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sm420 fluid

Discussion in '40- & 55-Series Tech' started by jjhancock, Jul 25, 2005.

  1. jjhancock

    jjhancock

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    I'm getting ready to change out the fluid in my tranny, t-case and diffs. I know how much fluid I'm to add back into the t-case and diffs, but the sm420 I have not a clue. This post: https://forum.ih8mud.com/showthread.php?t=50284&highlight=transfer+case+maintenance

    shows all the fluids and the amounts for an fj40, but sm420 was not stock in an fj40. I asked the guy at napa and he couldn't even find the sm420 on his 'puter. I've read that you can just fill 'er up until it's full, and I know I could in theory measure how much came out of it and add that same amount back in, but I'd like to know how much is *actually* supposed to go in there.

    I'm expecting to pick up some redline MT90 today or tomorrow to complete the job. Thanks.
     
  2. Desertdave

    Desertdave

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    I have done it

    a couple of different ways. First few changes, I used the fill plug on the side and pumped it in. Hard to tell how much it held because the awkward access caused me to have much spillage.

    Last time I followed somebody's advice, pulled the shifter, and dumped in a whole gallon via the shift tower. A lot easier, cleaner, etc. I was loving' life, compared to the time and mess of an under-the-rig refill.

    HTH
     
  3. jjhancock

    jjhancock

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    Thanks for the reply Desertdave. I am thinking that I should go ahead and pull the shifter and dump the fluid in via the shift tower like you suggest. Since I still don't know the exact amount that I should be adding here, tell me how well your sm420 performed as a result of you just dumping a gallon in and being done with it? Seem like it was enough or just about right for good performance from your tranny?
     
  4. woody

    woody unhelpful spotter Staff Member Admin

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    pull the side fill plug, start dumping fluid in from the shift tower...don't be in a hurry, and when it starts to drool out the side, put the plug in quickly. A little overfull won't hurt a thing.

    Probably a two person operation, the bottom person may get lubed :D

    SM420 is a manual tranny from 1967-older on a chev truck...so your NAPA guy can find it later.

    I don't know actual quantities, rely instead on a 5-gallon drum and a pump (much cheaper long term, and much easier to fill with a pump)
     
  5. JasonH

    JasonH

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    Pull off the PTO cover and drill and tap a hole in it. I want to say that about 2/3 of the way up is the same level as the original fill plug.
    There's your new easy-to-access fill hole.
     
  6. dustin

    dustin

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    I also did this. I welded a bolt to the back of the plate though so I would have more thread, but I dont think you have to do that. I am running a rubber washer on the bolt. Works great!

    -Dustin
     
  7. CruisinGA

    CruisinGA

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    What about those of use that do not have a PTO cover? ;)

    Shifter method works for me... especially easy when your tranny tunnel is off too.
     
  8. Hossdog

    Hossdog

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    my personal fav for fluid is RedLine's MTL (Manual Transmission Lubricant) cuz its got some fancy stuff for the syncros.......and if you have a manual tranny that doesnt shift smooth as a babys ass put some of it in and you'll be amazed. Pretty pricey at about $10 a quart but I think its money WELL spent in the whole cruiser cost ratio.
     
  9. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    There was a post a while back about some gear lube additive or something to use in a 420 tranny, something about the GL-5 does not have the same additives that older GL had...


    For the life of me, I cannot find it.



    Redline MTL eh? Might have to give that a try....2nd gear is being a trud...



    :beer:
     
  10. jjhancock

    jjhancock

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    Power, I'd be interested in that post if you find it. The only thing I know about the tranny fluid is that I'm supposed to use GL-4 in it and the transfer case because of synchros. IIRC, GL-5 is supposed to be superior, but has sulfate or something or other in it, and that's supposed to be bad for syncros I'm told. I'm planning on trying the MTL as others have said great things about it as well.

    I'm hoping to get this job done this weekend as well get my carb back from Jim C. If all that happens and I don't break anything in the meantime, I'm goin' wheelin' this weekend!!
     
  11. CruisinGA

    CruisinGA

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    I am too, I was suprised to find that 2nd gear is being a bitch on a new tranny.. ???
     
  12. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    That may have more to do with the whole Gama-goat tranny using a truck top cover, as I sold one of the two new 420 gama-goat trannies that I had to Jim VanDeVen a few years back for his noc-noc truck, and he occasionally had shifting issues with his too...


    -Steve
     
  13. CruisinGA

    CruisinGA

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    Thats interesting. Oh well. :rolleyes:
     
  14. jjhancock

    jjhancock

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    Considering my sm420 came from a 1949 truck, the design can't probably be state of the art. Even though it's been rebuilt (and I have no idea how many miles are on that rebuild), I'm not surprised at all that I grind going into 3rd. Thankfully it's really only 3rd that gives me so much grief. I'm anxious to try the MTL. If it makes any improvement, it'll be worth the extra coin to get the good stuff.
     
  15. Hossdog

    Hossdog

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    Mine was tuff to get into all gears, had to give some extra push to get it in. Nothing crazy or anything, just annoying little extra muscle. Added MTL and it was slidin in and out like.....errr.....well lets just say it was feelin' good!
     
  16. Desertdave

    Desertdave

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    Sorry for late reply


    I noticed no difference in the performance of the transmission between the two methods/amounts of gear lube. Which was what I was hoping for. How often does the easy way out really work as well as the 'proper' way?
     
  17. jjhancock

    jjhancock

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    Things do not usually workout the easy way as you put it. My hesitation issues certainly didn't work out the easy way like I was hoping. It is good, however that I'm getting to know my rig pretty well and can work on it myself for the most part, so far anyway...
     
  18. greencruiser

    greencruiser

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    lucas oil additive can be used straight in gear boxes and stuff really helps those leaky seals

    i am running it straight in my tcase that was leaking pretty bad out of the front and rear outputs and it really slowed the leak down. also helps that cruiser gear whine a little

    should also help stiff shifting
     
  19. dgangle

    dgangle total rice SILVER Star

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    I have no first-hand expereince with the SM420. Educate me here. Does it not have a drain and side filler plug like the H42?

    If it doesn't have a side filler/oil height check plug how are you supposed check the level?
     
  20. CruisinGA

    CruisinGA

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    It does have one, but the cruiser tcase front output obscures it.

    I still have my tranny tunnel out so it hasn't been a problem yet.

    This is why some install a fill plug in the PTO cover, which is completely unobstructed.