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Howd'ja replace O-Ring in a TH350 where the speedometer cable connects?

Discussion in 'The Hokey Ass Message Board' started by bruceg, Apr 12, 2010.

  1. bruceg
    Joined: Jun 1, 2009
    Posts: 52

    bruceg
    Member
    from NWATL

    Sorry for showing that I am clueless. The TH350 in my son's car is leaking like a sieve from where the speedometer cable goes in to the transmission housing. We just parked it and let it leak. That's not cool! So - how do you go about replacing the O ring on a TH350 where the speedometer cable connects? It looks like that is where it is leaking. The motor is a '75 350 (I know, too new for HAMB). The transmission is around the same vintage.

    (go ahead and flame away - I should be able to figure this one out.)
     
  2. Undo the bolt that holds the holddown clamp, pull out the speedometer piece. Replace the O ring. That is the easiest leak to fix.
     
  3. I just fixed the same problem on my TH350. Their is actually an inner seal and an outer o-ring. It is hard do tell from just looking at it from the outside which is the problem. I'm willing to bet it doesn't get bad until it sits for a few days?? What is happening is the torque converter is draining back into the pan and raising the fluid level and now it is leaking. The OEM ones where aluminum and just wear out over time.
    EASY FIX. If you have a decent trans shop near you go in and ask for a "Speedometer Bullet" for a TH350. If you don't have a local place order one from here.

    http://www.transmissionpartsusa.com/TH350_Steel_3_4_Bullet_Speedometer_Housing_p/470-00047338a.htm

    It has the new inner and outer seal in it. Just loosen the locking tab, swing it out og the way pull the old one out and slide in the new one. Please let me know if I can be of any more help. Todd
     
  4. bruceg
    Joined: Jun 1, 2009
    Posts: 52

    bruceg
    Member
    from NWATL

    Thanks, and ordered. (I know, I should get off my lazy hind-end and save the shipping and handling charges!)
     

  5. bruceg
    Joined: Jun 1, 2009
    Posts: 52

    bruceg
    Member
    from NWATL

    Thanks for the info. Installation was a breeze. While under there, I noticed some leaking from the pan gasket. Not all the bolts were torqued to 12 foot pounds. I torqued it, but think I'll sneak out and pick up a new pan gasket for good measure. Might as well, since it's up on jack stands and I already have tranny fluid on the ground! Besides, the car has been parked for a long time, and before we got it, it was parked a good 12 years under a tree. Might be time for a fresh pan gasket.
     
  6. Deuces
    Joined: Nov 3, 2009
    Posts: 21,306

    Deuces
    Member
    from Michigan

    While your at it, also replace the trans filter!! the whole kit with a new pan gasket is about 7 bucks. Well it was the last time I bought one. :)
     
  7. bruceg
    Joined: Jun 1, 2009
    Posts: 52

    bruceg
    Member
    from NWATL

    Will do. It's my middle kid's car, and he's off to seminary for 4 years (well 3 more) and then another 4 years of school. My wife wanted to ditch the car. I figured my other son and I would fix the transmission leaks, get the engine running again (I think it's just the fuel pump, it's not getting any fuel to the carb and we already did the fuel sending unit and sock). If we can get it running, shifting and stopping (we have some brake work to do) - then I'll let it hang out in the garage until my kid graduates or finds what he wants to do. We had it at that point a year ago, then a bunch of stuff broke. Gives me something to do. (other than my car and my camper and ....)
     
  8. Deuces
    Joined: Nov 3, 2009
    Posts: 21,306

    Deuces
    Member
    from Michigan

    I'm not sure how many qts of trans fluid the TH350 holds... Might want to buy 4 qts for starters. Poor at least 3 quarts in before you fire it up then check the fluid level.
     

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