My Swap From a T18 To a 700R4

Discussion in 'General IH Tech' started by schrempp_b, Sep 3, 2020.


  1. schrempp_b

    schrempp_b Farmall Cub

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    So after some debate I’ve decided to swap the 4 speed in my 71 Scout II for a 700R4. To summarize the why, basically because I’ve got tired of driving a nice Scout with an old truck transmission, which needs work anyway. Her days of hard wheeling are over so I don’t find myself wanting a real low first gear. And driving it in town, while totally doable, isn’t that great. Would be nice to be able to pop out into traffic a little easier. Yes, I could swap in a 727 for less time and money, but if I’m doing all that work, OD would be nice.

    For a little reference, this is the build thread for this Scout up to this point. And this is another I started on the merits of doing this swap in the first place. I’ve got a good local trans guy who knows 700’s that’s doing most of the heavy lifting, basically building the trans and transfer case and getting it bolted up. Then I’ll be taking care of whatever is left. I’d like to do it all myself, but just don’t have the time.

    First off some parts planning:

    Shifter console – I want to keep the stock Scout II shifter console and have every gear (OD, 3, 2, 1) selectable. Mike Moore at ScoutCo has a kit for it. This is a bracket that goes on the trans, a modified shift gate, and an arm that goes on the transmission. All you need is the stock console, shifter cable, two cable clamps, and the small clevis fork at the transmission end of the cable.

    Transfer Case is going to get a similar setup in that I want it to look stock, so I’ll be fabbing up some linkage later on.

    Also needed a flexplate, hub and bolts. Got those from a guy locally. Going to need the pedal assembly for an automatic as well.

    Then the adapter kit that bolts the 80’s GM technology to the 60’s IH technology. (lol, why am I doing this again?) This comes from IH Parts America. Nothing too complicated there, just call them and order it.

    Then we need to deal with the TV Cable. If you don’t know about that, just know that it’s super critical to not destroying a 700. Plenty of info out there on it, but basically it moves a cable in response to the throttle position and has everything to do with the shifting in a 700r4. The carb I’ve got is the ‘new’ Holley 2300. They make an adapter that bolts onto the throttle bracket. The TV cable connects to that, much like the original GM setup.

    The transmission itself is a ‘K’ Case my trans guy found and rebuilt. This is a heavier case that GM used in the trucks, vs the case they used in cars. This also has what they call a 'structural' cover for the torque converter. I'll need to do some fabrication to make that work with the 304.

    Transfer case is an NP208. This has the rear slip yolk output, which adds some length to the setup. My trans guys is confident this won’t be too long for a Scout, but that seems to contradict a lot of anecdotes I’ve gathered from other folks. Fine with a stock set up, but with a lift it just depends. So we’ll see.
     
    Last edited: Sep 3, 2020
  2. schrempp_b

    schrempp_b Farmall Cub

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    The old stuff came out pretty easy, not much to that. For a trans shop anyway, lol. Then came the adapter. Right away they ran into a problem with not being able to line things up. Eventually discovered the nose of the starter was sticking out past the face of the adapter. After some head scratching and digging around on here, I learned about the mysterious shim that went between the starter and the block on auto equipped Scouts. Got a hold of one of those and then it all went together.
    He then worked out a crossmember that I think should work well. Also got the rear driveline shortened and bolted up. So at this point it’s my turn.
    IMG_20200715_162246.jpg
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  3. schrempp_b

    schrempp_b Farmall Cub

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    First thing I decided to tackle was the trans cooler lines. I decided to go with hard lines with a short rubber section to isolate the trans, which moves a bit in relation to the frame / radiator. I tried my hand at bending some tube but didn’t really like how it was coming out. Then I found out you can get proper pre-bent lines. Those of course are for the 727, but I figured that would at least get me from the radiator to the back of the trans, then I’ll use my short rubber pieces at that end. My trans guy put two short pieces of hard line coming off the trans for me to attach to, so pretty simple.
    IMG_20200903_122119.jpg

    It’s a little loose and sloppy right now, I’ll need to clean it up after I get a cover fabricated for the torque converter and flywheel.
    IMG_20200903_122210_1.jpg

    Before I hooked them up, I ran a can of aerosol cleaner through the oil cooler in the radiator to make sure I wasn't about to flush a bunch of crud into my new transmission. That's a process I only recently learned about, but it's easy to do and you can get the cleaner at any parts store.
     
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  4. Ron A

    Ron A High Wheeler

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    Have you figured out the dust cover situation yet?
     
  5. schrempp_b

    schrempp_b Farmall Cub

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  6. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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  7. schrempp_b

    schrempp_b Farmall Cub

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    Yeah, I'm just hoping it doesn't come down to that. The angles don't look too terrible at the moment, but needs a good road test to see if it's at least smooth when it's level.
     
  8. schrempp_b

    schrempp_b Farmall Cub

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    The shifter console went fairly easily. I took apart the old one and cleaned and lubed it before I did anything else. Cut off the old shift gate, the new one just bolts on using the same bolts that hold the shifter in the access panel on the trans tunnel. Hooked up the new cable, bolted the bracket to the pan on the trans, clamped the cable to the bracket. Then the small arm goes in place of the original one on the transmission and the clevis fork from the end of the cable attaches to that. That arm needed just a little grinding to get some more clearance in it so it would swing through the full range of motion. Took some fine tuning from each end of the cable to get it just right but I can select each gear and it all works pretty nice and smooth.
    IMG_20200822_151207_4.jpg IMG_20200901_192510.jpg IMG_20200904_141601_1.jpg
    Had to rig up a reverse light switch. Used this switch: VT16051C2. Annoyingly, this one doesn't have the lettering printed on it like the amazon picture so if it goes out I'll probably be doing some guessing.
    IMG_20200904_142053_1.jpg

