TH400...is it ruined? Need opinions.

Discussion in 'GM Powertrain' started by Big6ft6, May 9, 2008.

  1. Big6ft6

    Big6ft6 Rockstar 100 Posts

    So last few times I've taken my truck out, when I start from cold...I put into gear and the trans doesn't engage right away. After a few seconds she hooks up, then no problems, shifts are quick and crisp even from stop for the remainder of driving.

    So I've been checking my trans fluid, and adding it when it seemed low..but I'm always nervous about over filling and so often it is hard to see on the dipstick. T

    The other day, my brother noticed as I was putting in more trans fuild, there was a puddle forming under the truck.

    I immediately shut of the truck and checked the leak....cooler lines are rusted and leaking!! So I've parked the truck and ordered some nice new ss pre-bent lines.

    So what are the chances I've ruined the transmission?? I know it is impossible to know for sure..but I planned on putting in a younger engine this summer...if people are sure the trans is ruined..I might investigate finding a younger trans to put in when I've got the engine out.

    I've probably driven the truck 3-4 times since I noticed the initial hesitation to engage and have been adding fluid. One of those trips was 40+ miles.. the rest much less.

    it is an 89 3/4 ton with 200k+ miles hopefully she is o.k.

    Opinions?
     
  2. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    I'm thinking it's probably ok after you replace the lines. An auto transmission relies on transmission fluid to do everything, but unless you ran it for a long time, and ran it hard it shouldn't have caused sever damage. The clutches may have slightly less life left in them, but it should be ok. Mind you, this is coming from another relative newbie to automatic transmission servicing who has moderately severe problems with his transmission (check my thread out for that saga...)
     
  3. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    If the lines were leaking theres a good chance the pump was just cavitating (sucking in air bubbles). when the lines are replaced it should stop.
    Cavitating wont cause issues unless it cavitates excessively and cooks pump parts. If the truck still runs this more than likely didnt happen.
     
  4. Big6ft6

    Big6ft6 Rockstar 100 Posts

    Thanks guys for the opinions! Hopefully I'm alright.

    The new cooler lines are in, and the fluid is topped off. I'm still sometimes getting that initial hesitation when I first put the trans into "D" when the transmission is cold. But once I'm moving there appears to be no hesitation or slipping once the trans engages that first time and I leave my driveway.

    Is a delay when you first put your cold trans into drive a common thing? Should I be worred? anyone else experience that?
     

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