What options for O/D behind a S/6?

Transmission and Drivetrain Tech

  1. dodgedartgt

    dodgedartgt Well-Known Member

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    We are anxious awaiting delivery of my daughter's (first car) '62 Valiant Signet 2dr H/T. We have a good 225 coming with it, ready for install.

    I plan on installing an A500 in my '67 'cuda, but am curious what options there are to put O/D behind her S/6. I actually have an aluminum case 4 spd O/D from a low miles Feather Duster, but she REALLY wants to keep the push button shifter. I'm aware that Imperial Services makes an adapter cable set to connect button shifters to newer lever style transmissions.

    Any ideas? I'm not above having an A500 forward case machined down and doing something like the UltraBell conversion to put an A518 behind a big block. I was thinking of using a S/6 bellhousing and custom adapter plate.

    Thnx, Mike in FL
     
  2. MuuMuu101

    MuuMuu101 Well-Known Member

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  3. jbc426

    jbc426 Well-Known Member

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    Be prepared to do this then. Snip, snip, cut, fabricate something then weld and weld some more. Slant six's are generally tuned pretty poorly for performance, so trying to drive a Mopar overdrive with one will really tax it. They take more power to drive than almost anything else. They're not known for their efficiency.

    Gear Vendors are kind of like halfway to overdrive with driveline clunks and vibrations. Splitting gears from 1l, 1h, 2l, 2hm 3l 3h is very hard to do well. Almost impossible for the average guy, so don't put too much stock into that drag strip dreaming fallacy.
     

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  4. Tbone416

    Tbone416 Well-Known Member

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    It mite be possible to use a A500RH out of a 4 banger Dakota. I have seen other post were member's have use the 6/ banger trans on a 2.4 Dakota power plant.
     
  5. rumblefish360

    rumblefish360 So close, yet so far away

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    Now that is an interesting thought.

    Being the slant 6 has a unique bell housing, what would be the odds of installing another maker of a manual trans onto it?
     
  6. dodgedartgt

    dodgedartgt Well-Known Member

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    Hi guys,

    Trust me, this doesn't have anything to do with drag racing. And a Gear Vendors unit is twice the budget of the purchase of the car itself!

    I just wan't to 1) maximize fuel economy, and 2) take advantage of a lower 1st gear ratio for quicker pick-up. There is no reason that this car shouldn't have a solid 30mpg all around.

    The Valiant won't take very tall tires. I learned driving the 'cuda cross country last week, that even with the 2.76 gears I put in, it was still turning about 2500 in cruise because of the (only) 24" tall 215/60/14's on it and converter slip. I only averaged 16.5-17mpg with a best tank of 18mpg. I'd hate to think what it would have been if I'd left the 3.91's in for the 3300 mile drive... sheesh!

    I know the trans cross member, and maybe the tunnel itself will require surgery to use an A500.

    I know that some 8-1/4's had 2.45's and even 2.2's (different carrier required?), but I don't want to sacrifice what little acceleration the car is going to have. An A500, with its 0.69 O/D ratio would give 3.55's an effective ratio of 2.45... 3.23's would become 2.23 in O/D.

    Does the 200R4 or any others have a divorced bellhousing? IIRC, the 200R4 is single wire lock-up.

    Whatever trans I use, it won't need any performance mods to hold up behind a snarling '74 S/6, LOL!!!

    More suggestions?

    Thnx, Mike in FL
     
  7. jbc426

    jbc426 Well-Known Member

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    My 7 + years of Slant 6 experience taught me that it gets the same mileage as a EFI 5.9 Magnum if you stay off the throttle on both. I'm building a factory computer EFI reflashed for a 408" motor hooked to a beefed up 200R4 with a lock-up torque converter and 3.91 rear end gears. I expect it will get in the high teens if not low 20 mpg at 60 - 65 mph. If I swapped in a slanty in place of the 408"r, it would do about the same.

    I got 18 mpg at 70 mph with a well-worn 5.9 Magnum with a small cam and headers and a non-lock-up 727 with 3.23's going from Willow Springs to Burbank for Spring Fling. That was the best I ever got. My Slant came close, but never reached that good of mileage and it had a 904 & 2.97's or something in that range.

    Bottom line, the slant ran a 19 second 1/4 mile and got slightly less mileage that a worn 5.9 Magnum that would do mid 13's in the 1/4 and still get 16 average on the highway without overdrive. I never got good gas mileage with my slant 6 for the sacrifice you give up in power when you want or need it. Do yourself a favor and swap in a junkyard EFI 5.9 Magnum, bolted up to a 727 or a 200R4 and then you will have the best of both worlds.

    I know my slant liked LOTS of initial timing. I had it set at 22 initial and 32 total. The vacuum advance was hooked to manifold vacuum and it really ran at it's best when set there.
     
