So I am making time to work on my project 36 Ford truck. Couple hours in the evenings after family stuffs over and whenever I have extra time on the weekend. When I bought the truck the po had set the drivetrain from a 1987 Lincoln MarkVII LSC in the frame and thats about how far it got. After putting the body together I figured out that the rear axle is really about 3" to wide to get the tire and wheels to fit in the back fenders. He had the LSC wheels on the back that are offset and if you put a more typical wheel on it they are past the edge of the fender. So after looking around I have decided on a Explorer rear axle. The LSC had the 200hp 5.0 roller motor in it that year with a 3.27 rear gear ratio. My plans are not to do much with the engine at this time so no big horsepower increases. I was reading some where that a better gear ratio is a good way to make a low horsepower vehicle a little peppier. The Explorer seems to have to standard ratios, 3.55 or 3.73 with the 3.73 being limited slip in most cases. Right now I have things mocked up with a 29" tall tire on the back. I am leaning towards finding a limited slip with the 3.73 ratio but the 3.55 seem to be easier to find. So with that is there any big advantage to one ratio over the other?
3.55 will serve fine. If your desire, is to 'race for pinks' or other questionable practices the taller the ratio, the quicker Out of the Gate!
Should factor in what transmission, and it's first and final ratios, to optimize your rear ratio pick.
A lot depends on how and where you are going to drive the vehicle the most. If you are just going to drive on the street, at 60mph, go 3:73 if you are going to spend a lot of time on the interstate at 75+mph go with the 3:55. Bones
What transmission are you using,and is it overdrive? Whats the OD ratio? 3:55 with a tall tire,and lots of OD ,and you could end up with a final ratio around 2:11 .
It has the AOD with a .67 overdrive. Mostly around town driving 60-70 mph. Occasionally on the interstate to go some where but probably not very often. Would like to be able to put my foot in it every now and then when I am feeling froggy.
If the trans final ratio is overdriven it won't necessarily impact the ability to accelerate from a dead stop (or from a roll). That's more related to the first and/or low gearing ratios. As has been said, without more info regarding the trans gear ratios, any advice is going to be very general and not specific to your question. Both the 3.55 and the 3.73 are good choices to help your truck feel responsive on the street with the occasional stoplight joust. Old trucks are sort of noisy by nature so the higher, numerically, your final ratio, the more you may be missing in comfort plus the economy factor on the interstates.
I am guessing that it has the standard ratios First: 2.400:1,Second: 1.467:1,Third: 1.00:1,Overdrive: 0.667:1. I used one of the calculators and it looks like its only about a 100 rpm difference between 3.55 & 3.73 for the final cruising engine rpm. Anything else I can figure for its "power band" for the 0-60? Engine will be basically stock.
The gear ratio is a straight factor in a torque calculation. Engine torque ? Call it 200 on this one 200x 2.4 ( 1st gear) = 480 480 x 3.55 = 1704 480 x 3.73 = 1790 480x 3.90 = 1872 480 x 4.11 = 1968 You might not notice 100 rpm on the highways but you’re damn sure going to notice 50 ft lbs of torque every time you take off in first gear.
Last roadster, began w/a vette 2:78 rear, had a Ranger Ford 5spd, overdrive 5th. When I changed r&p to 3:55, then it had 4 accel gears (good spread) and a level ground OD. The old, wide, or close ratio types matter here.
So with the original 3.27 gears it would have been 480 x 3.27= 1569 and if I can come up with a 3.73 it would be 1790. I think thats what I am going to look for 1st and if I cant, settle on the 3.55. With only about a 100 rpm difference on the top end it probably wont be very noticeable.
The difference in available torque between 3.55 and 3.73 is only about 5%, which is equivalent to varying the tire diameter by 1.5". But this may be academic in a light-in-the-back pick-up, maybe with traditional tire width; either ratio will probably spin the tires.
