I've always been of the mind that for OD you'd want around a 3.73 gear or bettter, depending on tire size..it might lug and buck with 3.23s....but only one way to find out!
Our 2003 Mustang Cobra came from the factory with a 3.55 rear end ratio and a .63 transmission ratio in 6th gear of the 6 speed manual. That is a final drive ratio of 2.24. That is very close to the final drive ratio of 2.26 using a 4L6E .7 overdrive and 3.23 rear end gears. The Mustang will cruise at 2250 RPMs at 75 MPH on 26 inch tires. That is a nice gas saving and engine saving over time. If a little 281 CI V8 in a 4000 lb convertible can do it, I would not worry about lugging a big 401 with lots of torque. You will just need to tune for it. The 3.06 first gear ratio of the 4L60E will also be nice combining for a 9.88 overall ratio with the 3.23 rear end ratio. That should help get it moving along well from a start on the street without the unmanagable race car tire spin of the 11+ overall first gear ratios. Cheryl
the money for a computer controller and a built 60e wouldn't be to cheap and idk what you gain over a non electric trans really. 700r4 or 200-4r wouldn't hurt the pocket book as much and would perform as good for the most part. plus 600 bucks or more still in your pocket. the x frame may be tight with a 700r4/60e. im not sure there ive never owned a x frame car. the 200-4r is a bit shorter than the 60e variants if so.
I would target a cruise rpm of 2400 rpm's or slightly more. It's unfair to compare cubic inches and rpms assuming knowing a part throttle torque curve between an engine with greater avg. piston speed and a very long intake runner intended to boost torque in such a low rpm range (4.6) to a bigger one having a slower avg. piston speed and shorter intake runners that's intended to cruise at a slightly higher rpm, especially in a vehicle likely 1000lbs greater and quite possibly much less aerodynamic. (sorry for that sentence!) The emphasis on aero and weight requiring the part throttle torque to be greater by an exponential amount (when talking about 70-75 mph). Torque curves and cubic inch comparisons matter more at WOT. At part throttle the above factors outweigh that. If you err to SLIGHTLY more rpm's you will not likely lug the engine, and you may hurt mileage a negligible amount...if any. If the rpms get too low requiring a much wider throttle opening, you begin losing vaporization, combustion efficiency, etc....mileage quickly suffers. It's rare to get engines this size (shorter stroke) to do well in the 1800-2000 rpm range (at 75 mph) without close attention to tuning or a much lighter vehicle.
Actually the piston speeds are quite similar as the stroke is only .09" different ( 3.64" vs 3.55"). The 401 runners are also longer due to direct entry to the 4.6 heads from the open SC plenum. Top speeds in stock form are close to 160 mph: meaning down force requirements have more effect on aero and may have more drag then the 59 of speculation. Weights may also be similar due to safety and emissions requirements on newer cars. So, my contention is a that we have some facts about the comparison before spouting off with information. Cheryl
Oh, my point wasn't to challenge you Babeola! I'm simply suggesting that there's more to it than cubes, weight, and rpms, esp. when picking hot rod parts out of a catalog and having a local machine shop cut to nominal rebuilder specs. My suggestions were to get the OP to think about that along with a recommendation to err towards slightly more rpms, to minimize risks of building a turd. Without putting the engines under the microscope or measuring things the average enthusiast cannot measure (or even consider), there are still differences. Shipping weight on the 59 is 4500 and I'm guessing 5000 rolling down the road with a couple of people and junk in the trunk. We are talking drag at 70-75, not lbs of down force @ 160. I'd be willing to bet there are huge differences in CD in a wind tunnel. You got me on the rod ratio's, 1.67 to 1.70 from memory? We haven't even addressed MCSA, velocity , mixture motion, delta p (on both sides of the intake valve) across the powerband (all at part throttle no less). etc. There's going to be differences. Nobody is being paid to engineer this guy's project, that's why there's generalizations. I'm basing my suggestion to lean towards a few more R's coming from the viewpoint of long having proven exceptional mileage with full sized cars (with much bigger engines). I didn't get any of them there by always lowering cruise rpms... The OP doesn't have to take mine or anyone's advice. I appreciate that this is an information sharing forum and always enjoy the contributions here!
401 or 425 w/ ST400and 300 converter, ported heads and manifolds 1966 q-jet manifold BBB1972 Q-jet 3.23 posi gears, tall tires cruise sweet spot at 65MPH nice mileage.
Still no facts or anything close to proof of concept. Seems like a log wined way to say you don't have a clue, but try this. BTW-Downforce and drag are directly and mathematically related. Cheryl
Regardless, does anyone have any other input as to whether or not this setup ( Big Body Buick, 4L Trans, and 3.23 rear) will present me with any major operational woes? "Lugging" seems to be thrown around a lot on other posts I've read. Is that a legitimate concern for me? I'm sure someone has used a 4L on a Nailhead in a bigger boat like my own...
You could drive around in 3rd. gear for most normal driving. Just make sure the converter locks up in 3rd. When on the highway doing 75-80+ you could then use OD. Seems like a waste of time & money to me just for the use of OD. I feel, like others, that a switch-pitch TH400 would serve you fine. Even though the "Nail" is a low RPM torque producer too low a cruise RPM is no good either & defeats the purpose of OD. JMHO Tom T.
