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TH400 delayed reverse (after full warm-up)

Discussion in 'The Garage' started by mrk5, Dec 11, 2004.

  1. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    When I put the truck in reverse after just starting it cold there is no problem with reverse engagement, but after it has been driven for any length of time allowing it to fully warm up there is a bad delay.

    This afternoon I was parking it after driving 20miles, and I had to rev the motor to about 1200RPM to get it to move in reverse. No problems with forward gear.

    Any ideas?
    Is there some sort of adjustments, like bands?

    Oh, and I do have a tranny cooler, but no temp gage.
    Thanks
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    TH400's do have bands that can be tightened. I don't know how to do it but I know it can be done.

    Harley
     
  3. diesel4me

    diesel4me 1 ton status Premium Member

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    Is the fluid full?? It could be a seal on one of the clutches is leaking--when the ATF is cold and thicker it will seal better--as it warms up and thins out,it may leak by the seal easier..of course there are a hundred other things that can do it too. I'm investigating the sudden loss of reverse in my TH350,it didnt want to shift into reverse--its like its got 2 neutrals now,I'm trying to borrow a pressure gauge to do a test and see if I can figure out why it lost reverse that way,before I pull the pan..the book says it could be a clogged filter,valves stuck in the valve body,bad modulator,and what I fear most....blown seals on the clutches,or the clutches themselves are fried--I hear no noise at all in reverse,so I'm hoping its a hydralic problem rather than a clutch problem--but with my luck its probably &^%$$...

    When the website changed I lost the post I had about my tranny problem,and Ryoken posted back with some good tips,and then I found my missing service manual--I'm still debating whether to get too far involved with the TH350,since I'm trying to get another truck,do my shopping and everything else at once--and looking at the pictures in the manual--I doubt if I could successfully rebuild one ---looks like the space shuttle in there to me!!!...I'm hoping I can get reverse to work so I can sell the truck or at least let a friend use it around his yard--or I'll have to part it out--I have a good lead on an 89 K30 with a 454-TH400 and plow,so this truck needs to dissapear to help offset buying the 89 if I go for it....Post back if you find out why your tranny is acting up in reverse--I'd like to know why...
     
  4. kennyw

    kennyw N9PHW Premium Member

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    Last time that happed to me I lost all forward gears within a week and had to have the tranny rebuilt. But I was 19 at the time and didnt know the first thing about auto tranny's yet.

    Since then I've leaned towards the SM465, much easier and doesnt require pixy dust to operate properly :wink1:
     
  5. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Actually it's been doing this to some degree for some time. It was just a lot worse yesterday evening.

    I often debate about going to the 465.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    If it were me, I'd probably try some of that tranny fluid that is supposed to "save" the tranny.

    I would suspect a bad seal if it takes more RPM's (pressure) to engage the gear.
     
  7. adamforsythe

    adamforsythe 1/2 ton status

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    My Th350 is doing the same thing and it is a new tranny with new FLUIDS. Plus I lost park a few weeks ago so when I stick it in park it works when it wants to.
    Thanks
    Adam
     

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