I have a 1991 Mustang Gt 5.0L with an AOD automatic i recently put in a set of 4.10's only to find out that there was not a speedometer gear to match. any ideas on how to get my speedo to read correctly??

 

your options are limited. and don't be discouraged, 4.10's are the only way to go in a 5.0 that does not have a blower. i use 4.10's in my 5-speed cars.

anyways, to correctly fix a speedo in a fox w/ 4.10's you need a 6 tooth drive gear and 20t driven gear, but an aod has the drive gear machined on the output shaft.
so you can get a 23t driven gear (which is a jeep part, not a mustang part, it has the wrong pitch to the teeth, it will wear eventually but you to about 10% eror)
and thats all you can do.

like i said, it's worth it trust me....you would have been dissapointed w/ 3.73's, i owned 2 aod cars w/ 3.73's and after the first i swore i'd never do it again.

 

What's so bad about the 3.73s? I just got mine and I like them. I only stepped up from 3.27 (stock) but I still feel the difference.

 

nothing, he just prefers 4.10s

i went to 3.55s from my 3.08 and also noticed a pretty big diff. My friend had 4.10s in his '03GT and it was just too much gear for my personal taste.

 

i owned 2 cars w/ 3.73's and stepped up from 3.27 as well on the first.

yes there was a difference, but i preferred more. even w/ the low gearset , and tci 2200 converter the car didn't leave hard enuff.

if you want to race at all, 4.10's are the perfect gear , you will run through the traps at about 5000 rpm.

you want a total 1st gear of at LEAST 9.00 or greater , (3.73 X 2.40 = 8.952 ) (4.10 X 2.40 = 9.84 )

to put tht in perspective....... a 5-speed in 2nd gear w/ 4.10's = 8.159

 

4.10s might be the way to go to race, but for a daily driver your RPMs and gas milage would be crappy. What are your RPMs at 60-70 in a 5spd with 4.10s?

 

yea a 20 tooth driven gear would work if i had a 7 tooth tailshaft but in 1991 the aod transmissions had an 8 tooth gear machined onto the tailshaft so the 20 tooth gear would be nearly 20 percent off


anyone else have any idea's are any speedo correction boxes mad for automatics? i kno they make them for manuals.

 

as do most of the people, and i assume your buddy was an auto?