My car is partialy a long-term Science project aimed at getting good mpg. I have a 74 Duster with a 225, automatic transmission. My plan is to have the engine re-done. At the same time I would like to consider swapping out the transmission for something with overdrive (for better mileage) and I still want an automatic. Can someone tell me what the best/easiest swap would be? I don't want to buy new so I'm hoping there is something out there from the late 70's or early 80s that might work well. I did try to search this out on FABO but wasn't completely successful. Thanks so much!!
Looking for overdrive trani advice for /6, please help
- Thread starter Valveguy
- Start date
-
Good idea!
slantsixdan
=..=
There's no overdrive automatic trans that will bolt directly up to a slant-6. You can use pre-'68 truck/van/taxi parts (adaptor ring, flex plate spacer) to bolt up an A500/A518 4-speed overdrive automatic from a Dodge truck or van equipped with 3.9 V6, 5.2 or 5.9 V8, and you can build a control setup for the overdrive and torque converter lockup as shown here, but this will not address the extensive floor pan and crossmember modifications that will be needed. Even bolting one of these transmissions to a V8 (no spacer required) requires floor pan and crossmember mods, much more so for you since you're moving the transmission rearwards.
I think your money, time, and effort would be better spent putting together a good fuel injection and ignition management system rather than doing a transmission swap of this nature.
I think your money, time, and effort would be better spent putting together a good fuel injection and ignition management system rather than doing a transmission swap of this nature.
Nothing in an overdrive auto that'll mate to a slant off the shelf. It would have to be custom made. I would recommend a GM 200R4.
slantsixdan
=..=
SS, you know I'm not a kneejerk reactionary when it comes to using well-engineered parts no matter what brand of car they were originally for, but...what's second prize? Two GM 200R4s?
abodyjoe
Well-Known Member
can use a gear vendors unit on your 904
blackbomber
Raging Member
You NEED a turbo. The turbo will increase MPG more than the OD.
Sorry, I couldn't help that. I personally like the idea of the 200R4, had one in my old El Camino. Easy to find, and cheap, although I don't know squat about the conversion process.
Seriously, though, a properly done turbo can increase your MPG, but I'm not recommending it (or against). Just being a wiseguy.
Sorry, I couldn't help that. I personally like the idea of the 200R4, had one in my old El Camino. Easy to find, and cheap, although I don't know squat about the conversion process.
Seriously, though, a properly done turbo can increase your MPG, but I'm not recommending it (or against). Just being a wiseguy.
slantsixdan
=..=
Er-ruh yeah thing is, I have a hard time trusting advice from people who don't know the difference between a "conversation" and a conversion.
(from their homepage: "GET THE OVERDRIVE CONVERSATION FOR YOUR TORQUEFLITE BIG-BLOCK!")
Yeah, I once thought about this. Its probably not a bad idea at all. I wonder if the overdrive unit would have an easier installation process which would = time & money saved. Thanks for the idea, now if I could find a good used one.
Oh My! This does look cool and at the same time you could get your trani re-built, if I am understanding this correctly. Thank you for the info/idea!
LH23H2R
Well-Known Member
I've long wondered about this very "conversation" ( :shaking2: ) .
Seriously , I've thought about the concept of an overdrive behind a Slant for some years . As Dan stated , the A500 (ad seq.) conversion requires a buuuuttload of trans tunnel mods ; then there's the adaptation issue .
It'd probably be relatively easier to slap a 5 speed manual in ; however , you inquired about autos .
How would the final --the direct-- gear be figured ? Don't want to take the engine out of its peak h.p. range , so too low a numerical axle ratio , when combined with an overdriven trans gear , would absolutely kill power and economy . But , at the other end , going to a numerically high ratio may compromise peak torque .
Really , cam specs , and torque converter stall speed are other considerations as well .
Seeing that I don't completely understand all the ins-and-out and upsides-and-downsides , I really couldn't give an honest opinion .
I'm just curious as you about what it'd take to further the potential economy of the Slant , but without compromising power / torque ranges .
