Technical Ford 200 six final gear question

Hi all,hope everyones doing good. Heres a fun question concerning rear axle ratio.Heres the drivetrain so far. A ford 200cid straight six with a factory 3 spd toploader transmission. Ok, so,, I got a good deal on a ford 9" which turns out to be from a 75 torino.I know this is not an ideal lineup ,but am working with what I have. I would like to find a rear differential ratio that would let me drive on the highway and keep the rpms down. What ratios are available for 9" that would even do that? The tag was missing from the differential so Im guessing its stock.

 

Lots of options commonly available, from 2.73-4.56. The right one depends on the weight of the car and your expectations of acceleration. IMO, assuming a low 3000s weight with a 220ci engine, anything under 3.50 isn't going to feel good in traffic.

 

you can count turns to figure out what ratio the rear is now. Count the number of times the pinion yoke turns, for each time that both axles turn one turn each (or one stays still, and the other turns two turns--it all adds up the same). The number of turns of the pinion is the ratio.

I would expect it would have 2.75 or 3.00 gears in it, but might be something else.

I also expect that 3.50 is going to be a good ratio for your car, if you like it to accelerate a bit. But if the rear has a lower number gear ratio, you can try it and see if you like it. You'll do fine for highway RPM with 2.75 gears, but might not be so happy with how it gets moving.

 

My brothers 70 f-100 has a 240 six, three on the tree, and a 3.70:1 9 inch under it. It drives ok on the backroads around here, but I think it could use a little more gear myself. I don’t know how weight and tire size compare to what your building, but it’s a data point.

 

What vehicle is this going in? If it is off-topic for this board, don't say, just give the vehicle weight.

Also, what is your rear tire size?

 

Everything here is relative.

A typical stock Falcon or Mustang with this engine would have had something around 3.50:1 gears, as @squirrel rightly recommends.

Those cars were not all that heavy, and the tires were kinda short.

Keeping the RPMs low on the highway is not always the best thing to do with these engines, and in many cases, any carbureted engine. The lower the velocity of air through the carburetor, the poorer the fuel metering.

This might actually harm your mileage, rather than improve it. It will certainly harm your off-the-line acceleration.

When I first got my '60 Falcon, it had original height tires, and a stock 144, with all of about 90-hp, and if I remember correctly, 3.56:1 rear gears. It got 32mpg on the highway.

Now, it has 2" taller tires, and a 200, with 199-hp (crank), and 5.13:1 rear gears. Of course, it also has a T-56 6-speed, with a 0.50:1 6th, which makes for an equivalent final drive of about 2.56:1. If it still had a carburetor, it would likely not function on the highway, at-all. It now gets 34mpg, and can be at the speed limit, by the end of the entrance ramp.

 

1975 Torino axle ratios were 2.75, 3.00, 3.25, 3.40, 3.55:1. Keep in mind, a 1975 Torino would have had a 351, 400, or a 460 to turn those gears.

Count your rotations, as previously instructed, carefully, as most of these ratios are pretty close to each other.

Available Ford 9" ratios range from 2.50:1 - 7.33:1, with about 30-steps in-between.

 

They went down to 2.47 in the late 70s. Fun gears, with a big motor in a light car. No need for OD.

 

A buddy of mine had an 81 f-150 with 300 six and 4 spd OD trans and complained about how he couldn't use OD unless he was on flat ground or downhill even the slightest uphill required downshift.Put it up on a lift to check rear gear ratio and found a 2.26 or 2.29 gear ratio in it,so they went at least that low.

 

Not sure what you are building... but from my experiences the little 6 does best when reved up.

Initially I build my 3900 pound f1 with a stock 200, 3 speed, 3.50 gears and 29 inch tall tires... the revs where down on the highway but I was unable to maintain 70mph unless I was going downhill or on the flat. And even then I had the throttle floored the whole time. And was constantly downshifting to go up hills.

Well I wanted to go to larger 750-16 tires which did and it was terrible. I had to use the low range of tge transfercase just to pull put on a hill if I had a load on the truck. So I decided to rehear the axles to 4.56.. which was a massive improvement.. the rpms are up over 3000 on the highway, but I dont have to floor it all the time and dont have to downshift... it is a joy to drive.

