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Converting Dauntless 225 to Automatic

Discussion in 'Early CJ5 and CJ6 Tech' started by B_hester, Dec 30, 2015.

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  1. Dec 30, 2015
    B_hester

    B_hester Member

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    I Have the stock tuxedo park 4.88 locked axles, the dauntless 225 engine, and a failing t86aa tranny. With this set up I'm able to go about 55 mph. I absolutely love this engine in jeeps so I truly want to keep it and I'd also like to keep those hard to come by axle gear and locker in the rig, not just because its hard to come by but I love the feeling they give while driving it,but I want it to go freeway speeds because I'd like to make it my daily. Since Its needing a new tranny I've been looking into putting an automatic with an overdrive in there. I've really been looking into the th200r4 because it's got a pretty good OD in it, it doesn't require a computer, and it will fit the engine with out an adapter. My question is will I need to get a different flywheel or anything to switch the dauntlessvery less to an automatic? Because I love the low end power the dauntless' heavy flywheel gives so I really don't want to change it. Any help/guidance/knowledge is greatly appreciated!
     
  2. Dec 30, 2015
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    You will have to find a flex plate for the odd-fire. I'm not sure how long the 200R4 is, but I have a 67 Tuxedo with 4.88's, Dauntless, and a TH350, and the rear drive shaft is *short.
     
  3. Dec 30, 2015
    B_hester

    B_hester Member

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    So installing that flex plate should be the only thing really needed to use an automatic?
     
  4. Dec 30, 2015
    B_hester

    B_hester Member

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    The 200r4 and the TH350 are the same length with the same crossmember location
     
  5. Dec 30, 2015
    tarry99

    tarry99 Member

    Northern California
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    You could fix your current transmission and put a Warn 25% OD in there behind your Dana 18...........No change in drive shaft length , no new cross member, no need for a new flywheel .............and you get a 3.66 final drive ratio that will easily get you to 70 mph if you like.............really the perfect fix for a Jeep with a D-18 and manual gear box............PM if your interested in a Warn OD......I know where one is.
     
  6. Dec 30, 2015
    Daryl

    Daryl Sponsor

    Bonney Lake, WA
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    Much easier to put in an automatic if you get a later V8 grill which mounts the radiator farther forward then move your engine as far forward as you can. Every inch makes a difference when putting an auto in a short wheel base Jeep. If done this way, you can run a t350 and still have a rear driveline about 15" quite easily.
     
  7. Dec 30, 2015
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    Hi - where to start?

    Easiest one first - an automatic does not have a flywheel. Instead it has a flexplate. The flexplate has the starter teeth and connects the crankshaft to the torque convertor. The flexplate is very light compared to the flywheel, but you have no choice about this. Have you ever driven a 4WD with an automatic over rough terrain? It's a different style of driving, using both feet. Apply brake and throttle at the same time and release the brake to move forward. The engine momentum you are so fond of with the heavy flywheel is not relevant with an automatic.

    The usual choice of automatic for the 225 in a CJ-5 is the TH350. It's fairly short, which is a major consideration. Your rear driveshaft is short, and you do not have room for a long automatic transmission. Start by reading the Novak site about the TH350 and CJs. You will need an adapter to your transfer case.

    Depending on how tall your tires are, you should be able to drive faster than 55. It will be loud, but the 225 is just fine at those speeds for as long as you can stay behind the wheel.

    Why are you not considering the Warn overdrive? It works really well with the 4.88 axles and will drop your highway RPM by 25%.
     
  8. Dec 30, 2015
    B_hester

    B_hester Member

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    That's a great thought daryl! I think that would be a great route! The reason I don't want to repair the t86aa then install the OD is because that's a lot of money to put into a not very durable tranny! Plus I figured it would be convenient with an automatic.
     
  9. Dec 30, 2015
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    Does an adapter exist for the 200R4? You still need to adapt the transfer case to the transmission. Is a 200R4 strong enough for the 225?

    You understand what you are taking on with an automatic swap? Moving the engine forward will have side effects .... exhaust, cooling plumbing... it could be done neatly, but it will be a lot of work. With an automatic, you will want to upgrade the brakes, and a transmission cooler would be a good idea.

    You need a flexplate that works with the 225 and bolts to the 200R4 torque convertor. The 225 is external balance, so your choice of flexplates may be limited. A flexplate exists for the TH350 since that combination came in cars, but re the 200R4 I don't know. Research needed.

    If you want a more durable transmission, a T-15 would be a significant upgrade. A truck 4-speed would be even stronger, but more to do to make it fit.

    You know that you can use the T-90 gears in a T-86 case, as long as you replace everything? Lots of support for the T-90 in the aftermarket.
     
  10. Dec 30, 2015
    B_hester

    B_hester Member

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    So if I switch it to flex plate will it still run corrwctly? I know they made the flywheel heavy to balance it, so is the lighter flex plate going to be equally balanced? And similar low end torque?
     
