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48 Chevy 2-dr Sedan going from 350 turbo to 200r4????

Discussion in 'The Hokey Ass Message Board' started by COS, Oct 26, 2010.

  1. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
    Member
    from KCMO

    OK here's the deal I have a 48 Chevy 2dr sedan with a 350 turbo that is getting weak.... I kept the factory steering colum and used the three speed shifter to shift the 350 turbo....

    I want to swap out the weak 350 turbo for a built 200r4 for the simple fact that I want an over drive. I was told that the over all length is the same as the 350 turbo so I will not have to change the drive shaft and that the mounts are only a 1/2" difference......

    The big question is... Will I be able to use the same shift linkage I.E. my factory colum with the three speed shifter??? Or will I have to change it all together?? Are there any other problems that I am over looking here???

    -COS
     
  2. drptop70ss
    Joined: May 31, 2010
    Posts: 1,152

    drptop70ss
    Member
    from NY

    Linkage will hook up the same way, you may not be able to manually put it into low gear (no big deal unless you are racing). You will also need to get the TV cable set up correctly, TV cable controls line pressure and shift points, get it wrong and you can burn up the trans. Also need to wire up the lockup for the converter. Th350 has a kickdown cable that isnt needed for the trans to work, the TV cable is not a kickdown cable.
     
  3. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
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    from KCMO



    Thanks for the info...
    What is the reason for it not going in to low manually?? Is it a different throw or in a different location?
     
  4. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
    Member

    I have never done the swap with a converted 3 speed manual collumn, but I suppose anything is possible. Of the 2 I have done with a TH2004R, one was in a '63 Impala (original 2 speed PG collumn, used Lokar rod type linkage), the other was an OT Corvette with a floor shift. If you're currently shifting a TH350 with it, I'm sure it could be made to work, but the linkage may need to be modified, or replaced with a Lokar universal style (or make your own). Your "built" TH2004R may have already deleted the lockup; I didn't use it in either car, and still got over 20mpg in both. Geometry needs to be correct for the TV cable (PM me with what you're running and I can probably help), but other than that its almost idiot proof.
     

  5. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
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    from KCMO

    How different is the location and shift linkage on a 200r4 to a 350 turbo....
     
  6. I swapped mine, and they are in the same place as far as I could tell.
     
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,678

    gimpyshotrods
    ALLIANCE MEMBER

    The shaft for the shift lever on the transmission is in the same position in space. The lever on that shaft is the same throw too. GM transmissions are designed to interchange in the same chassis.

    The TH350 has PRND21 in the same throw at the TH200R4's PRND321 (or PRN(OD)D21). If you can get it into first now, you will be able to get it into first with the 200R4.
     
  8. wingman9
    Joined: Dec 30, 2009
    Posts: 804

    wingman9
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    from left coast

    I hate to be the bearer of ill tidings but the trans mount on a 200 4R is the same as a 400, not a 350. Unless you have a removeable, and easily moved, trans crossmember you'd be a lot better off with a 700R4. The trans mount is in the same place as the 350 and getting a driveshaft cut is cheap and easy. Also there might be a difference in the trans input shaft between the 200 and the 350. I don't know for sure about that part. With the low first gear in the 700 it's also a lot easier to get the car rolling. Check this site for dimensions:
    http://www.tciauto.com/Products/TechInfo/trans_dims.asp
     
  9. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
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    from KCMO

    Man that is good news!!

    From what I have read it is only a half inch or so difference wich I can handle the fab on that for a lot cheaper and faster than having my driveshaft cut... I think?? I also have read that the 200r4 has a lower first gear than the 700 wich will get you out of the whole quicker.. Have I read some wrong info or am I not reading it right??? I am half polish....

    But you do bring up another good point about the input shaft... Anyone have an answer to that problem??? Does the 200r4 use the same input shaft as the 350 turbo???
     
  10. Moondog13
    Joined: Sep 7, 2006
    Posts: 738

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  11. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
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    The TH200R4 mount is further back, more like the TH400, but if you have the ability to cut and weld steel it isn't a big deal. An existing crossmember could be modified, or a new one built from scratch (or use a universal type from Speedway), for far less time/expense than would be involved in cutting down the driveshaft. The TH700R4 mount isn't in the same place as either TH350 or TH400, so you're going to have to move/mod the crossmember anyway, no matter which trans you have now.