I have since built up the 200 with flat tios for high compression as well as a custom cam.. runs great. 185,000 miles later I am redoing the body now so it will last another 20 years of winter driving.

 

A 3.00 to 1 gear was fords bread and butter set for a 200cid six, I had one of many 60s Fords that had a 3.55, a 66 Fairlane wagon.
It's difficult to find a gear deeper than 3.25 for the 8" rear axle found in the Fairlane. The only 3.25s I have had were behind the 170 cid six.

 

An F1 would not have had a 200, unless someone swapped it in there. The 200 is in a different engine family.

The 200 is the evolution of the Falcon-6, introduced in 1960.

 

Totally different engine.

 

Yeah I'm quite aware of that since they never used the falcon six in trucks except for the falcon pickup,I was just pointing out that they had 9" gear ratios as low as 2.26 or 2.29.I suppose if you had actually read other posts ,instead of skimming to see if you could find possible mistakes to point out you would have realized that.

 

never seen a 9" ratio beyond 2.47. But they did have them in other rears.

 

Yeah I thought the same as you that 2.47 was the lowest,until I pulled that 3rd member to replace it with a 3.25.I couldn't believe that they would combine that ratio with an overdrive trans,in the 50's and 60's overdrive tansmission meant steeper rear gears.

 

My stock bought new 65 Comet with 200 6L, 4spd Dagenham and factory 3.20 rear gear gave many a 300hp boat a good run up to about 60 mph, top end of 3rd gear, about 4500 rpm. 3rd [1.31?] overall ratio was about 4.25. Car weighed 2770 [I think]. So maybe 4.11 rear and t5z 5spd would be fun. 2.79 overall in 5th.

 

I read all of them.

I am pointing out that you are making misleading comparisons.

And they used the Falcon-6 in the Bronco.

 

I made no comparison misleading or otherwise,but you are making misleading statements in that the first generation Bronco was not a truck it was a utility vehicle,unlike the Chevy Blazer it was not a variation of the truck chassis until the second generation Bronco came out in 1978.You'd think that as a California licensed and bonded Vehicle Verifier you would know that.

 

Cool story, bro.

 

It appears that what was originally proposed as a "fun question" has degenerated into virtual fisticuffs!

I'm kinda dumb; I have no idea what the following expressions mean:
"steeper rear gear"...."under a 3:50"....."a little more gear"....."deeper than 3:25"....."ratio beyond 2:47"....."2:47 was the lowest"
Sometimes I can figure it out by the context, but not always. I wish there were a single one-syllable word that meant "ratio of a larger numerical value" to avoid having to say all that.

I don't see any responses that comment on the irrationality of this rear end swap. Unless the ultimate plan is to install a high performance 460, the 9" is a massive overkill. Furthermore it is much heavier, has a 63.2" track vs the Falcon's 56 to 58", has a 5 lugs rather than 4 of most (all?) Falcons, has the wrong spring pad locations, will destroy the proper front-to-rear brake bias ratio, would likely require driveshaft alterations, and for all we know might have the same axle ratio. I suspect it would be far cheaper to install a 4 or 5 speed transmission with overdrive high gear. I don't know Falcons that well, but I assume there's a stock 200 bell housing that would mate to such a transmission.

There should be a moratorium on responding to this, unless the OP posts the ratios of his two axles, and states any planned engine changes, and his priorities for acceleration vs cruising rpm vs gas mileage.

To provide some guidance:

• Acceration rate will vary directly with the numerical value of ratio change. If you lower the value 20% (say from 3.0 to 2.4), time to 60mph will increase 20%.
• Obviously, the cruising rpm will decrease 20% at a given speed.
• The time to go a given distance from a standing start will increase as the inverse of the square root of the ratio change, i.e., decreasing 20% to 80% would increase the e.t. by the square root of 1/.8, = 1.118; or, the car would be 11.8% slower.

The above are approximations, ignoring air resistance and whether one gear ratio would require an additional shift in accelerating. Highway top speed would not be increased by the same 20%, as air resistance becomes the dominant variable. Horsepower required increases as the cube of the speed; if it took 100 hp to go 100, it would take 133 hp to go 110.

