Gears for the Bronco

[Ozwynn]

I bought a set of Ford Motorsport 4.56 gears for the 8.8 in Bronco and a set of USA standard 4.56 for the 44 in the front.

after reviewing some things I am wondering if 4.10 or 4.30 would be better

33" tires and a .71 OD

4.56= 1813 RPMs @ 55 mph, 2143 @ 65, and 2308 @ 70 (this is close to what the minivan is geared at)

4.30= 1710 @ 55, 2021 @ 65, 2176 @ 70

4.10= 1630 @ 55, 1927 @ 65, 2075 @ 70

3.90= 1551 @ 55, 1833 @ 65, 1974 @ 70 (recommended for keeping factory performance.... factory performance caused all kinds of transmission problems)

the torque on the 351 peaks around 2800. Its primary function is to be a daily driver/winter beater/ and week end warrior...... not insane off roader.

I do like the fact that 4.56 leaves room for future upgrade to 35s where the others don't and out of all of them the 4.56 would lend to a cooler running transmission therefore a longer lasting transmission.

what I am trying to figure out is what is a decent cruising RPM for 55 - 70 mph. Are the 4.56 going to work for me......

 

[847alexc]

I had a 92 bronc myself. Though, your post said you have a 351 while your profile states a 5.0L (302). If you do indeed have a 5.0 (as I did) you will find that those rpm numbers will be higher to accommodate the lower torque output. When I was putting gears in my truck I looked into this issue as well (though my budget forced me to eventually not change ratios in the end).

Ford stated an ideal cruising rpm of around 2200 rpm. You are right, the stock gears are too conservative (likely 3.54 right now, eh). I suspect that the 4.54 gears will be overly aggressive if you plan on using this as a daily driver. really, the 4.10 gears will be plenty, 4.30 some to spare. the 4.54 gears will take you outside of the cruising range.

All of this of course assumes you are running an OD trans, hopefully the HD E4OD trans, and not the AOD. the C6 was also installed in trucks up to 91, though they are only 3-speeds

you can spin anything up to 44's on a stock 8.8 setup (by strength rating), if you have enough power. I would have to say that you could still upgrade to 35's with either the 4.10 or 4.30 gears.

I can see you have put the right kind of thought into this, and I leave you with my two cents.

One last thought... With all of the gear and tire changes, don't forget to reprogram the speed sensor. Not having that correctly adjusted (especially for the E4OD) can fry a trans much faster that regular wear. You can actually reprogram the computer without any special tools up to 3 times (at least that was the case for thed 92-up). though I had to get the procedure for that off of a dealership computer. I think I have the details in my garage somewhere if you need the info.

anyways, good luck

 

[Ozwynn]

I currently have a 302 in the truck. I have a roller cammed 351 from a 97 F250 going in as the 302 died a week after i bought it. I do have the E4OD, 91 had a transmission mounted VSS and a spur gear driven cable speedo. I have to change the spur gear and that takes care of the VSS. The 92+ were MAF and a bit more complicated that what I got.

still not sure on the gears. I can take my 4.56 back and get 4.30 and save $50 on the 8.8 set but I would spend that on the front set because the only 4.30 I can find are FMS gears.

I can get a 44 3rd and an 8.8 rear already set up if I go with 4.09/4.10


[EDIT] I was wrong, i have to swap in a D50 3rd to get 4.30 gears for the front [/EDIT]