  8. Woods74

    Woods74 Broke Senior

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    ^Yup, I've experienced the same phenomenon. Got better MPG with 250 more HP/TQ with a spread bore carb. No brainier.
     
  9. nm9stheham

    nm9stheham Well-Known Member

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    Youse guys are doin' something wrong. I had a '76 Dart Lite that got 27-28 mpg at 70+ mph and 29 mpg at 65 mph. I think that car had a 2.76 rear. Al lthe 225 cars my family had without OD's (2 autos and 2 3-speed manuals) got in the 22-24 range on the interstate.

    Probably won't be able to make it work, but the old Hone-O-Drive is back: http://hone-o-drive.com/

    If you have no use for that 4 speed OD Feather Duster trannie, please let me know!
     
  10. jbc426

    jbc426 Well-Known Member

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    Those feather Dusters cars were developed to get that kind of mileage during the gas crunch when the Arabs were pissed off that we supported the Israelis during the six day war, and cut us off from the crude oil spigot.

    I talked to Doug Dutra at length about this subject, and he often had similar results but did say he has a few cars that got 3 or 4 mpg more than I did on some of his slanty's. That puts the mileage up near where you were. I be the were pretty slow off the line if they did pull down 22 to 24 mpg. The feather Dusters were in a class of their own with the special overdrive and all.
     
  11. dodgedartgt

    dodgedartgt Well-Known Member

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    nm9s - No use ??? Yeah, sure. Don't even think about it! LOL :glasses7:

    This would be a piece of cake it my daughter would have a clutch. The 5spd out of 1st generation 4 cylinder Dakota trucks will bolt to a S/6 4spd bellhousing with just the addition of 'tabs' for the lower bolt holes.

    Mike in FL
     
  12. moperformance

    moperformance Well-Known Member

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    My daughter and I pulled everything out of a full sized PU w/6. the aluminium 4 spd (3 speed w/od) has been in for 8 years. I had to re-clock the Z-bar but everything fit in her 73 Dart. A body peddle assemblies are easy enough to convert. With a new clutch kit we had less than $200 in it. She loves rowing through the gears ;D
     
  13. TylerW

    TylerW Well-Known Member

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    The 6 cylinder vs. V8 mpg comparison is true. You really don't get a free lunch with a small engine. If you drive it with an egg under your foot, you'll get good mileage. If you drive it in order to keep up with modern traffic, you won't. There is just simply not enough power and you will be in the throttle so much your mileage will be out the window.

    That's like a buddy that had one of the first Nissan frontier trucks, a 1998 Xtra cab 4wd with a 4cyl. Not only was it severely underpowered, but highway mileage was about 16mpg at 70 mpg, simply because it had to work so hard. With a 4cyl!

    My suggestion would be to scrap the slant idea and put a V8 in it. You'll be quite happy with it.
     
  14. barbee6043

    barbee6043 barbee 6043 FABO Gold Member

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    lots of arguments on here bout slant mileage. I've had them: feather duster auto ( yes they made them), 70-3 dusters, 4 speed OD, autos, old engines, rebuilt ones, all country driving ( not trying to stay alive on the Ca freeway!!) the non feather car, 4 spd OD got 30 ( true), the feather with well used engine got around 25, others got low 20's.
    personally, I've grown to like the oddball slants, yea I still love any V8 too!!!
    for some reason, some of us like the goofy typewriter pushbutton!!?? LOL
     
  15. MoparDaddy

    MoparDaddy Damn Right I Carry!

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    I would just put a 318/OD in it with GM TBI and HEI conversion. She will have all the acceleration she need with the efficiency of the efi and be as easy to work on as having a carburetor. With that, there's no reason not to see 25-28mpg on the hwy and about 18-20 in town.
     
  16. nm9stheham

    nm9stheham Well-Known Member

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    No, that Nissan got poorer mileage because it is like a cinder block moving through air. The wind resistance loads were high, and the higher rev's increasing the pumping and internal friction losses. It was a bad combo for that use.

    Yes, you do get a free lunch with a smaller engine: it is called lower pumping losses. This load factor can be lower if the RPM's are lowered with any engine (i.e. OD), but also go down with displacment. That is the main reason for my '09 Challenger getting 25 mpg in the Appalachian interstates' the 0.5 OD in 6th drops the engine RPMS to lower the pumping losses (plus rotating losses like the cam loads). You gotta be willing to look at the whole package of load factors to figure it out: wind resistance load, RPM's and displacement for pumping loss loads, drivetrain losses, rolling resistance losses, etc.

    I had no need to drive my Darts' with an egg under my foot to get the mileages that I did. I DO have a steady foot however, which might be a difference in results. But I could beat on that Dart Lite in particular and still get good mileages in the mid's 20's roaring around in the mtns here. The manual trannie (vs a slush box with non-locking TC) helped I am sure. No way 318 would not have a done that.

