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Technical Th350

Discussion in 'The Hokey Ass Message Board' started by WP38, Oct 5, 2017.

  1. WP38
    Joined: Jan 23, 2015
    Posts: 268

    WP38
    Member

    Is there a direct replacement for the th350 transmission? 700R?
    My transmission is in need of repair. Looking at options. I have a Lokar shift floor. Hooked up to a Chevy
    305. Might also be looking at replacing the 305 down the road


    Sent from my iPhone using The H.A.M.B. mobile app
     
  2. EnglishJon
    Joined: Oct 27, 2009
    Posts: 39

    EnglishJon
    Member

    The 200R is the same length and output shaft spline, your drive shaft won't have to be altered. You will have to cut the mount pad off the cross member and weld it to the other side of the cross member, though depending on your application you may find an aftermarket crossmember for this conversion. Also needed are a TV cable and Holley TV cable bracket ( this may need rework for your application) and a lockup converter (input shaft splines are different between the 350 and 200R).
    There is a lot of info on this conversion on the web and will definitely enhance your Hot Rod
     
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  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,269

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    2004R is the better choice vs 700R4 for several reasons. As the above posts points out, the length and outputs line are the same as your TH350. Beyond that is a better ratio spread in the 2004R.....2.74 1st gear vs 3.06 in the 700R4, with essentially the same O/D ratio.

    Some people claim the 2004R is weaker, but that was also true of early 700R4's and both were greatly improved in subsequent production revisions. Any competent rebuilder will use the correct parts for overhaul.

    Ray
     
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  4. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    Another option is to take the TH350 apart, see what's wrong with it, and rebuild it. If it doesn't need any hard parts, it's not that expensive. If it does need hard parts, you'd want to scrounge around for another transmission or two to get parts from.

    My guess is you are not looking to spend a lot of money replacing the transmission...??? if you buy and get a 200-4R rebuilt and upgraded, it will probably cost quite a bit more than having your existing transmission rebuilt.

    As to whether or not you want to spend money to get overdrive...there are a lot of variables that make that either a good idea, or a waste of time/money. Most have to do with how your truck is set up now, and how you drive it.
     
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  5. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 24,653

    Jalopy Joker
    Member

    yep, lots of options out there - up to you - Phoenix Transmission, Weatherford TX has good stuff - with 200r will need to add lower rear gears to list of swap needs
     
  6. If you got a long tail T350 the 700R4 is a bolt in.
     
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  7. X2. Soft parts are probably $200-$300, why not give rebuilding it yourself a shot.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  8. This is what I would do, there is a tool for inserting the pistons but you can rent it for a day.

    Personally I would bite the bullet and replace it with a T-400 but I break 350s. LOL
     
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    if you can't build a Th350 to live behind a 305...hmmm....

    :)
     
  10. LOL I didn't look at what he was running. I always assume that hot rodders are building something that runs. :D
     
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  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,950

    gimpyshotrods
    ALLIANCE MEMBER

    My 305 runs just fine at 250hp. Sends a 2300lb car down the road quite nicely.

    Oh, and I got it for free, and hopped it up with all of $400 in parts.
     
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  12. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    and it probably doesn't need a TH400 behind it....might even get by with one of those little overdrive things.
     
  13. 1, Yes..It's called a T350 C
    2, If you are going to replace the 305 at a later date, to ...(not stated), why not just fix the T350 for now?
    3, Seeing you're asking for advice here, why not tell us what your current rear end ratio is, and how much highway driving you actually do? This way ,we can give you more informed suggestions.
     
  14. blownhemi48
    Joined: Nov 17, 2009
    Posts: 234

    blownhemi48
    Member
    from Bergen NY

    The T350C used a lock up converter which would drop your cruising rpm's down a couple hundred.
     
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    there is also the 250 and the 250C :)

    but we're going backwards here
     
  16. Yeah, but a good source of light weight racing parts;)
     
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  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,950

    gimpyshotrods
    ALLIANCE MEMBER

    Exactly.

    Overdrive transmissions are pretty damn skippy, IF the fuel savings will more than cover the cost to switch to one, along with all of the ancillary parts.

    Often times, it does not.
     
  18. F.O.G
    Joined: Oct 31, 2006
    Posts: 259

    F.O.G
    Member
    from Pacific,Mo

    Don't need a special tool for the clutch pistons, just install new seals and wrap tight with
    electrical tape and put in the freezer for about 6 hrs. Place the center seal in place and slide over a
    tapered glass, like a shot glass, all garages have those. Been doing it that way for 40+ years.
    Contact me if you need more info. Probably something on You Tube about it.
     
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  19. Remember the good old days when you could go to ANY boneyard and get a turbo 350 Trans? They were laying everywhere like goose shit.
     
  20. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    heh...I was visiting a few local street rod friends this week, and I noticed that TH350s are still laying around everywhere. Probably not at the junkyard, but in guys back yards, after they swapped in an OD.
     
  21. Roger O'Dell
    Joined: Jan 21, 2008
    Posts: 1,081

    Roger O'Dell
    Member

  22. zzzzzzzzzzzzzzzzzzzzzzzz
    Now there's a combo ..Stock 305 and a 'glide.
     
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  23. Gregg Pellicer
    Joined: Aug 20, 2004
    Posts: 1,346

    Gregg Pellicer
    Member

    When considering a swap just remember the th350 comes in three different lengths
     
  24. 2.73 rear gears, powerglide and a 305! Yee haw



    "If it ain't broke - fix it till it is"
     
  25. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,950

    gimpyshotrods
    ALLIANCE MEMBER

    0-6 in just 7 seconds!
     
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  26. WP38
    Joined: Jan 23, 2015
    Posts: 268

    WP38
    Member

    This is what I found in the transmission tray with some light gray matalic material.
    I'm thinking at this point to just rebuild it as is,
     

    Attached Files:

  27. squirrel
    Joined: Sep 23, 2004
    Posts: 45,366

    squirrel
    Member

    that's the shift detent spring, you should find the other half of it under a bolt head that holds on the valve body.

    I would not let that scare me too much...I'd just replace it, and see how the trans works

    TH350HPfilter.jpg
     
  28. WP38
    Joined: Jan 23, 2015
    Posts: 268

    WP38
    Member

    Great thanks. Being ignerant of transmissions this part would cause the transmission not to shift in any gear? thanks will get a new part.
     

    Attached Files:

    Last edited: Oct 8, 2017
  29. WP38
    Joined: Jan 23, 2015
    Posts: 268

    WP38
    Member

     
  30. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,950

    gimpyshotrods
    ALLIANCE MEMBER

    Not exactly. You should still be able to "find" a gear, but it won't stay in it.

    That spring and roller ride on a "rooster comb" which stops the shifter movement at each gear, PRND21.

    If you manually turned the shift shaft that sticks out the side of the transmission, it should go click-click-click, stopping at each gear.

    With a broken spring, it will turn free, stopping only when it can no longer turn due to physical interference.
     

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