hey everyone,
i have a 1990 bronco with 31 inch tires and a stock 3.55 rear end. since the bronco did come with 31 inch tires, i was wondering what would be the best rear end to put in it for more power on the start. right now i dont have any power in over drive at all so i pretty much never put it in over drive unless i am coming down a moutain or soemthing so i always drive with the thing in drive. at about 70 or 75 mph i run like 3000 to 3100rpm in drive. i was thinking of a 4.10 or a 3.90
also, i put headers and true dual exhaust on the bronco and put the o2 sensor back but only on 1 side since it only has 1 o2 scensor, but it seems liek sometimes the truck has trouble figuring to run rich or lean or perfect and i was wondering if anyoen has every had this problem or might know of another reason for this problem.
thanks a lot

 

I was thinking abou t doing the same thing for my 1992 Ford F-150 302 EFI with 3.55 gears in the front and back. I was wondering if 4.11s would be a little bit better, but would that throw off anything???


Bleed Ford Blue

 

I think after 3.55, you can only get 3.73 or 4.11, unless you want to go REALLY low.

Jrock909, it will make your speedometer read faster than what your actual speed is, other than that, nothing. I think.....

 

with an 8.8 inch rear the gears could be 3.55 3.73 3.90 4.10 i just dont know which would be right or which would be too low. i mean for the people out there who have changed their rear end what size did you put in and for what size tires was it?

 

A co worker install 4.10 in a '95 F150 4x4 without any problem. The speedo wasnt off, the sensor picks up signal at ring gear. He has 31s w/ man trans. He said he couldnt fell that big of a differance.

 

You have to keep the gears matched, yes there is a 3.90 for the rear...but not for the front axle. Your only options are a 3.73 or 4.10.

Moved to the axle forum.

 

if your at 3100 at that speed why do you want to make it worse on your engine???you should have decent power right now. Id only recommend a gear change with bigger tires.

 

If he goes to a deeper gear it'll allow him to use o/d and thus drop the revs. if the gearing is too high you have no power in o/d and it'll barely maintain speed. a deeper gear will bring this power up a bit and will also bring the revs up a bit (but they'll still be lower than driving in D with the higher gear).

Justin

 

hey justin, do you have any idea what i should try? either 4:10 or 3.73 like you said, i dont have any power in overdrive and i dont need a top speed of over 100 with is rediculous in a bronco. i have 3.55 now with 31 inch tires and the stock tires where 28 inches tall. thanks for the advice

 

(i now i'm the wrong Justin, but i can help you out ) If you threw a set of 4.11's in there you'd be equivalent to a 3.54 and stock tires, right now you're equivalent to a 3.08 and stock tires. the 3.08 is a great highway gear if you have a 1:1 top gear, but with the O/D go with 4.11's. The 3.54 is a great "compromise" gear, you don't lose too much on the bottom or the top, it's a solid midrange gear. This can also vary with which motor you have. With a 302 i'd want a 4.11 equivalent gear, with a 351 a 3.7, and a 300 a 3.54 because of the different rev ranges they operate in. Sorry, if you have a bronco II and a bent 6 or something like that i can't be of much help but i'd just keep going deeper.

Justin

EDIT: I goofed, those numbers are for 33's. Drop the numbers about .25 and they'll all be correct for 31's.