check with your dealer as some will say yes they do and some will say no they don't, they don't care who makes em! and some dealers won't do a gear change either, you'll probably have to get them installed somewhere besides a dealer.

 

My 82 has a 13.5 gallon tank and I only get 100 per tank of gas with my 4:10 gears but remember I have a C-4 and a worked 351w.
Since you have an O/D tranny, you should be good with either gear set you choose.

 

with 3.73's in my '88 AOD in overdrive cruising the interstate @ 70 mph in CC with AC off and windows closed on a cool overcast day in May I once drove from Richmond, VA to Englishtown, NJ and put 330 miles on my 15.5 gallon tank before I stopped for gas after I got off the Jersey Turnpike at exit 9. Still had about 1 gallon left in tank too.
hell of a lot depends on how you drive!

 

I got about 190miles to my full tank. Of course this is my first full tank of gas with the gears put in so I drove her a little harder than normal. Before the gears I could get about 240miles. A good guess is the gears took off about 40 miles from a full tank. Hope that helps.

 

thanx a lot guys!

 

Well i got a quote here in canada on a gear swap. If i have the parts supplied they said around 4-5 hours install. Sound right? $65/hr

He said i need the following parts
-ring and pinion
-pinion bearing
-crush sleave
-pinion seal

Do i get these parts from ford besides the ring and pinion? He said the parts would be pretty well ruined by the time he takes them out. Pinion seal has to be pressed out, crush sleave needs a new one to be crushed, and pinion seal just because we are already there. So its either 4.10's or 4.30's still. Havnt made my mind up yet. I want this to be my last gear swap as its kind of expensive. I will be going with ford racing for the gears.

By the way the dealer said my warrant would be void unless i got ford to install ford oem gears. 4.10's is there lowest (ford racing is considered aftermarket) But fvck the warranty.lol