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Trany Hold Back Problem

Discussion in 'The Garage' started by blackrock, Apr 11, 2005.

  1. blackrock

    blackrock Registered Member

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    My TH400 won't hold back when going down hill in 1st gear. I can manually put it in 1st and it will run in 1st gear to climb, but as soon as it out runs 1st gear speed there is no hold back. Iv'e checked the governor and it seems fine. 2nd hold back works fine. Any ideas???
     
  2. 1979jimmy350

    1979jimmy350 1/2 ton status

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    check you vacum modulator it might be bad, you can also get a adjustible one to change your shift points lower or higher. What speed will it hold to it might just be that you are going to fast to hold first with out using manual control. That is why there is the option for manual control for engine braking
     
  3. blackrock

    blackrock Registered Member

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    Thanks for the idea on the vacum modulator. I'll check it out. I can stop at the top of a hill and put it in 1st and let it slowly coast up to speed but the 1st gear hold back won't engage. 2nd gear hold back will catch it at about 30 mph, but that is just too fast on steep hills. It gets real scary on long steep hills when the brakes are the only thing holding back. I'm worried about blowing a brake line and having a runaway. Is there anything else I should check out?
     
  4. 1979jimmy350

    1979jimmy350 1/2 ton status

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    if you have 4x4 you could always put the tcase i low range
     
  5. blackrock

    blackrock Registered Member

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    The tranny won't hold back so low range has no effect since the transfer case is downstream of the transmission. This is a 89 burb with a np 241.
     
  6. 1979jimmy350

    1979jimmy350 1/2 ton status

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    if you put you transfer case in low range it will give you a more efficent engine braking because going down a hill the torque converter is slipping to allow the tranny speed to be greater than the engine speed.
     
  7. blackrock

    blackrock Registered Member

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    I agree, IF the Tranny is engaging. My tranny does not engage. There is absolutly no hold back from the transmission - it completely free wheels so using low range in this case has no effect. I've tried it many times. Using low rangge will back 2nd gear hold back work sooner (slower) but it is still way to fast for a lot of the hils I'm on.
     
  8. 1979jimmy350

    1979jimmy350 1/2 ton status

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    ok i see are you having any problems with slipping in forward gear when you are on flat ground? Possible clutch pack going out?
     

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