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Finally Started The Sm420 To Dana 18 Swap

Discussion in 'Builds and Fabricators Forum' started by 1969jeepercj5, Dec 9, 2019.

  1. Dec 9, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Well I finally got my parts in from Novak and had a little time this weekend to start on things. I had sold off the T14 in 2018 so this has been in the works for a few years now. Time and money are of course the two biggest issues, and being a wildland firefighter basically eats up my whole summer. I still need to find a good sm420, I got one for free but the teeth are too rotted for me want to run it. I also need to decide what I want to do as far as clutch linkage goes, I'm leaning towards the AA chain clutch set up.

    [​IMG]
    [​IMG]
    [​IMG]
    I was able to at least get everything mocked up. from a quick measurement it looks like my rear driveshaft will be about 16" long and the front will need to be extended about 4". I only have a 1 inch lift so the driveshaft angles actually look really good. I've also been tinkering around getting the transmission tunnel to fit, I'll try to get some more pictures up soon.
     
    CJeep5, sgogpn, 73 cj5 and 7 others like this.
  2. Dec 9, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Did a little more work today. I was able to finish welding up my new trans tunnel, I was going for a fairly stock look and I think it came out pretty clean.
    [​IMG]
    Dont mind all the booger welds, and the mess inside the cab. I've since ground down most of the welds, but still haven't cleaned out the cab :bananatool: .Ill eventually smooth out transmission cover and probably put a little bit of bondo on before I paint it. Any way Im probably going about this all out of order but it all has to get done eventually :D. Anyway here are a few more pics.
    [​IMG]
    [​IMG]
    [​IMG]
    Ironically I put some BBQ paint on it then set it on the smoker... Just wanted to get a little paint on it to try and help it from rusting while I slowly get the jeep back together.
     
    fhoehle and Twin2 like this.
  3. Dec 9, 2019
    timsresort

    timsresort New Member

    South Lake Tahoe CA
    Joined:
    Jan 22, 2014
    Messages:
    15
    Looks good. I have done this swap on a few Jeeps. If I were you, I'd consider a hydraulic clutch setup while you have it apart, especially if you see disc brakes in your future, or you still have the single MC. The chain linkage works fine, but the real reason to go hydro is getting the brake master cylinder up off the frame. Yes, it requires swing pedals, and that is some work, but the payoff is worth it.
     
  4. Dec 10, 2019
    Jeepenstein

    Jeepenstein Me like Jeep..

    Middle TN
    Joined:
    Jun 15, 2003
    Messages:
    1,679
    Nice man, did mine years ago.. Loved it while the jeep was still moving..
     
  5. Dec 11, 2019
    CJeep5

    CJeep5 New Member

    California
    Joined:
    Mar 23, 2018
    Messages:
    19
    What bellhousing are you using? Did you have to do any cutting or drilling to mate it to the sm420?
     
  6. Dec 11, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    I'm using the original Dauntless BOP bellhousing. I did have to drill out the two bottom holes on the bell housing since the sm420 bottom bolt holes are threaded. So you run the bolts from the inside of the bell into the transmission on those lower bolts, the tops go in from the transmission side into the bell like usual.
     
    CJeep5 likes this.
  7. Dec 11, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    definitely an idea, I do have a cj7 clutch master cylinder that I could theoretically use. I have also heard of people using a Toyota land cruiser set up.
     
  8. Dec 11, 2019
    durk

    durk Member

    Ontario/Canada
    Joined:
    Jan 6, 2005
    Messages:
    197
    590B7943-97AC-46B1-99DC-0F081E052A30.jpeg You’ll love the swap. Upside down Cake pan also works good... with all the fab work 590B7943-97AC-46B1-99DC-0F081E052A30.jpeg
     
    fhoehle and Cowboyjeeper like this.
  9. Dec 11, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    haha never would have thought to use that, but yours turned out really nice.
     
  10. Dec 12, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Anyone have pictures of an sm420 with a single stick set up? with the stock setup I couldn't get any movement out of the lever due to the linkage getting bound up on the transmission hump. I thought if I reworked the S shaped plates that go across the two rods going into the transmission I would get more pull, but that hasn't seemed to work so far.
    [​IMG]
    Here are the S shaped plates I was referring to. I cut and welded them in more of a U shape, allowing them to clear the reverse bulge on the trans. This didnt work but this is where I'm at currently.
    [​IMG]
    This was a sloppy mock up just to see if i could get any movement out of the transfercase. No luck so far
     
  11. Dec 12, 2019
    Lilbuff63

    Lilbuff63 Member 2019 Sponsor

    Sonoma County Ca
    Joined:
    Jan 12, 2014
    Messages:
    107
    Here’s a couple pics before I installed mine. The guy I bought it from had already rebuilt and adapted the sm420 to the Dana 18 before he decided not to finish his project. It works pretty good, just as clunky as any Dana 18. BECBA53B-8C9A-4B9E-ABEA-BB775D5D2585.jpeg 68AF5BBE-017D-456B-ACA0-080B0077DBDA.jpeg
    Maybe swap your linkage to the other side of your shifter?
     