    None of the mentioned transmissions use the same input shaft, so I'm not sure whats the point of that comment. The convertors don't interchange. Any flexplate that accepted a TH350 will accept a TH2004R.

    I like the TH700R4, and its later electronic versions, but in most cars I deal with the 200 is a better fit, and less hassle. I do prefer the TH2004R's gearing, though.
     
  12. wingman9
    Joined: Dec 30, 2009
    Posts: 804

    wingman9
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    from left coast

    Gear ratios for the 700R4: 1st - 3.06, 2nd -1.63, 3rd - 1.00, 4th - 0.7
    Gear ratios for the 200 4R: 1st - 2.74, 2nd - 1.57, 3rd - 1.00, 4th - 0.67
    Look at the site I attached for mount locations.
     
  13. wingman9
    Joined: Dec 30, 2009
    Posts: 804

    wingman9
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    from left coast

    I guess I mispoke. I meant the output, ie the yoke at the front of the drive shaft. I also prefer the 2004R gearing - in a light car. A '48 Chev isn't exactly a lightweight.
     
  14. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
    Member

    Output is the same, whether going from a Powerglide (not the original iron one, but a later style) or a TH350. To me that is the best feature of the whol swap...not having to cut and rebalance the driveshaft.
     
  15. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
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    from KCMO

    Ok so the mounting point is further back so I need to redo tranny cross member not sure how I got that crossed up... That shouldn't be that big of a deal other than my master cylinder is mounted to the one I have now...


    So can anyone confirm the out put shaft being the same on the 350 turbo and the 200r4??
     
  16. check with the guys over at www.chevytalk.com they could probably help. those transmissions were used behind turbo V6's in grand nationals doing 13's so your should be fine. post some pic's of your swap for the next guy.
     
  17. drptop70ss
    Joined: May 31, 2010
    Posts: 1,152

    drptop70ss
    Member
    from NY

    th350 and 200r4 use the same output yoke, also the same as the 700r4. I have 5 or 6 CZF 200r4s on the shelf, normally use them in place of TH350s but this time am putting a 700r4 in my 37 buick for the better first gear ratio and my 3:08s. 200r4 works great with 3:73 rear gears if you got em. Not all 200r4s are the same, GNs used the BRF valve body and a better governor, CZF is the other good VB used in 85-88 monte carlo super sports. Non HP 200r4s will have lower shift points, fine for regular driving, just not going to shift at 5500 stock.
     
    Last edited: Oct 27, 2010
  18. chevyfordman
    Joined: Oct 4, 2008
    Posts: 855

    chevyfordman
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    I run a 700R4 in my 48 so if you need any thing to look at come up and I'll show you, I have a lift and live a few miles north, I believe, I have the measurements.
     
  19. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,678

    gimpyshotrods
    ALLIANCE MEMBER

    Most drive shaft shops only charge a nominal fee to shorten a drive shaft.

    I have paid as little as $50, and the last one I got shortened for a 12-pack of Sierra Nevada Pale Ale.:D
     
  20. chubbie
    Joined: Jan 14, 2009
    Posts: 2,307

    chubbie
    Member

    if you are from KC, AAA transmissions in springfield is where i got my 200R4.. talk to Danny, best trans around for the money!!!

    trans mount is 6 5/8 back from the 350. drive shaft is the same. the trans shift linkage is different. can't remember but i think its back about an inch... redid the column shift linkage on my '41 chevy, and it works fine. i can't get low but works fine with out it. use a lock up converter, and use an adjustable switch to kick your converter in and out..if you cruise at "lock up" speed you will have a lot of over heating issues!! put in a trans. temp gauge! setting the TV cable is a bitch!! study , research the TV cable..don't go to a GM mechanic for help with the TV cable.... they only know one thing, carb wide open "click" the clicker and its set... bull shit!
    I know guys that ruined the trans because they listend to these guys!!
    your set up is not GM! and it needs to be set up to work on your car!!!
    good luck!
     
  21. COS
    Joined: Dec 14, 2006
    Posts: 729

    COS
    Member
    from KCMO

    Where do you have your master cylinder mounted at??

    What is the reason you can not get it in low??
     
  22. chubbie
    Joined: Jan 14, 2009
    Posts: 2,307

    chubbie
    Member

    Hi COS
    I can't get it in low because the detents in the steering column don't alow for another gear. I'm shure that more time spent, with some fab work it could happen. i tryed to adjust it out and found it would pop out of park!!!!! I need park more than low!
     

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