  11. Dec 30, 2015
    oddfirejeeper

    oddfirejeeper Active Member

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    "I don't want to repair the t86aa then install the OD is because that's a lot of money to put into a not very durable tranny!" well if the tranny lasted this long and you rebuilt it then by all means it should last that long again
     
  12. Dec 30, 2015
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    The low-end torque does not come from the flywheel. Did you understand what I posted above about driving style?

    The heavy flywheel was used to smooth out the rough idle of the odd-fire engine. The heavy flywheel has more momentum, but it actually saps power because you have to accelerate both the heavy flywheel and the Jeep. Storing momentum comes at a cost.

    With an automatic, you spin the torque convertor and all the fluid inside of it. The engine is smoothed out by that load.

    The PROPER flexplate will have balance weights to keep the engine balanced. The flywheel has the same balance, but the heavy flywheel is not needed for balance.
     
  13. Dec 30, 2015
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    My $.02-

    go with a granny low 4 speed of some description & the OD- that will take care of your low speed torque and top speed concerns. Autos have a place if you're into hard core rock crawling or have a bum clutch leg but other than that in a short wheelbase CJ you're opening up a

    [​IMG]

    H.
     
  14. Dec 30, 2015
    colojeepguy

    colojeepguy Colorado Springs 2019 Sponsor

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    Both AA and Novak list a trans/tcase adapter for a 700R4, but nobody I'm aware of makes one for the 200R4.
    If it was my Jeep I'd put an overdrive in it and either adapt a T 15 or put the T90 gears in your trans.
     
  15. Dec 30, 2015
    Keys5a

    Keys5a Sponsor

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    For what its worth, Buick had an odd-fire 231 for the first couple years after they revived the V6, maybe up to 1975 or 1976. Many of those cars had automatic transmissions, so an appropriate flexplate and converter.
    The late 1960's Jeepsters could be had with the odd-fire 225 and automatic (th400) , so there is another source for the flexplate.
    The 200R4 you are considering should be robust enough, after all, it was used in the late '80s Buick Grand Nationals with turbos.
    Personally, I would rebuild with a T90 or a 4 speed.
    - Donny
     
  16. Dec 30, 2015
    Mike C

    Mike C Member

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    The TH200 4R can be built to take 1000+ hp but the Buick Grand National was the only relative high power OEM use. And it was never in a 4x4. It has a LONG integral tail shaft housing so won't bolt up to any T-case so would require divorce mounting which is pretty much a deal killer in a Jeep Universal. I am a fan for street vehicles, as the first gear is not so steep as the TH700R4 and the OD is higher. But for an on/off-roader, the TH700 probably a better choice.

    But if it were mine, I'd be looking at doing a SM465/T18 type swap which I think is the cat's meow for a CJ.
     
  17. Dec 30, 2015
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    My Dad put the TH350 in this Jeep, but I have to admit, it's a whole lot of fun to drive and works flawlessly. I would like to put an overdrive on it though, but I'd have to get rid of the transfer case girdle.
     
  18. Dec 30, 2015
    Norcal69

    Norcal69 Out of the box thinker 2020 Sponsor 2019 Sponsor

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    Brandon,
    I'm the guy who bought the frame from you.
    You should come down to cottonwood and drive my Jeep. Once you cruise down the freeway with an O.D. you will never be the same. I regularly drive my jeep back and forth between Cottonwood and Redding, 20 miles on the freeway and don't bat@ 65-70 and don't bat an eye. Iv'e driven from Cottonwood to Eureka and back with 3 adults in the jeep plus luggage and never dropping below 55mph the whole trip. My sig lists all my jeep specs.
    Kyle
     
    Last edited: Dec 31, 2015
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  19. Dec 31, 2015
    ITLKSEZ

    ITLKSEZ Volvophilic

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    If you absolutely need an automatic and an overdrive, I'd personally go with the th350 to a D18 with a Warn OD. Reliable, available, tried and true, short-ish...

    BUT... I'd really consider a different route for the same outcome if your main goal is freeway speeds, and get a lower crawl ratio as a byproduct. Go with a T-18/SM420/SM465/NP435 granny trans and drop your axle ratios to 3.73s. Avoid OD altogether.

    Right now your crawl ratio is a measly 33.49:1.
    With an SM465 and 3.73s, your final crawl ratio would be 60.1:1.
    With that setup, your second gear would almost be identical to your current first gear, and it would be syncronized. (33.5:1 vs 32.8:1 low range, 13.6:1 vs 13.4:1 high range)
     
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  20. Dec 31, 2015
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    Mmm. Not an expert on optimizing automatics for off-road purposes, but I believe you don't need as low a crawl ratio with an automatic as you would with a manual transmission. The two-footed style means you don't have to move forward until the stall speed of the converter is reached... this is typically 1500-1800 RPM for factory converters. Plus the converter multiplies torque from the engine at stall by roughly 2:1, so in terms of torque available you have twice the reduction of a comparable geared vehicle. And, you can control your forward speed by releasing power as you need it by letting up on the brakes.

    The truck 4-speeds are great if that's the style of driving that you want. An automatic will be different, and have different trade-offs.
     

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