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Technical Swapping out th350 for a 700r4 in a 1951 chevy

Discussion in 'The Hokey Ass Message Board' started by Ratrod.piper, Apr 10, 2014.

  1. Ratrod.piper
    Joined: Dec 30, 2013
    Posts: 38

    Ratrod.piper
    Member
    from canada

    Hello all,
    my 51 chevy coupe currently has a 327 pushing a TH 350 transmission.. I haven't gotten very far my project so far since I got it, hoping to put in some hours soon... One of the things on my mind is swapping out the old th 350 transmission and putting in a 700r4 mainly due to the cost of gas these days, I want to build a cruiser more than I want to build fast car.. I seem to have no problems locating a 700r4 in my area. However I'm wondering just what's involved.. Has anyone done this specific swap? Wondering specifically about cross member for the transmission, drive shaft.. And pretty much everything in between...
    Any Comments of advice would be appreciated
     
  2. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,371

    49ratfink
    Member
    from California

    the transmission mount for a 700R4 is about 10 inches further back than the turbo 350. I had a turbo 350 in my 49, and had to add another cross member behind the original to mount the 700R4. they are also bigger around so depending on how high up in the frame your motor is mounted there may be floor clearance issues. I didn't have any floor issues, just the cross member.

    pretty sure your current drive shaft will have to be shortened, I don't remember if I ever had a driveshaft in my car before I went with the 700 so that may be incorrect
     
  3. never done it in a `51 chevy , but i wouldn't think it would be too hard. i've messed with a few 700R4s and they are basically like th350, just a bit longer. i would guess the current transmission mount could be modified. the driveshaft will need to be shortened , the slip yoke for the two transmissions are the same

    then you have shift linkage and the TV cable to mess with
     
  4. scrappybunch
    Joined: Nov 16, 2011
    Posts: 281

    scrappybunch
    Member
    from nj

    Drive shaft will have to be shortened. The most important thing is the TV cable and how it interfaces with the carb and geometry of the 'pull'. If not correct it will burn up the trans. A better option is using a 4l60E with a separate controller to set shift points and firmness and TCC lock up, espec in a non stock vehicle. Price is worth the less hassle.

    Those 700 shift points are wacked, they would shift into 3rd way early, playing with valve body and governor springs is pita.
     
    Last edited: Apr 10, 2014
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  5. Scrappybunch beat me to it about the TV cable adjustment. VERY critical!
     
  6. I have a built 700r4 in an o/t truck and its great.
     
  7. TCI makes a bolt in cross member that is made for either TH350,TH400, or 700R4 and it's not that expensive. I put one on my 54 Chevy along with their power brake booster and it was a breeze. You will have to shorten your drive shaft though.
     
  8. gdub
    Joined: Sep 16, 2004
    Posts: 202

    gdub
    Member

    I swapped a 700r4 for the th350 in my F-1. My 350 had the same length tail-shaft as the 700r4 so the mount and drive-shaft did not have to be changed. The TV cable setup was not a big deal at all. I got a mount from the junkyard and adapted it for my engine, Mainly just made sure the cable lined-up straight with the throttle arm. Set it by adjusting the cable all the way in then taking the throttle to wide open. There are plenty of you-tube videos that show how to do it. For my truck it was all very easy to do, my son and I changed it out in one day in the driveway.
     
  9. elba
    Joined: Feb 9, 2013
    Posts: 606

    elba
    Member

    It is probably going to cost around a thousand bucks. Sit down and figure the payback time. I would leave the 350 in it. It is a good tranny. Take the thousand and spend it elsewhere. Just my opinion.
     
  10. Or stuff a 200r4 in it and no drive shaft cut and just add a 3" tab off mount, drill 2 holes, bolt it in and go.
     
  11. ebfabman
    Joined: Mar 10, 2009
    Posts: 601

    ebfabman

    A 200-4r is a better choice.
     
