NoSlow5oh

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??

nitrous_bob

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.

samseed101

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.

OnyxCobra

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.

nitrous_bob

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

WhiteFoxGT

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?

NoSlow5oh

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.

mustangman02232

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