  12. Dec 12, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Haha that just might work. Why didn't I think of that. Ill have to test that out next day I have some time. Thanks for the pictures
     
  13. Dec 13, 2019
    desertsled

    desertsled New Member

    Phoenix, AZ
    Joined:
    Aug 22, 2019
    Messages:
    3
    I'm just in the beginning stages of this swap while the jeep is down to the frame. Can't wait to see how it comes out,
     
    1969jeepercj5 likes this.
  14. Dec 13, 2019
    Norcal69

    Norcal69 Out of the box thinker 2020 Sponsor 2019 Sponsor

    Northern California
    Joined:
    Sep 6, 2014
    Messages:
    1,371
    Have you considered twin sticking it?
    This is what we did with Steve's 71. His is a 420 just like yours.... just late model reverse light top cover. Shift levers could be fabbed up pretty easy.

    [​IMG]
     
    1969jeepercj5 likes this.
  15. Dec 13, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    I have thought about the twin stick setup and that seems to be the most common route. I'm definitely in the minority, but I actually enjoy the single stick setup. If i'm unable to get the shifter to work with a little more tweaking I probably will end up going to twin stick route.
     
  16. Dec 14, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Well I was able to make enough adjustments to the transfer case linkage to get it to move through all the gears. I just need to adapt a more permanent plate that mounts to the transmission now. Unfortunately I didn't get any pictures today, should have more when I finalize my shift linkage.
     
  17. Dec 16, 2019
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    OK I was able to make some progress yesterday, I was finally able to make the tcase linkage work. I had complicated it from the start, by trying to change the angle of the shift plates. I ended up cutting and welding them back into their original configuration. I also adjusted the linkage at the base of the transfer case lever shortening it all the way. This allows for the full range of motion and it doesn't bind on the reverse bulge of the transmission.
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    [​IMG]

    I was also able to rework and fit the transmission tunnel, I put the Tcase lever in 2H and layed the plate down as aligned with the mounting holes as possible. Then I crawled under the jeep and traced out a rough circle that would allow for the full range of motion of the shift cane. Here's what I ended up with.

    [​IMG]

    I then decided to close the original Tcase hole, so I traced and cut some scrap metal and welded it in place.

    [​IMG]

    Then test fit both trans tunnel pieces to make sure everything would still work and had enough clearance.

    [​IMG]

    It was then time for a little bondo and primer. My goal has been to make it look at least as good as it would have come from the factory, if this setup was an original option. So as we know this isn't saying a whole lot as far as perfect body panels go :whistle:

    [​IMG]

    Here it is with a little bondo and primer. Sorry for the bad lighting, these short winter days make it hard to get too much done.

    Ive been doing this swap a little out of order as I don't have all the pieces quite yet. Im still leaning towards the chain clutch setup form Advance Adapters, even with some of its drawbacks, such as binding with articulation etc. I just feel more comfortable mocking that up then I do installing a hydraulic system. I originally had thought about doing power steering as well since I will have to modify my exhaust system anyway. But that opens up too many worm holes and turns this into more of a project than I want at the moment. When I go to power steering it makes the most sense to swap in a dana 30 NT since this is the end goal anyway and I should be able to get everything included with the axle such as the tie rod and maybe even pitman arm. I also have a line on an early postal steering column which only pushes me deeper into this never ending project, since I would grab the rear gas tank, possibly the 11" drums for the rear since I'm already running discs up front and probably some switches and things off the dash. So for now Im just going to focus on getting the transmission to work, getting my drivelines adjusted and getting a clutch setup that I like.
     
    fhoehle and ITLKSEZ like this.
  18. Feb 28, 2020
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    Project update.
    So I found what looks to be a late 60's sm420 at the local junk yard. The gears actually look to be in really good shape and there appears to be very little wear on the syncros. The bearings are even still good. I had planned to rebuild whatever transmission I ended up with, so I had purchased a rebuild kit off ebay several months back. I was waiting to tear into the kit until I had a good transmission, and I found the kit to be missing all seals, and one of the bearings wasn't correct :steamed:. Luckily I found this out before I completely disassembled the trans. Also ordered an AA chain clutch setup so that should be here shortly.
    [​IMG] Heres the trans.
    I brought the driveshafts to the local shop here in Chico. The shop was a little hesitant about being able to lengthen the front driveshaft since the tubing thickness and u-joints aren't very common?...
    Also my measurements for the front was 26-3/4" and 16-1/8 for the rear from center of U-joint to center of U-joint. Does this sound similar to what others have come up with?
     
  19. Feb 28, 2020
    Norcal69

    Norcal69 Out of the box thinker 2020 Sponsor 2019 Sponsor

    Northern California
    Joined:
    Sep 6, 2014
    Messages:
    1,371
    You should upgrade your u joints to the larger 1310 size. The v6 equipped Jeeps came factory with smaller u joints.
     
  20. Feb 28, 2020
    1969jeepercj5

    1969jeepercj5 Member

    Los Molinos...
    Joined:
    Apr 22, 2016
    Messages:
    60
    You're right the shop did say the front was a 1210 and the rear was a 1310? Would the 1310 work with the dana 27?
     

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