Seriously , I've thought about the concept of an overdrive behind a Slant for some years . As Dan stated , the A500 (ad seq.) conversion requires a buuuuttload of trans tunnel mods ; then there's the adaptation issue .
It'd probably be relatively easier to slap a 5 speed manual in ; however , you inquired about autos .
How would the final --the direct-- gear be figured ? Don't want to take the engine out of its peak h.p. range , so too low a numerical axle ratio , when combined with an overdriven trans gear , would absolutely kill power and economy . But , at the other end , going to a numerically high ratio may compromise peak torque .
Really , cam specs , and torque converter stall speed are other considerations as well .
Seeing that I don't completely understand all the ins-and-out and upsides-and-downsides , I really couldn't give an honest opinion .
I'm just curious as you about what it'd take to further the potential economy of the Slant , but without compromising power / torque ranges .
If maximum economy is the goal, emulating the manual transmission OD Feather Duster should be the jumping off point. Finding a stick shift parts car to allow you to convert your existing car to the manual overdrive A833 will probably do more for the economy than any other single thing, followed by using anything possible to lighten the overall weight. A Mustang T-5 five speed (2.95 TO 3.35 low gear) with an S10 tail grafted on would minimize any floor pan mods and be even more efficient than the 833. The Feather Duster components would be a good start (hood, deck lid, aluminum bumper reinforcements, aluminum case 4 speed, aluminum intake manifold, etc.) on dropping weight (187 pounds by factory estimate). With or without the Feather bits, use as much fiberglass as you can afford (hood, fenders, doors, deck lid, bumpers, even Lexan fabbed up instead of glass for windows), and loose the steel bumper reinforcements to get the overall weight down. Finding an aluminum block to build would save even more (good luck with that one).
If you're absolutely set on an automatic, a late lock up converter slant six transmission is probably your best automatic bet, unless you're skilled enough to take on the requisite floor pan/torsion bar crossmember mods needed, and have a butt load of cash (1500 to 2000 grand is probably a reasonable estimate, about the same as a Gear Venders add on unit) for building and adapting any kind of late OD automatic to the slant. I had a lockup automatic from a 79 D100 van until someone wanted it more than me and appropriated it, so they're out there.
Food for thought, Mopar used a 2.7 rear gear in the automatic Feathers, and a 2.9 for the OD manuals.
I would spend my efforts on making the slant itself more efficient. If you're doing this in school, maybe the resources are there to investigate modifying the slant six cylinder head combustion chambers into closed chamber heart shaped ones (like the 302 small block head) and use pistons with a high enough crown to zero deck it to get some quench. You might want to consider running the slightly longer 198 length rods to use the zero deck pistons available for them. As long as you can control detonation, the higher you can run the compression ratio, the more economical it will be. Of course, raising the compression high enough to need premium fuel is probably contra productive to reducing fuel costs. Using bigger valves in the head and/or porting, and a camshaft larger than stock would increase power output, but almost certainly cost fuel economy.
A staged Weber two barrel carburetor adapted to an aluminum super six manifold might work for induction, and a GM 4 pin HEI module adapted to the stock (rebuilt and recurved) mag pulse electronic ignition distributor has long been an accepted mod to make the ignition more efficient over on .org.
If your skill levels and resources are up to it, you might try a lightweight long ram (something up to 20") fuel injection manifold fabricated from tubing and having weld in bungs for port injectors. A low cost way into fuel injection might be to use the components from a Ford 3.8 including the EEC IV ECM and grafting it's on distributor or DIS. Various junkyard EFI components matched to a Megasquirt is another way to skin the same cat. Building a set of long primary headers (30"-32") with long collectors (16"-20") and a 2 1/2" pipe and muffler(s) would optimize the exhaust.
Above all before you turn a wrench, devour everything you can on FABO and over at slantsix.org. There's tons of expertise and experience on these boards and guys here don't mind sharing.
Get a plan, get some help, and get started.
