The AOD isn't crap but it's not too strong either, especially for what you want to do.

With the AOD and it's tall OD gear you might even want 4.10 gears but you're not going to find those in a stock F150 axle...

It's a real can of worms ain't it?

 

Tire Gear Ratio Charts not sure if this is accurate or not

 

Every one of those I've seen, the highlighted areas seemed a bit high to me. Plus like I mentioned earlier, the 302 is very lacking in low-end power.

 

Glad to hear your leaning that way. As far as the front goes I personally see little reason not to spool/lincoln lock(weld) the front. The only time the front diff matters is when the hubs are locked. This gives you the best front traction at the lowest cost. All you give up is some hassle locking and unlocking the hubs more often when transitioning to and from the road. The ideal front diff is an ARB or other switched diff, in fact some would be great in the rear to. But HUGE $$$$$$ for those. If you have to do it "right" spools are pretty cheap by comparision, cheaper then a new posi.

Turning wheels to find a posi is VERY unlikely. First there are very few if any, and second if the one you happen to turn does have a posi chances are very good it will be too worn out to be able to tell my turning the wheel.

You would very much regret changing to a C6 the loss of overdrive and lockup converter is too much of a price to pay. Much better off making a AOD stronger if it fails you.

Accurate yes it's just math, that said for you it's different, that chart assumes a manual tranny with no overdrive. Any gear ratio choice must take the overdrive into consideration. It's the final gear ratios that count not just axle ratio.

 

Great info guys Thanks! I'll update when done. LS rear 9" weld the front. Possibly lower gears. Sounds like a plan.

 

Oh just because he says it now you're all for welding the front!?! Haha just kidding. You'll want the lower gears. I had a '89 302/aod/3.55ls super cab long box and that thing had no cojones and I was running stock tries.

 

lol no it just makes sense. Don't use the front unless it's locked in. The rear would be different. Yeah the truck is definitely not overpowered but like I said it's what I have. Hopefully the exhaust will help.

 

a full exhaust with good headers will help and so will this:
ignition upgrade and timing bump (no 56K) - FSB Forums

 

very informative thanks. I'll give it a try. will the computer save the changes to timing? I guess so or people wouldn't be doing it.

 

Gear ratio math;

Your AOD has an overdrive ratio of .67:1 which is pretty darn tall. Actually REALLY tall, before I had forgotten how tall it was. With an overdrive that tall 4.11 is no problem at all for highway cruise. Looking back the last rig like yours I did a gear change on I put 4.11s in it and it was mainly a mall cruiser.

Makes me wish I had an AOD over my C6 in my daily.

Looking at that chart multiply everything by .67 so 4.11 is really 2.75.

Well shoot by the math 4.56 sounds pretty darn atractive. Gives you a 10.9 total first gear ratio compared to your current 8.5 which will give you much better accelleration, off road, and towing ability. It gives you 28% more torque at the wheels for the same amount of engine work(throttle) making it feel like you have 28% more power. Takes strain off the transmission and engine, the rig will feel 28% lighter to the transmission and engine. And you still have a 3.05 final overdrive ratio for the highway putting you around 2500RPM on the engine at 65MPH

Total first gear ratio= first gear ratio x rear end ratio, so 2.4x3.55=8.5 compared to 2.4x4.56=10.9

Final overdrive ratio = overdrive ratio x rear end ratio, so .67x4.56=3.05 compared to .67x3.55=2.37 which you have now.

Torque at the wheel is muliplied by the ratios to. So comparing 3.55 to 4.56. 4.56 divided by 3.55 is 1.28 or 28% more.

 

Did the put a gear that low in a 9" 1/2 ton and I would need the matching for the front. I didn't want to deal with 3/4 ton stuff.

 

They may have offered 4.10's in a 9inch but not 4.56's and you won't find either in a TTB stock.

 

Are you asking about the rig I put the 4.11s in?

It was a 90 bronco with a 5.0, AOD and 31" tires. A C-clip in the stock 8.8 with 3.55 LS fell out. So I installed a 9" with 4.11s and a detroit softlock. She(the owner) had to put off doing the front gears, never used 4wd anyway and moved before I could change the front gears. At the time I just took the front driveline out to keep her from messing things up.

Putting 4.56 in your truck could be a little tricky from 2 aspects. Both the same, both I need to look up unless someone wants to chime in. The carrier which is the part the ring gear bolts to can work with a certain rang of gears before you need to change carriers, what that range is for the 9" and your TTB I need to look up.

Checking my math, a 31" tire travels about 730 rotations per mile. At 65 MPH thats 47450 rotations per hour, 791 tire rotaions per minute. Muliply by the final gear ratio (ie 3.05) gives you about 2400 engine RPM at 65MPH.

The 2500RPM number in the previous post was from the chart.

 

Fantasitc write up, I'd suggest one change. The Taylor 8mm SpiroPro wires are ok but the 8.2 Thundervolts ROCK!! Going from 400-600 ohms/ft to 50 ohms/ft is a great upgrade for just a few extra bucks. With those wires and a 65k volt pertronix coil I get away with a .075 side gap plug

Yup, even 4.10 in a 9" is rare but 4.56 would only be aftermarket.

OK so no carrier split with the 9" so any carrier you can just bolt on 4.56 gears. Pretty sure your TTB is Dana 44 based so it's split would be 3.73 so any gear numarically higher then 3.73 and you need a different carrier.