Automobile Transmission, why not?

Discussion in 'DIY Marinizing' started by Ken Gasch, Oct 5, 2004.

  1. Frosty

    Frosty Previous Member

    Did you notice that Celts kit included the line pressure increase to hold clutches and bands. I did say you would need to do this didnt I.

    What did you do with the Modulator Celt?
  2. whitepointer23

    whitepointer23 Previous Member

    all the boats i have been in with autos are as they came out of the car, convertor and all, work fine, but i am talking about medium speed launchs not 400 hp performance boats.
  3. Tiki 38 Zaphod
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    Tiki 38 Zaphod New Member

    Hi Tom.I am thinking about a Nissan SD 22 Diesel with either a manual or auto Transmission Thrust and marinizing are no problem. what do think about the transmissions.
  4. trini
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    trini New Member

    all you got to do is make a outboard foot with 2 rear wheel differential the two must be the same ration and weld off the planetary gears it will work
  5. bob21635
    Joined: Mar 2015
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    bob21635 New Member

    Cummins 5.9L Diesel Allison Transmission from Schoolbus

    SVSeeker from installed a non electronic Cummins 5.9L and Allison Automatic Transmission in his 73 ft DIY steel hull Motor Sailer. It also has a controllable pitch 3 blade propeller with thrust bearing. He will only use first, neutral, and reverse at a 3.45 reduction. Plans on sailing to Venezuela once a year to top off his 2,000 gallon fuel tanks at $.17 a gallon!

  6. black_sails
    Joined: May 2016
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    black_sails Junior Member

    Even though the original postings i'm responding to are almost 12 years old i'll comment hoping someone else has followed the thread and might know. :)

    I would like to see pictures or/and mechanical/CAD drawings of peoples fabbing up thrust bearings off the end of the transmission. Cyclops2 i'd love to see even a sketch of it. :) It should be pretty simple but since i'm not studied in mechanical engineering (yet) seeing helps me understand - I mean I don't feel ready to go design one myself. I'd ideally want it strong enough to withstand a 'catastrophic impact' - ie whatever forces caused by a collision just break the driveshaft or go into the thrust support - not further into the transmission. Think of it like a fuse blowing - fuses are designed to blow when loads are exceeded to protect more expensive stuff on either side.

    I guess i'm curious if the whole thing just adds a few inches on the end of the transmission or what. I would actually like to use this exact propulsion method in one or more future boats if I ever get to build them - it seems like a clever low cost way to solve a problem. If nothing else to solve it for awhile until you can upgrade. One some people for some reason were griping about but a Rolex tells time and so does a Casio - it just depends whether you need to do a job at the lowest cost possible or if you are trying to enter into an exclusive social club. Myself i'm a $9.99 casio man. :p

    I would think a ujoint has problems with propeller speed varying unless there is no angle in it normally. (I would have assumed a CV joint would be needed if there is any permanent angle change in the driveshaft) For that matter a ujoint or CV joint could provide that 'fuse' even though it would more break from rotational force instead of linear force, at least it's a breakpoint.

    For others following the thread I could not understand what EvilBoater was trying to contribute on some things, I can see no use for a high stall converter in a marine application. The purpose of a high stall in dragstrip racing is to let the engine get up into it's powerband before you even launch in first gear often to keep the drag slicks on the very limit of traction. It helps some in 2nd too. I don't see any prop being so oversized that 1st gear already isn't enough to turn it properly in the water and a high stall converter will heat up substantially under constant high torque output both wasting power and burning out the transmission without cooling. If anything you'd probably want a lockup converter for economical cruise which can often be rigged with a simple manual switch to engage them. A manual switch can also make it engage in 2nd which is not usually supported outside the newest transmissions. Manual valvebodies might make sense too - some of the GM turbohydramatics were supposedly very simple to convert to manual yourself.

    Curious what the people saying they arent running torque converters are doing, how you even shift R-N-D when I thought the converter prevented the slam into gear suddenly engaging from the bands/clutches - i'd think it would be hard on them?

    Every automatic uses some of the engine power - hot rodders often say a Powerglide will take 18hp, the 3 speeds all 40-65hp. (TH350, TH400, C4, C6, Torqueflite 727) This only becomes a negative in top gear and a lockup torque converter would eliminate that downside because it gives a 1:1 link.

    Crowsridge mentions an FWD transmission - i'd like to see how that works acutally. I'm not sure how you think you'll turn them different ways to get counterrotation. (not attacking just... how do you mean?) If you use the entire front axle and everything ie the shafts going to the tires that's after another 4:1 reduction which is probably too much... if just the transmission to use it's going to come back alongside the engine on normal transverse engines. Like to know if you ever moved ahead with that or if there would be a way to do that (get counterrotating props easily) or how important it even is to have them. FWD transmissions in general might provide a way to shorten the length of such an install - even for V8's if you use the late 70's/early 80's Buick/Olds/Pontiac/Cadillac type transmissions ie TH325/425/475 (the last for the GMC FWD Motorhome applications) which were longitudinal mounts (and would keep the same 'look' if you like it that way as a conventional pair of inboards going north-south, just reversed south-north).

    I wonder whether the side discussion about parking pawls and a spinning shaft in neutral needed expansion/would love to know in future (even 5 years in future from future posters! I wont be building my boat set up like this for at least 5 years yet anyway) if thats a problem and if there were some easily implemented solution, even if it involved welding on a brake drum on the shaft or something. However it's possible the transmission danger is not too bad because the amount of spinning momentum energy is not that much - it's not like shifting into park on a 4000lb car while still moving 8mph, you're only stopping the spinning weight of that shaft off the back and however many pounds it weighs and not instantly because the prop is softened by the water acting like it's own torque converter. Perhaps that's no big deal... i'd love someone who knows better to enlighten me.

    A final comment is that transmissions should actually live fairly well under high power in this use I would think with good line pressure and lockup converters. Part of what breaks transmissions are the shock loads caused like when drag slicks hook up, then spin, then hook up again - the weight of the driveshaft, LSD gearing, wheel and tire combo's is what, probably over 100lbs (and the wheel/tire with alot of leverage) spinning catching spinning, those jolts of torque and shock is what does it. Or like 4x4 off roaders sometimes break things with totally stock power 4cyls going over ground that's slippery then grabs then slippery again. (ie patches of gravel on the asphalt, or ice patches) The constant smooth holding of torque is likely to be far better tolerated on any decently stout transmission even if putting more than stock power through. The only shock loading source would be if your prop completely left the water as you jumped other peoples wakes i'd think...

    Hope I contributed something useful (along with the questions I hope others may be able to eventually answer)...
    DogCavalry likes this.
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