I have to agree with Rhett and Tom on this one. If you are only planning on running 3.23 gears, then save yourself some money and a bunch of headache and run a ST400. Has the correct bell housing, so no need for an adapter. You will pick up the switch pitch torque converter features which are nice on the Nailhead for drivability and performance. Also no electronics to hook-up and no T/V cable to mess with. It's just simpler and works just as well. With a ST400, 3.23 gears, running 225-70R14 tires, you can run 70 mph at just under 3,000 RPMs. I'd say that's highway enough. I plan to have the same setup except to run 3.36 or 3.42 gears. With 3.42's it would be a 65 mph cruise at the same RPM. I don't plan to make super long trips, so I can deal with the little slower highway for better low end performance. But to each their own. Yes it can be done. Not sure of who has done it. I know people have done 700R4's and maybe the 200-4R, but can't think of anyone who has done a Nailhead 4L80 off the top of my head. Good Luck with whichever you decide.
If you rebuild that nailhead correctly and carefully with quality modern components (don't even think of using NOS piston rings), service regularly with good oil, you will never wear it out in your lifetime. Always have it balanced. I recently changed the cylinder heads on my 55 Century (machine shop screw up) at 80,000 miles and the cylinders still had hone marks. It runs strong and quiet. This car is used for 2-4K mile cross country trips at 70-75 mph; 3.41 rear gears. The car will be more enjoyable with a non overdrive and/or lockup transmission because you will have better throttle response at all speeds and engine braking. Another good way to screw up driveability is to install a non-stock cam that shifts the hp and torque curve a few hundred rpm higher without going to at least 3.9 gears.
i for one don't think the car will be bad at all with a od and 323 gears. 9c1 caprices had the same gearing and a 700 or 60e depending on year and they had no issue even back when they had tbi or carbs.
The Electra I have has a 3.23 posi with a 400 turbo and switch pitch. It's more than adequate at normal highway speeds. Go over 70 and the car starts to get hairy to handle. The only time it was inadequate was on the Coquilhalla Highway in BC. I wanted to lope along at 70, and soon found that I was in the way. Next thing I knew I was doing 85-90 and that car was a fight to hang on to in the corners. It also used $120 worth of gas to do about 200 miles. It pretty much ran with the 4 barrels open all the way. What follows is just my opinion gleaned from running big Buicks for 30 years, I'm sure the experts here will tell me I'm all wet, they usually do, so take it for what it's worth. So the long and the short of it is that you can build a powertrain with an OD and do the speeds, but you still are limited by the handling. There is next to no way you can make that 2 ton boat handle as well as a late model Roadmaster wagon, the layout and balance of everything is just wrong. So IMHO you will only be able to do 60-70 safely, and depending on how efficient that motor is running, it may still use a ton of fuel. It'll burn what it needs, regardless of RPM or speed, the design is pretty limited. The Nail needs to "fly" in order to breathe; otherwise it's stifled and half-dead. It's actually a better mate for the Twin Turbine than it is for the TH 400. If you want effortless loping, then get a BBB on an OD transmission; they have the torque to do anything.
I have been weighing out everyones different opinions, experiences, and suggestions regarding 3.23 gears and OD Trans.. Provided I end up going the 4L Overdrive route, Is there a way to "Lock Up" the Convertor in 3rd or keep the trans in 3rd? Just in case The overdrive gear is too much, inducing this lugging effect..? I like the lower 1st and 2nd gear of the 4L opposed to the gearing on the TH-400 or SP-400. Thats another reason I keep leaning towards it. Lower gears, AND overdrive. I just clearly don't want to "Build a Turd" if at all possible hahaa.
The modern automatic overdrive transmissions are programmed against going into overdrive unless a certain speed and lack of load are present. Similarly they are programmed to unlock and downshift when in overdrive and loads are increased. They use inputs of load, line pressure, temperature and speed to to name a few in determining these shift points. The parameters for these inputs can be modified with the aftermarket controllers available. This means you can control the shift points within a range of these inputs. The other thing to note is that the 4l80e and 4l60e overdrive drums are designed to be very light and small with minimal frictions. This improves efficiency in overdrive, but makes it in no way able to withstand any wide open throttle or heavy loads. Having had the 4l80e for our Suburban apart, I would say a motorcycle clutch would have more holding power then the OD clutch assembly. The overdrive unit is just there to move the car along at part throttle under a light load and get out of the way during heavier acceleration or greater loads. So, you have to keep in mind that you will not be able to accelerate very much or face steeper grades in overdrive before it will shift down. Mainly, overdrive will be used to maintain speed on the highway at a lower RPM on relatively flat land. I have one last example of for you. My parents have a late 90s Jimmy came stock with a 4.3 6 cylinder engine and 4l60e with 3.73 gears and 31" tires. Its GVW is over 5000 pounds and it must have similar brick-like aerodynamics as your 59. The 31" tires and 3.73 gears work out to a similar ratio as a 3.23 with 26" tires. Like our Suburban, the Jimmy drops down from OD as soon as you step on it, as Ed would say, assertively or if you head up anything more then a subtle grade. My hope is this helps framing your expectations for the OD trans when making your decision. Cheryl
Unless I'm sorely mistaken, Downshifting in the situations you laid out seem desirable. Again, unless I'm missing something or misunderstanding...
Nope, not missing anything at all. Some people expect overdrive to be Superdrive. I just wanted to make sure you understood it is not, and that the downshift prevents "turd" behavior. Cheryl
you could make it handle as well as any modern truck though there balance is horrible and ive been to triple numbers in one of them. the setup is very similar just stiffing up the suspension and decent tires would make one not dart all over.
My experience with B and C body cars has been different than Marc's-some Wildcats an Electra and even a '73 Catalina are all great road cars. I like the perimeter frame for this better than the X as with the E bodies. My Riv is some better after I replaced somewhat sloppy track bar bushings, but still not as nice as the others. I really like 'road gears' as I'm not a stoplight racer and 2.56/2.73/3.07 fill the bill. My 430-455 engines certainly do breath better than the nailhead, but I give longevity to the nail.