If you're absolutely set on an automatic, a late lock up converter slant six transmission is probably your best automatic bet, unless you're skilled enough to take on the requisite floor pan/torsion bar crossmember mods needed, and have a butt load of cash (1500 to 2000 grand is probably a reasonable estimate, about the same as a Gear Venders add on unit) for building and adapting any kind of late OD automatic to the slant. I had a lockup automatic from a 79 D100 van until someone wanted it more than me and appropriated it, so they're out there.
Food for thought, Mopar used a 2.7 rear gear in the automatic Feathers, and a 2.9 for the OD manuals.
I would spend my efforts on making the slant itself more efficient. If you're doing this in school, maybe the resources are there to investigate modifying the slant six cylinder head combustion chambers into closed chamber heart shaped ones (like the 302 small block head) and use pistons with a high enough crown to zero deck it to get some quench. You might want to consider running the slightly longer 198 length rods to use the zero deck pistons available for them. As long as you can control detonation, the higher you can run the compression ratio, the more economical it will be. Of course, raising the compression high enough to need premium fuel is probably contra productive to reducing fuel costs. Using bigger valves in the head and/or porting, and a camshaft larger than stock would increase power output, but almost certainly cost fuel economy.
A staged Weber two barrel carburetor adapted to an aluminum super six manifold might work for induction, and a GM 4 pin HEI module adapted to the stock (rebuilt and recurved) mag pulse electronic ignition distributor has long been an accepted mod to make the ignition more efficient over on .org.
If your skill levels and resources are up to it, you might try a lightweight long ram (something up to 20") fuel injection manifold fabricated from tubing and having weld in bungs for port injectors. A low cost way into fuel injection might be to use the components from a Ford 3.8 including the EEC IV ECM and grafting it's on distributor or DIS. Various junkyard EFI components matched to a Megasquirt is another way to skin the same cat. Building a set of long primary headers (30"-32") with long collectors (16"-20") and a 2 1/2" pipe and muffler(s) would optimize the exhaust.
Above all before you turn a wrench, devour everything you can on FABO and over at slantsix.org. There's tons of expertise and experience on these boards and guys here don't mind sharing.
Get a plan, get some help, and get started.
ironracer1
Gearhead
I have a Feather Duster Deck-lid...
Is the deck lid for sale?
I have another question: I know they had the feather Duster/Dart Lite in 76. What, exactly, was the automatic Torqueflite transmission that was used/available for this car? Was that transmission geared differently, did it have a lower third gear? Seems like I saw something about that somewhere in FABO. If so, I wonder if there are any of those transmissions out there to be found. Does anyone know the details that I am looking for?
LOL Dan'o! I hope the guys doing the transgressions aren't the ones that do the website. (or did I mean transmissions) tmm
Dan is right, the place to start is a solid EMS with a feedback loop.
Swap the intake for a 4bbl manifold, and run a 4150 replacement EFI unit from FAST / MSD / Powerjection III, etc. Run that split 3>1 exhaust header, it scavenges well. Upgrade the ignition to a CD system of some sort.
Once you are getting power from every drop of fuel, then you can address the transmission.
There is no reason to replace the 904 with a larger, heavier unit. Go through the 904, and make sure it is working properly.
The big change is the torque converter. Things have improved a lot in 40 years. You need to drive your car and pay attention to the tachometer. Whatever you use for a torque converter needs to stall below the cruising rpm. Newer torque converters can be built to do what you want. Once you know a little about the RPM ranges you operate at, you can call someone at ACC & have them make a converter for your needs.
It might seem backwards, but you may need to raise the stall a little. A better launch from a stoplight burns less fuel if you can stay on the torque peak of the engine. It used to be that a "high stall" converter felt like the car was in neutral until you raised the RPM & it would "bite" This is no longer the case with more modern designs.
I swapped out a dead 5 speed OD trans in my pickup for a C6. With a 4.9L I6, it gets better mileage around town than it did with the manual transmission. I had ACC/ Boss Hog build a needle bearing converter for it, with a 2400 stall speed. I never changed the rear end, so it burns a little more fuel at 75 mph & above. 2 years of mileage logs tell me it has saved me hundreds in fuel costs.