  12. Ratrod.piper
    Joined: Dec 30, 2013
    Posts: 38

    Ratrod.piper
    Member
    from canada

    200r4you say...hummm... did not consider that.. What kind of car would I pull that from? ... Seems like all I find are 700r4 listed on Kijiji in my area... Are there rare or something?
     
  13. Ratrod.piper
    Joined: Dec 30, 2013
    Posts: 38

    Ratrod.piper
    Member
    from canada

    by the way thank you to all who have chimed in...
     
  14. praisethelowered
    Joined: Aug 14, 2003
    Posts: 1,103

    praisethelowered
    Member

    I have a 700r4 for the first time in a old car- I have had 350's, C-4, powerglide and manuals . . .and got used to having the motor wound up on high speed freeway drives. But overdrive is really great. Even if it doesn't pay back quickly on gas prices you should also consider that the engine engine will be really happy on the freeway when you are driving fast and the rpm's stay low . . . totally worth it.
     
  15. JeffB2
    Joined: Dec 18, 2006
    Posts: 7,676

    JeffB2
    Member
    from Phoenix,AZ

    You will want a 1988-1992 donor for a 2004R common in Chevy Monte Carlo's these are non-computer and have the later lubrication upgrades,good article here:http://www.hemmings.com/hmn/stories/2011/01/01/hmn_feature26.html
     
  16. 48FordFanatic
    Joined: Feb 26, 2011
    Posts: 1,336

    48FordFanatic
    Member
    from Maine

    If you are lucky and have a TH350 with the long tail shaft ( 9 inch vs 6 inch ) then the transmissions are the same length within about 1/8 inch. The TV cable geometry and set up is extremely important , not complicated, just important that it be correctly. For whatever carb you are using there will be brackets available to provide the correct TV cable attachment and throttle position geometry. In my 48 Ford I run a TH 700R4 behind a 350SBC with an Edlebrock 1405 carb. I bought a kit from Bowtie Overdrives that provides the correct attachment and position of the TV cable . Bowtie Overdrives has a ton of good information on line. I set up my transmission one time and have never had an issue in the 20,000 miles I have driven the car.
     
  17. Hnstray
    Joined: Aug 23, 2009
    Posts: 10,759

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    When you say "cruiser", what does that mean? Mostly in town with occasional highway use or mostly highway driving at or above 50 mph?

    Consider that the OD transmissions DO NOT engage overdrive until about 45 mph. So anything under that is exactly the same as driving with your TH350.

    What rear axle ratio is currently in your car and what is the size and diameter of the rear tires? It may very well be that a rear axle ratio change would be of more benefit and less money than changing the trans.

    I know 700R4 trans are popular...and they deserve to be....but the 2004R has a lot to offer in a bit lighter weight, a bit smaller case size, less internal friction so use less horsepower to operate it and many people think it's ratio spread is better suited for some circumstances.

    In my opinion, you have a lot of questions to ask yourself, and answer, before jumping on the OD trans "bandwagon". Your car, your money, your decision......
     
  18. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    You will love the 700r4 or 2004r. The latter may be a little harder to find. They aren't a hard swap and the cable isn't hard to set up. People have been doing this swap for awhile now and it's pretty common. And yes..... If you don't adjust the cable correctly it will shift to early and it will also burn up clutches. That's an easy fix if you just order an adapter for the carb you are using. The shift points are adjusted with the cable.... No need to change springs etc. Inside the transmission like was posted earlier.
    When adjusting the cable just remember, the shorter you make the cable the later and firmer the shift. It also effects the kick down. I have mine adjusted perfectly where you don't need much pressure on the pedal for it to kick down a gear for passing. It drops out of lockup and downshifts like a dream.
     