    My bottom line point is that 16-18 mpg in a Dart /6 at 70 mph is low; something is being driven wrong or there is a carb tuning or other issue. With a 2.76 rear gear at interstate speeds, the engine is in a 'happy' (efficient) RPM range.

    I think this may encapsulate what is different: "I talked to Doug Dutra at length about this subject, and he often had similar results but did say he has a few cars that got 3 or 4 mpg more than I did on some of his slanty's. That puts the mileage up near where you were. I be the were pretty slow off the line if they did pull down 22 to 24 mpg." jbc426 states that he put a lot of advance into his /6's; OK for best track time, not OK for best mileage.

    So which does everyone want: 22-24 mpg or best track times? If 16-18 mpg is OK, then by all means go with a V8; I pulled 17-19 mpg all day long in the interstate with a 351C Ranchero that would blow off every stock 440 R/T type Mopars that it came up against..but to get to the 22-24 range, I would have needed a serious overdrive. Not so with a plain-jane /6 w/o OD.
     
  17. dodgedartgt

    dodgedartgt Well-Known Member

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    At this point, a non S/6 swap is NOT an option. FWIW, I average 20-22 mpg in my 4400 lb '93 Dakota with 3.9l / AX15 5spd / 3.21 8-1/4" and cruise control. And it weighs a WHOLE lot more than the Valiant. Currently only looking at S/6 O/D options, I have a strong 40k miles 225, with A/C components already installed. Also a40ish k miles 3.9l saved from a destroyed van body due to how well it ran, again with a/c components installed. Either engine coupled with a '62 dealer installed underdash A/C unit fixes any FL specific short coming we may have to overcome with this car.

    Mike in FL
     
  18. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Personally I believe this entire discussion resembles using a space shuttle to go roller skating. There is no easy or cheap AUTO OD unit than will be cheap enough to ever recoup the install cost vs the small increase in mileage it "might" give you at least in the case of a slant in a light body

    If you don't want to put an OD A833 in it, I'd leave the thing alone. Put your money into Decent Tires and a Really Good Tuneup. Examine the rear axle ratio, but I'd bet you won't improve on that
     
  19. YY1

    YY1 Well-Known Member

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    How about a lockup trans?
     
  20. dodgedartgt

    dodgedartgt Well-Known Member

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    Good idea. Was there a lock-up S/6 trans option? What years, etc?

    Mike in FL
     
  21. inkjunkie

    inkjunkie Well-Known Member

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    You best hope a certain Gear Vendor lover never sees this, he will rip you a new one....Have to wonder if a / has enough torque to warrant an od trans? Our 99 Exploder with a 4.0 SOHC with 200k miles on it is starting to struggle with staying locked up in od and then often times just staying in od. Our car is set op for a 4l80e, the torsion bar cross member needed to go. Keep in mind that the t-bars twist, so once the rigidity is gone you will have problems. There are ways to deal with it, just hunt for the thread by the fellow that swapped a t-56 into his car and made a very beefy looking brace to replace what he cut out. Or you could just swap in a HE or AlterK....

    An auto OD & cost efficient, in an A-body at least, is sort of an oxy-moron....best of luck to you....
     
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    • Powerflite

      Powerflite Well-Known Member

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      I am thinking of the same possibilities. Is it possible to convert a /6 trans to use 999/998 trans guts? Or else, how possible would it be to get a 999 to bolt up to a /6? I assume that these transmissions have small V8 bolt patterns. Is there an adapter? That would at least get you:

      1. Lockup converter
      2. Lower 1st, 2nd gears
      3. Option to bolt up a gear vendor overdrive

      I believe a 999/998 has physically the same outer dimensions as the 904.
       
    • lildemonkid

      lildemonkid Well-Known Member

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      IMHO i have a big 4 barrel (390 dual feed double pumper) with headers on my 225 slant and i get 20 to 22mpg hwy running premium(93) in mine.(ethanol in modern gas affects mileage big time) the biggest thing is tuning the carb and timing just right. once thats done the 904 and a stock slant can easily get close to 30mpg. if you want the best fuel economy put a 4spd behind it.

      Set the gap larger on the plugs
      tune the carb as best as possible
      3.23 gears (best accel and mileage combo)
      free up the exhaust
      adjust the valves
      pertronix points to electronic conversion
      decent ignition coil.

      All in about 200 unless you put a different rear end in it.
       
    • Supershafts

      Supershafts Well-Known Member

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      Well i could always take one for a ride and ask for ones excuse when the nonsense spewed doesn't happen...

      Honestly though in his defense, i agree, 94% of the population really can't drive, and im willing to bet thats the case here too
       
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