Around here the majority of exploder rear ends are 3.73 limited slip.the next most common is 4:10,,, then come the lower ones. I like them exploder 8.8s but they are probably the heaviest “passenger” flavor rear end I’ve come across. The pinion is offset quite a bit but taking that 2-7/8” out of the long tube is pretty easy.
Right, but if someone is already looking why not get some easy performance enhancer. That 5% anyone is going to get is the easiest low hanging fruit to grab.
If you have the overdrive transmission , as stated, case closed 3:73. You will definitely notice a difference in take off between a 3:55 vs 3:73. BONES
Took my little 1956 265 SBC on the freeway for the first time today. At 70mph it's showing 3,000rpm, exactly what the calculator shows for 3:55 gear (no OD). Driving newer cars with OD, it's about 500-1000 higher than what I'm used to, but I guess it was built to do it. Torque peak is actually listed at 3,600
I use an 8.8 in my 56 Ford with a 2.74 and a cruise-o-matic 3 speed and its perfect for how I use my car. A 4.10 with a .67 OD is exactly the same. A 3.55 is a 2.37 and I’m guessing some automatic down shifting on the freeways. A 3.73 is more livable at 2.49. As for being heavy mine has a lot of cast iron cut off near the ring and pinion for mounting and of course all the factory mounts on the outside. Mine has also been shortened on the one side and uses the same shorter axles. Mine also has F-150 11 by 2-1/4” drum brakes making the e brake stock.
Divide your answers by the radius of the tyre. [inches x 12] to get the force at the tyre footprint. So with 1968 ft/lbs torque [at the axle centerline] with 26" diameter tyres ,or 13" radius tyre [1968 ÷ 13] x 12 + 1816 force / thrust In a 2400 lb car it should accelerate at 0.75G [1G ÷ 2400 lbs] x 1816 = 0.7566G or 0.75G The same weight vehicle with 250 ft/lbs torque [bolt on mods] would be like this. 250 ft/lbs x 2.4 1st gear = 600 ft/lbs at the driveshaft. 600 x 4.11 = 2466 [2466 ÷ 13] x 12 = 2276 force [1G ÷ 2400 lbs] x 2276 = 0.95G acceleration or with a 3.73 rear end 600 x 3.73 = 2238 Assuming the same 26" diameter tyres we get. [2238 ÷ 13] x 12 = 2065 force [1G ÷ 2400 lbs] x 2065 = 0.85G acceleration So you can do it with MORE POWER or torque multiplication [or both]
My 36 has a ford ranger 8.8, it came with a 3:55 trac loc, because I do nothing but long range hiway stuff, I installed 2:73's in it. It's perfect, because the truck weighs 2770, it'll still haul ass enough for me, and is fantastic on the hiway.
I ended up coming across a expldr 8.8 limited slip with 3.73 gears. Since the beginning of this topic I also decided to ditch the automatic for a manual 5 speed which I have acquired. After looking on some mustang sites that run the same engine, transmission, rear axle combo it seems that with the t-5 and sbf that the 3.73 ratio was the best all around ratio.
My 3 speed has a 2.2:1 low. With the low torque 265, uphill starts are a bit more clutch slip than I'm used to with my 5 speed daily. Much as I'd like to spin it a little less at 70-75 on a long run, I don't think I'd want to go any higher than the 3:55s.
2.20 lows were typically in cars with 4.11’s or lower. Most 4-speeds low gears were in the 2.5 range for the standard issue as I remember. I had a few 2.20’s on the street and they were not all a pleasure to drive. Our latest is a 2.88 with a 3.25 rear gear and a 28” tire and it’s a pleasure to drive on the street.
Mine's really not all that bad starting out, I think the car weighs under 3,000. But my driveway is uphill to the main road, which has a 45 mph limit (meaning they are doing 60..) so you have to jump out there and floor it, that's really the only time I notice it. I drove it to the city yesterday and from stop signs and lights it's fine. Maybe if I keep it long enough and get over keeping it original I'll stick in a 4 speed (then a 327..). Kinda like the non-synchro first 3 speed though, part of the charm of the old thing.
