section and download the TH700R4 transpak the one 565kb. on the last page is a trouble suiting guide and they have also diagrams for the steel balls.
    I hope this will help you.

    Greetings from Amsterdam,

    River `89 K5, 350, TH700R4, NP241, "33, 2.73, 10 bolt F, 12 Bolt R
     
  3. Blue85

    Blue85 Troll Premium Member

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    Thanks for the input, River.

    As it turns out, it was a sticking valve, assumedly the 3-4 shift valve. I pulled the valve body back out on Saturday morning and checked it. It was moving, but not very smoothly. I removed each of the valves that I hadn't removed before and cleaned it all very thouroughly. After this it worked great. I also got the lock-up to work by correcting the wiring problem.

    When the torque converter is locked, a vacuum switch is activated on the engine. Does anyone know what effect this has on engine operation?

    This B&M Super TransKit will give a squeak from the tires on the 2-1 downshift and hold the 1-2 upshift until 5000rpm. I'm really happy with the way the transmission is working now.

    River, BTW: In your tag, is that supposed to say 2.73 or 3.73 gears?

    85 pretending to be a 90
    350 swapped in for stock 305
    5" of suspension lift 33/12.5/16.5
     
  4. River

    River 1/2 ton status

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    Dear Blue85,

    It`s 2.73 and i know this is not a very good setup but as soon as i can find the time i`m going to replace it for 3.73 whit limeted slip front and a detroit locker in the rear.

    And when it`s right than the lockup doesn`t control the vacuum switch but the vacuum switch controls the lockup. This means your lockup converter is controled by engine vacuum.

    I have a question for you to, i rebuild my TH700R4 with the same parts from B&M as you did but when it shifts from 2 to 3 it`s like their is some delay it does this only when i`m accelerating hard like when you hold the clutch for 1/2 second. Do you have the same "problem"?

    Greetings from Amsterdam,


    River `89 K5, 350, TH700R4, NP241, "33, 2.73, 10 bolt F, 12 Bolt R
     

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