I removed the entire rear end out of a nearly new 1978 F150. And put it in my 77 F100. Replaced the Dana 44 with a Ford 9 inch. They both had 2:47 gears in them and as I remember the 9 inch was 31 splines. I had better gears for the Ford axle. Not for the Dana.
Of course, both of those trucks were sold new in California. It wouldn't surprise me to find gear ratios were different in the real world.
Squirrel is right, Ford made both 2.47 and 2.50 gears. 2.47 are the lowest numerically gears Ford (or anybody else that I am aware of) has for the Ford 9-inch. In OP's case, going from 4.11 to 2.47 is a huge change, 39.9% reduction to be specific. So if highway cruising rpm was for example 3000, it would now be just a hair over 1800. Like many others said, you need to supply more info to even begin to say if the change will be acceptable or even work worth a shit.
Hi everyone, I know this is a boring subject to some but to me it's a big deal. I love my 48 coupe. I've always wanted a hot rod since I was a boy and now I have one but it needs some tweaking (like the rear gear ratio). I turn to the people on the H.A.M.B. for good info, some bad info but mostly good stuff. I would love to put in a 700R but possibly too much mods for me at this time. I never could afford a hot rod ( raising 3 boys for 12 years by my self didn't help ) now their on their own and I'm 73 years old, better late then never . I just want to have a little fun with my coupe before I take the big dirt nap if you know what I mean. At this point changing the ring and pinion to a better ratio might be my best shot. I know I'm just another wanna be hot rodder but that's where I'm at. My 48 has several problems like running hot but the rear end is whats going on right now. I know I should be just sitting around the house watching football and grand kids etc. etc, but I want to cruise. I don't know a lot about hod rods but that's why I ask you for advice. I really appreciate all your help neil
Your are headed in the right direction. Follow your heart and take your kids on your rides. They will remember grandpa and his car all their lives. When I was a little boy my grand parents lived on a farm and my grandfather had a 1950 Chev sedan and truck that seemed to be about the same color. I have fond memories of sitting between my dad & grandfather in the old car & truck. It was such a privilege to sit between these good men who let me come along to town or travel over to friends or family. The fastest way to grow old is sit on the couch and do nothing. The nonsense on the news is enough to age a person faster. I look at the mirror and think that I am lucky that I don't feel as old as the guy the guy staring back at me in the mirror. Stay active and chase your dreams. On the rear end. I would look something like this and select an rpm that makes good power at a reasonable rpm for 60mph. https://www.teambuick.com/reference/calculators.php all the best GP
I don't think you will like the 2.48 with out a lockup converter. If you use it I would think about a trans temperature gauge.
The 2.47 gear was used in big Fords with big engines in the 70s, and they didn't have lock up converters, or transmission temperature gauges. It's a nice gear for cruising around, especially on the highway. 2.75 will give a little bit more pep to the acceleration, and it's also a nice gear for cruising around and great on the highway. Ford used 2.79 gears in the 8" rear in bazillions of small cars with small engines in the 60s-70s, they worked fine.
Can you go with a taller tire? That may soften up the 4.11 impact. I have a 3.89 in my car with a Muncie, 29" tires. I'm around 3200 at 70, not bad at all. You're into 3700 with the 26" tire.
Just a tad more info- I had the 350 ( 880 truck roller cam block )lower engine rebuilt ( new crank and a beefier Comp cam to install this cam you need a 2500 + stall converter, all new bearings, HD oil pump, etc. $ 4,200 the T 400 trans has a corvette 2800 stall converter, the rear tires are 26 " tall . To me it has plenty of power and it sounds healthy as hell I'd like to put a pic. on here but I'd have to get my 7 year old grand son to install it for me. Boy some of this new stuff is crazy for this old caveman
Sorry my old age is setting in and I have forgotten how to figure out the final gear ratio taking into account the rear tire circumference along with the gear ratio. Thanks Jimbo
Ford had the 2.50 in the mid 70's and it was prone to pattern noise (whine) at 55 mph. There were so many warranted they changed it up to the 2.47. I am trying to remember.. I am thinking Mopar... Had a 2.23 gear set. Sent from my Moto G Play using The H.A.M.B. mobile app
With a 2800 stall torque converter and those gears...don't think it's gonna work.. .you'll never get past the torque converter slippage and will generate a lot of transmission heat. I know that we all have gotten used to engines loping along the highway at sub 2000rpm, but engines used to turn 3000 rpm+ all day long. When equipped right they didn't do too bad for highway economy either. I had a similarly equipped 54 Olds with a 3000 stall torque converter, turbo 400, sbc 350 etc.. lived at 3200 at about 65 mph...and pulled down mid 20 mpg.
https://www.ringpinion.com/calculators/Calc_RPM.aspx At 65 mph 4.11= 3500 rpm 3.50= 3019 3.0= 2588 2.47 = 2130 With your current set up Your ideal gear ratio would be 3.50 for 65 mph Because of the 2800 converter the 2.47 would want 2nd gear, the 3.0 could probably get away with it. At 45 mph 4.11 = 2454 3.50= 2090 3.0= 1791 2.47 = 1475 4.56 = 2723 With your current set up your ideal gear ratio would be 4.56 at 45 mph Because of your converter With the 2.47 you would want to stay in second gear and most likely with a 3.0 and possibly a 3.5 ratio. The 4.11 probably can get away it. How do you drive it mostly? Most of my driving is in town for 40 mins or 20 mins to the highway and maybe 10 mins to 10 hrs on the highway then 20 mins in town and return. My daily has 180k on it and it says my average speed over those 180k is 32 mph. That average just means that 1/2 of it was higher and half of it was lower. But it's how you plan to drive it that's important. And why change the gears if you drive 65 a small percentage of total seat time ?
The 9 " rear end is a Currie with Currie leaf springs, no fill plug on the front carrier it's on the rear of housing, still don't know what year rear end is in it.
I had a late 70's Merc Grand Marquis with a 2.47 gear behind a 460. WFO it would shift out of 2nd at 90 MPH ! The guy I bought it from was an engineer at FoMoCo. He towed an Airstream all over the country with that gear.
Well I want to thank everyone for all the great information. The way I see it right now is the 2.47 rear end is too tall for around town and the 4.11 that is in it right now works great for around here. I think I will leave the 4.11 in it and just try to not take any long trips. I really like the power it has when taking off and the turbo 400 shifts perfect . Now with all your help I know what I can and shouldn't do and for right now all is OK Thank You neil
When you want to step up, get rid of that 9" and install a Quickchange. 4.12 R&P - 67 gear sets (133 ratios) between 2.19 and 7.76 4.86 R&P - 133 ratios between 2.58 and 9.14 Change gears in less time than it took to read this thread! That is all!
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