i have a question for ya'll i have a 66 f100 custom cab camper special i put a FT 391 HD in it with a granny 4 speed and it has a Dana 60.2 or 60.3 with 4.10 gears but when i'm driving 65mph that's around 3000 rpm so it sucks more gas than it should i have plenty power to spare since my motor makes its most grunt on the lower end of the rpm range and i have not been able to find an overdrive style trans to put in so im stuck with the choice of finding a new ring and pinion set for this strange rear end which the highest gears i have found for it are 3.54s but thats around $400-$500 or dropping this rear out and sliding in one of my 9"s which gives me a larger and cheaper inventory of parts should i keep the Dana or go 9" whats your opinions? whats the tallest gear for a 9"? thanks guys

 

Why the hello is that setup in a half ton pickup? How do you use this truck?

I have a 2.75 9" set, so I know they go to that.



John

 

TALLEST 9 inch: 2.47-1 = 1977/78 LTD/Grand Marquis.

 

[QUOTE=jowilker;12221676]Why the hello is that setup in a half ton pickup? How do you use this truck?

it was an option apparently it originally had a 352 in it but it developed a taste for eating dizzy's and cams so i found a 391 hd in an old f700 that belonged to a feed store that had been laid over on its side motor had only 30,000 miles on it since it was only used seasonally i bought it for $400 shoved her in with it i can pull any load i have ever been able to hook on to ive moved trailer houses and haul scrap with my tandem axle trailer my record was a 18,000 lb load not including truck and trailer had to use gears because brakes didn't like the load lol who would of thought right lol but other then that i use it for a daily driver and showing off doing burnouts and cutting donuts (this truck will do one on one side of a two lane and give me change to boot lol) i treat my girls rough but i always give them the best when it comes to parts

 

i just called randy's ring and pinion and richmond yesterday and both told me the tallest gear available for the 60.2/.3 is the 3.54, and that is what i have in my truck. good luck to you brother, im swapping my axle soon.

 

Smokin, No offense, but you have got to go one way or the other. That setup aint gonna sip gas, & melt tires too. The 391 is a pulling engine so mpgs aint gonna play no how. A compromise will have to be arranged.

Unless I start on dirt or brake lock it mine aint gonna leave any rubber. Tires cost too damn much for that anyways, plus they are getting harder to find with all the 16s, 17s, & 18s out.

A local near me has a Lincoln 4.6 & auto OD in his Slick that will render 22-23, but these old boys are all heavy drinkers.

If you want to keep the engine, & get mpgs, you have to get way towards 2000 rpms @ 60 mph.





John

 

i was over at my brother in laws house finishing up his mud truck and we got to talking and browsing his stockpile and he has an 80's model with a dana 44 with 3.08 gears so i think with a little fab work i will be able to get it under my truck measurements are a little wider but not bad enough to interfere with my bed i am gonna have to relocate bracket the springs and pin set on though.... but on the plus side i also traded some things and got a 4x4 frame for my 72 (my picture to the left) it has a dana 44 with 4.10s in it so i can throw my 60.2 under it so that will make me happier not having to abandon a good rearend (sorry about to ramble) by my calculations at 2000 rpm 58 mph with 3.08 where with the 4.10 2000 rpm was 42 mph so a gain of 16 mph sounds like a small upgrade so i gain 1247ft per minute using same amount of gas so my 12 mpg should gain at least 3mpg if i could ever find a t-85 with the .80 overdrive at 2000 rpm theoretically 68 mph from 2000 rpm with the 3.08 gears (but of course all this doesn't factor in wind and drag coefficient) and that would be a gain of 26 mph at 2000 rpm and gain a grand total of 1496 feet per minute which translates to a gain of an additional 3.4 mpg so all together without facing aerodynamic problems i would gain 6.4 mpg 18.4 mpg at 68 mph instead of 12 mpg at 50 mph(my personal best gas mileage and speed in this truck)and also mean i could travel 102 miles further per full gas tank and have almost a 300 mile trip per gas tank but that is in a world without variables and we live in a world that this probably wouldn't happen but a fella could always hope right (sorry i'm rambling)