I have 31 inch tires

 

4.10

 

I have a 1990 5.0 with an AOD. What gears to you have or "think" you have in your 89? Mine also came factory ordered with the tow hitch, and i believe my gears are 3.55?? but i am not entirely sure.

 

I think they are 3.55 as well. The tag has been removed so im not really sure

 

the AOD has a pretty steep OD ratio of 0.66 and because they were only behind the 302 which is kinda underpowered anyways, it really does bog the engine alot. being a weak trans i always thought it would be best to put in alot of axle gearing to take stress off the trans.

that being said 31 would be pretty decent with 4.10 gears and what most people would do. as lnog as you dont plan on going to bigger tires. if you have alot of steep hills then maybe 4.56, it would be plenty highway friendly. im just not sure on the whole governor part of the AOD but it might need to be swappedwhen using higher gear ratios

if you ever do need to have the trans rebuilt, might look at getting it built with 'wide ratio' gearset from a 4R70W. it will give it a better 1srt and 2nd gear for more torque and lowers the OD ratio to 0.70 which helps alittle bit to make the engine bog less. not to mention the 4r70w parts are stronger and its somewhat common to build an AOD with them

 

I also have an '89 5.8 swapped from C6- AOD. Still has stock gears (~3.5) and tires. At 1600, I'm about 70. It is a bit sluggish at that speed.......however, the C-6 has a 1:1 3rd (final) gear so leaving the AOD in 3rd is like still having the C-6....until speed dictates an upship. I left my gears alone as I figured I'd be doing some higher speed cruising on trips.

 

the AOD has a pretty steep OD ratio of 0.66 and because they were only behind the 302 which is kinda underpowered anyways, it really does bog the engine alot. being a weak trans i always thought it would be best to put in alot of axle gearing to take stress off the trans.

that being said 31 would be pretty decent with 4.10 gears and what most people would do. as lnog as you dont plan on going to bigger tires. if you have alot of steep hills then maybe 4.56, it would be plenty highway friendly. im just not sure on the whole governor part of the AOD but it might need to be swappedwhen using higher gear ratios

if you ever do need to have the trans rebuilt, might look at getting it built with 'wide ratio' gearset from a 4R70W. it will give it a better 1srt and 2nd gear for more torque and lowers the OD ratio to 0.70 which helps alittle bit to make the engine bog less. not to mention the 4r70w parts are stronger and its somewhat common to build an AOD with them

I do alot of highway trips too. Any idea if it Would effect speeds up to 70 going up to 4.10 or 4.56?

 

I have a new AOD from Monster that I just love this trans. I spent a few hours getting the tv cable tuned in, but once i dialed it in, it's great. I have absolutely no issue with it dropping a gear without having to mash the pedal when it comes to a hill. would think you may need to tighten your TV cable a touch, so its not lagging on you.

The increments are very small on the adjustments, at around 1/32" each, and I went back and forth 7-8 times, fine tuning it to just right, and it's a whole different truck from where it started off at.

It shifts into OD right about 48mph under normal easy acceleration, nice crisp shifts & drops a gear right when you want.

 

as i said the AOd has an OD ratio of 0.66 so you will multiply these numbers by 0.66 and that will be yuor RPM at 65mph
to do other speeds, divide the RPM by 65 and multiply it by the desired speed (such ad 75)

you will find that the RPM difference between 4.10 and 4.56 is not very much
3.55 would be 1650rpm at 65mph, 1905 at 75mph
4.10 would be 1910rpm at 65mph, 2200 at 75mph. (15% increase in torque from 3.55)
4.56 would be 2120rpm at 65mph, 2450 at 75mph. (11% increase in torque from 4.10, 28% from 3.55)

i run my F250 with 4.56 and 33s and its mild 302 and 4R70W, i kinda wish id gone 4.88 and might end up going 5.13 with 35s in the future. both my broncos use 5.13 and 37 with E4ODs

 

I would say 4.10s, I had a AOD with a built 351w and 285/70/17 and 3.73 gears and it was still sluggish in 4th. Granted its lifted as well which defiantly hurts. Instead of 4.10s I’m now putting a 460 and zf5 to make up for lack of torque.

 

Sorry, I don't get notifications timely. I wasn't ignoring your question. Seems like Kingfish answered best. I would have suggested finding a "calculator" and plugging your info into it.