Last year I put 35" tires on my 89 F150 302 AOD. It has 4:10 gears but it is WAY underpowered. I have new Edelbrock heads with 1.9/1.6" valves, along with a Comp Cam XE256H-12 going on soon that will move the power band up a few hundred RPM's. I know the 302 isn't the most desireable truck engine but it's what I have to work with. I'm thinking of changing the gears in the rear 8.8 and front D44 to either 4:56 or 4:88. Anyone using 4:56 or 4:88's? I've heard 4:88's can be weak due to the small size of the pinion gear, is this true? I'm leaning towards the 4:88's as I want to notice a significant increase in power. Any advise would be appreciated as gear swaps are a pain.
Mark

 

since you have an overdrive tranny, and 4.10 gears feel underpowered, i would go with the 4.88s to feel a boost in power.

 

All depends on what RPMs you'll have when running on the highway. The formula is:

MPH x GEAR RATIO x 336 / Tire size x OD gear ratio = RPM at the speed u put into the equation in overdrive.

 

Originally the truck had 3.55's with 29" tires. Now I have 4.10's with 35's. It equates to the equivalent of 3.40:1 with large heavy tires. If i go to 4.56's that would equate to 3.78:1. With 4.88's the equivalent would be 4.04:1. I was just wondering if anyone had any "seat of the pants" results. I am also concerned with the strength of the 4:88's but I am still leaning towards them.
Mark

 

I have 35's with 4.56 in the pumkins, snapped some teeth off the ring and pinion last month with my tired old 5.0. My 408 is going in pretty quick here and I guess I'll be going to a one ton set up out back.

If you drive 70+ mph on the freeway, you'll be sucking down the petrol like a maddog, I get about 7 mpg at 70 with the 4.56's. Running at 2400 at 70.

 

What trans do you have though.....

 

I have the E4OD, so thats running in overdrive!

But the main point I was looking for in my previous post was that I had a problem with the smaller pinion on the 4.56 gears, so you need to consider that with more HP and larger tires the 8.8 might not be your best choice for sinking your money into.

 

94F150-408
What were you doing when the R&P failed, could you tell if the pinion failed 1st? Also was it a quality gear set, do you remember the manufacturer?
I figure if i go with 4.88's I'll be spinning about 2200 rpm's at 70 mph, now I'm spinning about 1850 rpm with the 4.10's. Hopefully my MPG won't be that bad!

Mustanggt221
What gears are you running? Do you feel underpowered, even with the 5 speed?
Mark

 

i would go with either 4.56s or 4.88s

 

The first indication of a failure in the rearend was an erratic acting speedometer, when I went to change out the speed sensor in the rear end it was all chewed up. Well, I knew some much more major than the speed sensor was going on. So, I made an appointment at a shop in the bay area to only does rear-ends. I dont know what broke first? I will check with the shop that I took it to for the brand of parts. Hopefully this set will last longer than the last.