    Even got a new indicator with OD:
    IMG_20200904_141908_2.jpg
     
  9. schrempp_b

    schrempp_b Farmall Cub

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    The linkage for the transfer case proved more difficult than I thought it would be. Just kind of tricky to figure out the geometry that gets the proper amount of ‘throw’ in the rod that moves to actually shift the transfer case through its range. Made this bracket that bolts to the bottom of the transfer case. This is what holds up the shift lever and gives it its pivot point.
    IMG_20200909_112259_1.jpg
    Welded a tab to the shift lever once I figured out just where it needed to be.
    IMG_20200909_112107_1.jpg
    For the rod that connects that to the transfer case, I used one end of the clutch rod and one end of the rod/arm that was already on the transfer case and welded them together.
    IMG_20200909_112127_2.jpg

    So here's the whole thing in its approximate configuration when it's all in. Deceptively simple looking for something with probably 8 hours of trial and error in it.
    IMG_20200909_111935.jpg
     
  10. schrempp_b

    schrempp_b Farmall Cub

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    At the moment, I've got no exhaust on the passenger side. That needs to be redone to work with the 208 and cross-member. Can't get that done for a couple weeks so I can't actually drive the thing yet. So I still don't know anything about how it will drive beyond just moving it around a little. I'm hoping to have all this miscellaneous stuff worked out by then so I can go right into some road testing.
     
  11. schrempp_b

    schrempp_b Farmall Cub

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    Got the torque converter cover worked out. Used the factory cover for the 700r4, the sheetmetal piece for the IH flywheel cover from the T18 and a piece for a 727.
    Here's the three. Had to cut the 700r4 cover like shown.
    IMG_20200914_150216_1.jpg
    Bolted together the IH pieces and welded a couple tabs onto them that match up with two threaded bosses on the 700 cover.
    IMG_20200914_150754.jpg
    Goes together like so. You can see there's a gap between the 727 sheetmetal piece and the aluminum 700 cover. I'm not too worried about it; I think it's pretty well covered up to keep the crud out.
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    Last edited: Sep 14, 2020
  12. schrempp_b

    schrempp_b Farmall Cub

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    Got the exhaust done. Went from duals back to a single for simplicity. Also think I’ll prefer it to the duals for the reduced exhaust drone inside. I left the guy to figure out how to do it. He ran it between the sumps on the oil pan. Looks like good work, but not sure how I feel about it. Looks like I can still get the oil pan off without too much difficulty. Think I’d just need to unbolt the pipes from the manifolds and let it hang down some. Just resealed it so I don’t plan to find out anytime soon. Not sure what a better way of doing it would be that didn’t interfere with something else or hang down lower than I like.
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    While he was at it I had him try to do something else with the flanges at the manifolds, which I have never been able to keep sealed for long. They have always loosened up and then blown out the gaskets. I’ve tried lock nuts, lock washers, double nuts, etc. When I would tighten them up, the flange would partially come into contact with the manifold, so I think that was part of the problem. Apparently that was because the pipe was a touch bigger than it should have been, so the donut was going further down than it should have. Also had him redo it without the exhaust flapper on the passenger side. And he added some springs to keep it under tension. No leaks and sounds good!
    IMG_20200919_183703_2.jpg

    So now back to the trans shop to get the TV cable dialed in and do some road tests. Getting closer...
     
  13. schrempp_b

    schrempp_b Farmall Cub

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    Ended up needing to do some modification to the TV cable bracket to make it work. The position of the bracket was too far forward / too close to the carb, which put too much slack in the cable. So I extended it back about an inch and a half. I think this is necessary mostly because the bracket is made for a four barrel holley. They don’t make one that’s spec’d for the 2bbl 2300. On a four barrel, that back ear that the bracket sits on would be about that much further back. So once it was sitting in about the right place, I followed the adjustment procedure. Basically push the button in and slide the cable housing all the way towards the firewall. Release the button, then move the throttle to wide open. That pulls the cable housing forward in the adjustment mechanism to what should be the perfect position and it should be dialed in.

    Here's the unmodified bracket. The circle on the right shows that the end of the cable housing is too close to the throttle linkage, and the circle on the left shows the crimped end of the cable being too far out, and thus has too much slack in it. You can sort of overcome this with a universal type of cable where you trim the cable to length and put a screw type throttle stop on it. The downside of those is that they can come loose. This type is a tad more permanent. You can also see in this picture the L shaped arm that goes on the throttle linkage, stamped with an H. This is the most critical piece of this setup as the point the TV cable attaches to needs to be a very specific distance and angle from the throttle shaft. Otherwise the travel in the TV cable as it relates to the throttle position is wrong.
    IMG_20200903_104551.jpg

    After modifying the bracket and adjusting it things are positioned much better. I also added a little brace that goes to that vacuum fitting to keep it from being able to pivot from side to side since it’s only mounted with that one bolt on the carb ear.
    IMG_20200929_183558_2.jpg
     
    Last edited: Sep 29, 2020
  14. schrempp_b

    schrempp_b Farmall Cub

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    After working out the TV cable I can finally take it on a good road test. And it’s AWESOME! The 304 and 3.73 gears feel like a good combo with this transmission. Hits OD at about 60 and cruises at 70 at 2200 RPM. Got a few more miscellaneous things to do like work out the front drive shaft. It's also got some vibration at certain speeds that I'm sure is coming from the rear drive shaft. Need to look at the angles real close and see if the pinion doesn't quite match the Tcase. But so far I’m pretty happy.
     

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