  19. indyjps
    Joined: Feb 21, 2007
    Posts: 3,576

    indyjps
    Member

    Don't forget to wire in the brake switch to turn off the lockup converter when you hit the brakes. I've always just bought the kit to do it, but there plenty on the web to do it thru the brake switch. Read up on it, its been too long ago for me to give good detailed advice
     
  20. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    I don't even have the brake cutout on mine. Hardly even notice it. It drops out of 4th pretty quick after touching the brake anyway....as soon as it drops out of 4th the converter unlocks automatically.
     
  21. Ratrod.piper
    Joined: Dec 30, 2013
    Posts: 38

    Ratrod.piper
    Member
    from canada

    @ hnstray when I say cruiser, I mean something that I'm going to drive around.. And not just sitting around at car shows, and burger shop.. I don't want to build a trailer queen.. I want to be able to drive up to the cottage three and a half hours away, I want to be able to drive her to work I just wanna cruise in general make my everyday car.. Lord knows how long I have to walk on this earth and if I'm going to put time and effort and money into a car I'm going to make darn sure I'm going to use it... I got a long way to go on my car and I pretty much don't know what I'm doing but if I can scavenge of a nice 4 speed automatic.. And put it in a rack at my garage till I need it. or shall I say till I'm brave enough to try to install it.. But from what I read in that article Jeff reference I'm leaning towards the 2004r
    @jeffb2 thanks for that link very informative
    @48fordfanatic short-tailed, part is I got one of them big tall low Lokar taill mount shifters that was installed when I got it.. Little too big for me, not quite my style. But still a shame that I won't be able to use it on a 700 or the 200
     
  22. Ratrod.piper
    Joined: Dec 30, 2013
    Posts: 38

    Ratrod.piper
    Member
    from canada

    @txturbo. Thanks for the advice, worst comes to worst I literally live half a mile from the transmission shop up the street from me... But that's my fallback if I can't fumble my way through it lol..
    This is going to sound bad... But I still have not heard this car run since I got it... That 327 is looking awfully pretty in there... I need to get off my ass and install that wiring harness, and put in the distributor to fire her up..

    Somebody had asked about my desk... I know its a GM 10 bolt.. I have no idea what the gear ratio is, or if its a POSi .. Soon as the wife gets me a little garage time I'm going out to try to figure that one out too..
     
  23. sdluck
    Joined: Sep 19, 2006
    Posts: 2,206

    sdluck
    Member

    Do a search 2004r have a better gear split and were used in come olds cads and other gm,most have a multi bolt pattern bellhousing
     
  24. Custompainter99
    Joined: Jan 7, 2012
    Posts: 98

    Custompainter99
    Member
    from San Jose

    I have on in my 50 shoebox...the previous owner put it in. 1st your speedo wont work unless you convert it to mechanical drive vs electronic. 2nd you will need some type of 4th gear lock up because now the transmission is no longer computer controlled... I learned this all the hard way...

    Posted using the Full Custom H.A.M.B. App!
     
  25. damagedduck
    Joined: Jun 16, 2011
    Posts: 2,341

    damagedduck
    Member
    from Greeley Co


    Not always true, mines has a regular speed port.
    Here's a thread I started a while back. Do a search for 700R and you'll get plenty of ideas- maybe this will help?

    http://www.jalopyjournal.com/forum/showthread.php?t=791462
     
  26. I have a 200-4R in my Firebird and love it. I wouldn't think of running #.70 gears and 26" tires without it. I have a TH-350 in my Willys with 3.42 gears and 27" tires. I'm switching the Willys to a 3.08 or 2.73 rear gear. Why? Cost of the swap, simplicity of the swap and the use of the car.

    Overdrive will cost around $1000, and can go WAY higher than that. I would guess I have $1500 in mine. That's a rebuild with high perf parts, hardened input shaft, hardened sun gear shell, bigger bands, bigger servo, re-calibrated governor. Then there's brackets, cables, and that vacuum-electronic lock-up converter gizmo. If you need a stall converter, those can run as much as you checkbook can allow, but I've got $250 in mine. You'll have to check the yoke on the front of your shaft, as some 700-R4s had a different yoke, or so I've heard.

