axle gear ratio and lift ques.
 

I have a 78 F-150 4x4 with a 4" lift and soon to be 35" tires. I cannot decide between 4.10 and 4.56 gears. I currently have 3.50. Can someone with 35's tell me what they have and what they think of them. Im worried that if I go 4.10 I wont be happy with the power, and with 4.56's my engine (351) will be running too high of rpm's (like around 3000) on the highway and my gas mileage will go way down. What should I go with.

Also, I went with a 4" rough country lift becuase it was the cheapest and after I put it on I began to hear that they are notorious for sagging. Is this true. Last thing - my 4" lift lifted the truck 3.5" in front and 5" in back (new leaf springs) I want to level it out by putting 6" skyjacker springs in front. Is there anything wrong with this idea. It has degreed c-bushings and dropped pitman arm and dropped track bar aleady. Sorry for the long questions. Thanks for any replies.

axle gear ratio and lift ques.
 

Hi Nick,
I have a 79 with 35's and was in the same position as you. Stock 3.50's, I really wanted something in the 4.30 range-cannot do with the reverse cut 44 in the front. I found a guy with 35's and 4.56's and went for a ride with him, at 60 mph he is turning almost 3 grand. I like to run highway to go off-road up north and usually cruise about 65-70 mph, 351's will turn the r's but this seemed just a little much for me(351M with 400 crank & pistons) as far as bottom end, with 4.10's I have no problems makin' the rears scream on the pavement, and turn about 2900 rpm's at 70 or so. I also do not haul anything except a pair of full size spares and rather large tool/parts boxes, and 40 gal. of go juice. The engine has quite an array of aftermarket parts(headers, cam, roller rockers, intake , 4 bbl, ignition, ect, ect.) so I do have somewhat more power than in stock trim. The 4.10's work just fine, much more power than I had when I had 33's and 3.50's. If you don't do any cruisin' above 60 the 4.56's will be better off-road, you will lose fuel mileage when cruisin' but may gain this back around town. Also if you tow/haul heavy loads the 4.56's will be much better. As far as lift goes, I have about 3.5" in the front and just custom spring packs in the rear to almost level the truck with full tank and other stuff that I carry. This was to try and get more weight over the rear tires and balance the truck(It's level with about 1/4 tank). The only thing you might have to do with 6" coils is drop the radius arm brackets by about 3" give or take a little, otherwise the front suspension will not have much droop, and will be hard on bushings. Hope this little bit helps you with makin' your choice. Chuck P.
79 150 4x4 stepside 351M, C-6, NP205

One other note, the auto provides some slip, so the gearing can be a little less steep than in a manual trans. Also for auto's A-1 makes kits to lower 1st gear by 11% and 2nd by 5%-with this installed your 4.10's will act like 4.56's in first gear. These are a little salty though, to the tune of about $500 for the complete kit! I'll wait til rebuild time!

axle gear ratio and lift ques.
 

As long as you do not plan to go any larger with your tires the 4.10 gears are probably enough. I run 36 and 38 inch tires on my 91 F250, 4.10:1 gears and a supercharged 460. There is plenty of power but I can not even use OD on any kind of incline due to the wear and tear on the torque converter. With 35' tires, 4.10:1 gear ratio, and no overdrive, you should be turning about 2820 RPMs at 70 MPH. With the 4.56 gear ratio you will be turning about 3130 RPMs.If you plan on doing a lot of 4 wheelin though,you would probably be happier with the 4.56. I have thought about gearing my F250 to 4.56 except that I compete with it in Mud Boggs and with the 4.10 ratio it alows me to leave the line in 4 WD Low and still have enough speed at the finish. Its more of a matter of what you want the truck to do best when complete.Off road you cant go wrong with the 4.56 gears,especialy if you install a locker in at least the rear end,(I preffer the rear locked,and the front limited slip),but you still have to be happy with it on the Hwy. As far as suspension goes,I think the previouse response is right on the mark.
Jeff

axle gear ratio and lift ques.
 

for achart you can refer to go to this web address:
www.tennessee4x4.com/trailrunners/techinfo/gear-ratio-guide.htm

axle gear ratio and lift ques.
 

So this post has been dead for almost 9 years.....and its funny cause its the same kind of post we'd expect today....

You dug this up why? Yeah to much extra time on your hands. Better get a new project

naa thats a good post the guy gave all his info the first try and did get mad when someone told him what they thought was the best. and no one chimed in a said youd be fine with the 3.50s

WHY?


WHY WOULD YOU FIND THIS POST?
Dont you have a home...or friends...or a pet...?

My new sig quote!

lol...i wanted to see how long back this forum went.....it went back to when i got my first car....

Somtimes its best to leave the horse buried.

Let it die......

:eek: I run 35's on my 6cyl 5-speed with 3.55's with no probs. I just use low-range off-road :eek:

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