 

I think his choice on the 9" was more on availability than need,it is overkill for a mild 200 but except for the fact that it does absorb a little more power than other types of rears there really is no downside,plus as you pointed out if he later decides to upgrade with more power he's good to go.Your absolutely right on the terms used to describe ratio's being confusing that's why I try to avoid the terms lower and higher,because depending on whether your describing,numerical value or speed capability they are opposite.Swapping a transmission such as a T-5 is doable but depending on the year of the 200 (bellhousing bolt pattern)it can get pretty difficult.If its an early 200 with the small bellhousing bolt pattern (early 60's) the bells are tougher to adapt due to the peanut trans bolt pattern.Late 60's vintage 200's with the big bolt pattern will accept a bellhousing with the 65-later toploader style trans. bolt pattern which is much easier to adapt to a T-5.While there have been several references to the 200 falcon 6 the OP never did specify that the car is a Falcon,if it is a falcon he's working on your right the torino axle will be way too wide.

 

I swapped it in when I did the 4x4 conversion



Also note that ford used like 3 diferent bellhousings on this engine!!!!! I found that out the hard way!!

 

Bronco parts?

Did you do anything with the carburetor and distributor?

 

Yes I used a bronco tranny and t-case. I modified an early bronco Dana 44 housing for the front as well.....using diferent outers.

The carb is a stock Holley from the 70s.... I vaigly remember messing with the advance some in the duraspark distributorwhen I built up the motor... and not using the vacume advance.

 

Sounds like a good combo.

 

Did the block's bell housing bolt pattern change from "small" to "big" coincident with the change to 7 main bearings? Did the "big" pattern stay the same for the 250? And was this the same as the 240/300 big blocks (which was the same as the V8's)?

You're right, I was presumptuous to assume the engine was in a Falcon. But I have trouble imagining this engine being considered in the build of a non-Falcon rod. Having a single intake port doesn't really say "performance potential" to me. If you mill the side off the head and adapt 3 carbs or fuel injection, as the midget racers used to do, I'd become interested. Or fit an Aussie cross-flow head (although someone told me that the blocks might be different too). If one wanted a small inline push-rod 6, and wasn't hung up on country of origin, I'd suggest a Triumph or Volvo B30, with 4-speed (plus overdrive if you wish).

 

The biggest thing you need to do is sell the 3 speed transmission and replace it with some form of small 5 speed. Short of doing that, any result you get will be limited and disappointing. The 9" is overkill and unless its already the correct width and has a ratio reasonably close to what you need,narrowing and changing ratios could be more expensive than buying a rear with the correct width. You can sell that rear for more than many rear ends will cost you. Maybe an S10, a ranger or an 8" Ford. It would be sheer luck if the 9" is the perfect width for your project.

 

Never used one, but I always liked the BW T50, for it's compactness and looks. Has regular Chevy bolt pattern. Was used in Monzas and its several GM siblings, with some small V8s, and in the Cosworth Vega. I'd also investigate a Mazda Miata, Volvo OD, or any of several Japanese units. The older Volvos had an iron case and looked more agricultural, if a real "traditional" look is preferred, but that's probably not a requirement if attached to a Falcon.

 

Des,the the small and big bell 200 should really be referred to as small and smallest 1 was for a 9 inch clutch flywheel and the other for a 9.5 or 10" cluch flywheel and ford moved the bolt pattern just enough to accommodate it,why they just didn't make it the same as the 250 and the big 6 and sbf v-8 escapes me especially since that was done only a couple of years before the 250 came out.I don't know if it coincided with 7 main,I do know that there was 1 more variation of the 200 block in the late 70's-early 80's when it was used in the newly released fox body mustang and Fairmont,they moved the starter from a high mount to a low mount,don't know if that was the same as the 250 or sbf though.The big 6 (240/300) used the same bell pattern as the sbf from the get go in 65 as did the 250 in 69.I agree about the cast in manifold,back in the day Ford/Autolite marketed a kit to mount 2 additional carbs by holesawing or boring 2 additional holes in the top and installing ubolted adaptors to mount the carbs.Another Aussie setup prior to the crossflow was the 2V which still used a non crossflow head with a bolt on aluminum intake manifold from the factory.This setup is the easiest to adapt to US falcon 6 shortblocks it essentially is bolt on,while the crossflow setup is not so easy it by far has the highest potential.I also question the choice,but it is a great economical and reliable engine and not bad looking especially with tripower kit installed.