B.
Swap the intake for a 4bbl manifold, and run a 4150 replacement EFI unit from FAST / MSD / Powerjection III, etc. Run that split 3>1 exhaust header, it scavenges well. Upgrade the ignition to a CD system of some sort.
Once you are getting power from every drop of fuel, then you can address the transmission.
There is no reason to replace the 904 with a larger, heavier unit. Go through the 904, and make sure it is working properly.
The big change is the torque converter. Things have improved a lot in 40 years. You need to drive your car and pay attention to the tachometer. Whatever you use for a torque converter needs to stall below the cruising rpm. Newer torque converters can be built to do what you want. Once you know a little about the RPM ranges you operate at, you can call someone at ACC & have them make a converter for your needs.
It might seem backwards, but you may need to raise the stall a little. A better launch from a stoplight burns less fuel if you can stay on the torque peak of the engine. It used to be that a "high stall" converter felt like the car was in neutral until you raised the RPM & it would "bite" This is no longer the case with more modern designs.
I swapped out a dead 5 speed OD trans in my pickup for a C6. With a 4.9L I6, it gets better mileage around town than it did with the manual transmission. I had ACC/ Boss Hog build a needle bearing converter for it, with a 2400 stall speed. I never changed the rear end, so it burns a little more fuel at 75 mph & above. 2 years of mileage logs tell me it has saved me hundreds in fuel costs.
B.
6pakattack
Well-Known Member
Here you go !!
http://smrtrans.tripod.com/smrtransmissionsintro/id20.html
I'm having a 727 w/Gear Vendors OD unit built for my /6 project !!!
http://smrtrans.tripod.com/smrtransmissionsintro/id20.html
I'm having a 727 w/Gear Vendors OD unit built for my /6 project !!!
slantsixdan
=..=
16mpg with a 4bbl setup driven as though you're a grandma going to church is quite good. You'd do quite a bit better with a more realistically/sensibly-chosen carburetor and intake manifold, such as a well-chosen 2bbl setup.
It's sounding more and more to me like you have a great deal of adjusting and repairing to do before you can establish a realistic baseline from which to improve your fuel economy. That's if you're really doing a science project and have lots of money and time to spend on upgrading and re-engineering one thing at a time and carefully recording the effect on economy and performance.
If what you really meant was that you want your car to give better fuel economy, then all this talk about fuel injection and overdrive transmissions and turbochargers and such should be put on hold for the time being. What indications do you have that the engine is whipped or that the transmission is due for replacement?
As quickly as you can, get the three books described in this thread and start reading.
Yes. And since you're running a Clifford intake without provisions for manifold heat, that's reducing your fuel mileage, too. And what's the exhaust setup? Not a stock manifold, which is open at the top where there's a connection to a stock or Offenhauser or Weiand intake, but not to the Clifford. What do you have, headers or something? What other modifications have been made to this engine/car?
Don't see why. Beware: feature creep kills projects (and bank accounts) dead!
Wow, this is just what I have been looking to see and I'm glad to see someone that is doing it! What is the vehickle that this is going into and how soon is all of this going down? Good luck, I'll be watching!
Yes, I have the Clifford headers, dual exhaust. (the exhaust system has an annoyingly loud, howl between 45 and 60 mph) I bought the car about six years ago and the odometer said 97000 and was disconnected. There was not much of any history given to me about the vehicle. Its burning a little oil, leeks a little oil from the oil pan and needs a motor mount badly all of which, I have been told, can only be repaired by by pulling the engine. Nothing else has really been done to the engine except that I also have a complete supersix set-up sitting in a large box in my garage from a 1978 donar car waiting for?? I have heard mixed reviews from many people here about whether I should keep the Clifford or go for the SuperSix. I'm not anywhere near the league you mechanics are in but I'm dying to learn! I do not have that much money to work with which is why I'm going slow AND asking you guys for help so that I don't have to do this twice. Thank you Slantsixdan!!
-