My Dads F-100 has a 302 and the M5OD transmission. The PO had installed an 8.8 with Traction Lok, and it has a 3.73. The 302 with the five speed runs great, has wonderful power and runs out fine with P235/70R15 tires on the back. I drove it to work one day and was running 80 on the freeway and it was turning close to 3000 RPM, my first thought was, Uh Oh, that’s a lot of RPM. Then I got to thinking about it and realized how silly that thought was, that was pretty normal before O/D became the normal.
I'd say two things. First ...........Get a rear with posi no matter which ratio you choose. If you don't get a posi then you may as well not get that froggy feeling because it isn't going to hook up. Second..........Get a rear with posi etc............
Hello, We had gear ratios from 3.55 to 4.56 in our teenage 1955-58 Chevy sedans. The 3.55 seemed like the standard from the factory. But, it did little for anyone when competing with others of the same motor and power if they were running 4.11s. Luckily, the 265 motor for the 55 Chevy was stock except for chrome accessories and our friend was not into drag racing. The 3.55 was good or possibly the best for everyday driving to high school and long distance road trips. When we went 100+ miles to Laguna Beach and La Jolla in the San Diego region, the 3.55 265 55 Chevy was a nice ride. It did not over tax the driveline or set up. We knew if he ever wanted a 3.73 or 4.11 gear ratio, they were available in one of our garages or a swap could be done. The 56 Chevy post sedan had the same 265 motor, but decided that a 3.73 was right for him. Both 265 ci motors had a 4 barrel upgrade from the stock version. But, the 3.73 gave him extra power going up hill to the local high elevations of our skiing, mountains and cabin vacations. There were plenty of 3:55 gear ratios around, the 3.73 that were also available had just enough oomph to get a little better traction off of the line. The gears did not make the Chevy sedans work too hard on long drive down the coast and back. It had something more for the mountain ranges and the steep grades all over our driving areas. So that was an advantage. Jnaki Now, the comparison between 3:73 vs the 4:11 gear ratio was no contest. The 4:11 ratio was the best all around for the drags, daily driving to school and work. On the very long drives, one could hear the motor working well, but it was normally a good drive without any difficulties. When it came time to do a little acceleration, the 4:11 gears just worked better. At the drags, the 4:11 worked fine. There were some good e.t. times and comparison to the stronger 4:56 gears was evident, but not that important for the everyday driver. What got us into using the 4:56 gears was coming in second, when the other cars in the same A/Stock class that were powered the same, were winning the elimination races. Same motor horsepower, same Positraction and exhaust systems, so the difference was the inclusion of the 4:56 Postitraction gears. When we got our own complete third member with 4:56 Positraction gears, it was a weekly event to exchange the 4:11 to 4:56 on Thursday nights for the Friday/Saturday events. Our times improved and we started winning some trophies for the effort of installing the 4:56 gears. Some would say that is not a noticeable difference, but for us, it was worth the effort to do the right thing for better times and speeds. One thing that did happen, when Sunday came around and we were tired from the whole drag racing scene from Friday to Saturday. We sometimes left the 4:56 gears in place, knowing it was only 4 days to Friday. So what happened was the motor got a little more revs on normal street driving and lower speeds on the open highways on cruise night down/up the coast. The normal activity for me as a young teenager was to get the Impala ready on Thursday night and finish interchanging the complete 4:11 third member with the complete 4:56 unit. Sometimes, it was cold, windy and tiring, but for a teenager, it was just a part of being an avid hot rodder and drag racer. On Sundays, the reverse was done for normal driving to school, errands and afterschool jobs with the 4:11 gears. Would we go back to the 3:55 gears? If we were on a high speed highway for many miles of 65 to 75 mph, then yes, the 3:55 gears are for long distance driving comfort and efficiency. But, they would instantly be changed to the 4:56 gears for intense racing. YRMV
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