    A rear gear swap can run as low as $200, with used gears and an install kit. I do all my own wrenching, So you have to figure out what you can do and what you can't, and reconcile those costs. Swapping to a different rear gear can be easy, with some luck you can leave the housing in the car. If I went with the 2.73, I might need a different carrier, so that's why the 3.08 makes sense in my case.

    Because the Willys won't be doing any racing, there's no need for it to go fast. It's just for cruising and going to shows or the drive-in. If I want fast, I drive the Pontiac. I'm OK with that. For the money I would need to do an overdrive swap, I would have to drive for almost a decade to make up the estimated difference in cost.

    200-4R transmissions can be found in full-size Buick, Olds and Pontiacs, some G-bodies (Regal, Cutlass, Grand Prix, Monte Carlo) but the g-bodies didn't always get them. Look for the ones with 8 bolt holes, not just 6. 6 holers will only fit the BOP bolt pattern blocks, 8 holers will fit small block chevys and BOP blocks.

    One other thing, maybe I did something wrong, but I have to shift mine out of overdrive when I'm driving in town. the lock-up converter will lock and unlock due to low RPM and high vacuum. The car bucks and chugs...it doesn't like it. It won't drive like a modern OD auto. The guy at the transmission shop told me about this before I did the swap.( My brother in law had a S10 pic up that did that from the factory, so it's not unusual). So OD is for the highway, I just keep the shifter in "D" in town. Problem solved. I don't mind it, but it makes the car quirky, trying to explain that to another driver is a bitch. Trying to get them to understanding how to drive it is damn near impossible. So if the little lady is driving (or if you sell the car), that will become an issue. I was warned, I feel passing this on is important.

    That's all I know about it, I rambled on and repeated some stuff others said. Having done it, I can tell you my story and I hope you can take away something from it.
     
  27. 68vette
    Joined: Jul 28, 2009
    Posts: 306

    68vette

    My newly built 49 chevy fleetline has a 700R without lockup in it with a 3.42 rear end. At 40mph I am doing about 1000 rpm, at 60, I am doing 2000 rpm. Most of my running is around 1000 rpm...this is hard on plugs. I think I will pull it out of overdrive in the city just to save the plugs...gas mileage is terrible right now...about 10 mpg with a built 283...but I do play with it on take off.

    If I had it to do all over again...I would do what I had in my old 51 ford sedan. It had a built 305, turbo 350, and 2.79 gear, custom built quadrajet by me and my mechanic. Around town, it got 18mpg...out on the interstate, it got 24.4 and 24.6 running about 70 mph....no cable worries, etc.
     

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  28. Grumbler
    Joined: Mar 2, 2009
    Posts: 358

    Grumbler
    Member

    IIRC the 700R has a 3.00 to 1 first gear ratio and the 200R is 2.75 to 1. Just something else to consider, but if performance is not your prime factor then no big difference. Theres an urban myth that usually appears on threads comparing the two trannys that some will claim the 200R is "weaker" compared to the 700R - this normally from the chevy crowd lol - absolutely untrue, I have a 200R behind a 550 ft lb plus Olds 455 that sees regular play time at test and tunes and amateur bracket racing, the biggest problem I've had in seven years is replacing the O ring on the electrical connector for a leak. Get either one and you WILL like it....a lot
     
  29. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,371

    49ratfink
    Member
    from California

    here's what I did. the turbo 350 I had installed at first placed the mount right were the original trans cross member was, the photo shows the 700R4 and the new removable trans cross member a few inches behind the original
     

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  30. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,250

    gimpyshotrods
    Member

    I am not going to get into the which transmission is better argument.

    A 700R4 WILL fit under the stock floor in a '51, and those that share that floor pan. I have done several. There are numerous cross members on the marked, but I just cut the center out of the stock one, and make a new center, to accommodate the new mount location.
     

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