pitbullman1471

Well, got my 4.11's put in today and the difference over the stock (2.73's???) is insane. The car literally jumps out of first and can easily burn-out in second. I love it except the speedometer now reads like 80mph while I'm going much slower. I imagine that there was some kind of mechanism in the old gears that is now changed with the 4.11's that is screwing up the speedo. Any suggestions?

motorman524

you need a new speedo gear.

WhiteFoxGT

Yea you need to change the speedo gear and probably the gear inside the tailshaft. Do a search and you'll find plenty of threads with the right ratios you'll need [8D]

ModularFox

yeah when you make such a drastic gear chage it will throw your speedo way off. i never bothered to get a new one, just drive with traffic.

deanzawistowski

the only reason i got ones is so i wouldnt put more miles on my tac then there should be in case i ever have to sell her

ModularFox

yeah my car reads over 200K on it lol..but oh well i dont think ill ever sell her.

pitbullman1471

Thanks guys

AdderMk2

you definitly need a new drive and driven gear, you can get them on 50resto.com

check out this link for more info
https://mustangforums.com/m_1322654/tm.htm

you need a 6 tooth drive gear and a 20 tooth driven gear to get your speedo accurate. DO NOT... and i repeat DO NOT install the 23 tooth white gear, your speedo will still be off by 6-9 mph

stangman94

so if i get gears will my speedo be messed up?

AdderMk2

yes