I Have an 86 F150 302 W/AOD EFI 6"lift and 33"muds, 175000 original miles extended cab. now my question is I plan to tow a toy box with my truck, I have no idea what is in there know but I know it won't tow that great. Will be towing up and down hills thru mountains to glamis. I do like to drive 80mph so what gear do i get? 3.73,4.11,4.86. I think my stock gear is 2.75? Also it is a 9" rear end right?

I found some geas on Ebay not a bad prices I found 4.11,4.86 richmond gears. another thing spline? what? do I need one of these also?

I'm pretty lost so any help is good help.

Tony

 

You can find a lot of info here. If your rear diff bolts in from the front of the axle, it's a 9". If it has a sheet-metal cover bolted to the back, it's an 8.8".

 

O.K. i looked at my truck standing at the rear of the truck it has 10 bolts to remove. on the drivers door panel under axel it has #19. does any of this help?

tony

 

#19 Should be an 8.8" 3.55 open diff. It may feel like a 2.75 with 33's.

Try 4.10's for towing. Your gas mileage may suffer, but you have an AOD, so that'll help some. If you want a good gear for mixed driving (light towing/ commuting) and better gas mileage without the trailer, the 3.73 will work, but will lag on hilly terrain.

Hope that will help.

-Kerry

 

Great info I think I will go 3.73. when it gets to hilly I can just take it out of OD right?


So I have a 8.8 rear end? I just wnat to make sure before I buy the new gears. Sorry to ask again..

Oh I also have the long bed so does that make a difference?

 

You have the 8.8", since you have the rear differential cover (the 10 bolt heads can be seen from the bumper) and the 3.55 ratio. The long bed makes for somewhat heavier truck and more likely to affect aero dynamics with the bed/ front of trailer. The 4.10's just sound like a better match.

To figure what the best ratio would be for you application I would keep several things in mind.
-You should never tow with the auto in OD (you can get away with it for so long, then wear and tear takes its toll).
-How often am I going to tow with it?
-How heavy is the trailer?
-Do I care what my gas mileage is without towing (it's a truck, the gas mileage shouldn't matter to you, IMHO)?
-What type of terrain is it going to see on a regular basis?
-Do I care if grandma passes me as I climb and the tranny downshifts to 2nd?
-What is the optimum power band for this engine and tranny combo?
It'll take you some research and question asking... that's what these boards are for.

You know the answer (or at least a rough guestimate) to most of these questions already. The one that's tricky is the powerband of the engine/tranny. If you gear it too high (numerically lower) it'll be a dog towing anything. With that in mind I would tend toward the 4.10's..even with OD off unless you've upgraded the 302 and AOD considerably (more torque/ horsies and tranny upgrade to handle it) or have a really light trailer (less than 1000 lbs loaded). The 33's and trailer will lower the engine speed while the gears make up for them. Also, if you haven't done it already, try our trailer towing board.

-Kerry

 

Wow that was great info........ 4.10 is the winner.

I will be towing a toybox with a quad inside.

so I'm going to get this done asap and I will let you know how it goes thanks again....

tony

 

Be sure to correct your speedo- Did you correct it when you went from stock size to 33's?

 

no I did not but it is about 5 mph off so i don't worry about it but when I get it geared i will take it in to get done.

How hard is it to re gear anyway?

 

The time and price depends on whether you have a 4X or not. A couple of hours per (if they aren't new and know the operation) and the price of gears (good brand names will cost you, but I've heard horror stories about the cheap stuff). Around the boards I've seen anywhre from $500 to several thousand bucks. Depends, again, on the place and setup you put in.

While they've got it up in the air, tell them to correct your ODO/Speedo gear. It's a plastic gear in either the tranny or xfer case. Shouldn't take them long to change it out and match the gears/tires.

-Kerry

 

I have seen some gears from richmond 3.73,3.76,4.11 for around $100.00-150.00.

If I go out and buy them myself and put them in, well how hard to put in?

remove the 10 bolts drain out fluid and............pull out gear and pinon replace geard and pinon bolt back up fill fluid proably with a pump? also new gasket?

Do you need to remove the tires to remove the axel to get to the gears?

bottom line someone with some mechanical exp. can do?

thanks for the info.

tony

 

It's not that simple. The gears have to be set-up for mesh and backlash.

 

so basically take it to a professional?