Selecting a Final Drive Ratio

Discussion in 'Mustang Chit Chat' started by Midlife Crises, Jun 13, 2020.

  1. Midlife Crises

    Midlife Crises Member

    I have a full weight 2010 GT with a 2.66 first gear T56 mag. 3.73 differential gears and something over 500HP. Using 28X10.5 MT ET Drags the diff. gears need to be changed. I see 4.10s are very popular and Ford brand gears are an easy choice. On the other hand, 4.30s are doable within my RPM range and could help the car out of the hole. I have set up Ford Performance and Yukon brand gears before but nether list 4.30. Any recommendation on ratio or brand for the 8.8 will be appreciated. Please don’t tell me to change the tranny.
  2. Juice

    Juice forum member

    I would calculate the ratio bassd on your trap speed, in 4th, to just shy of redline.
    I usually just go with Ford racing brand gears. i did install a set of Summit racing "unbranded" gears, they are fine.
    RED09GT likes this.
  3. Midlife Crises

    Midlife Crises Member

    Playing with a calculator I like what I see running 4.30s. Ford Racing doesn’t offer that gear set so are there any brands to avoid?
  4. Juice

    Juice forum member

    Don't know if there is one brand to avoid.
    I was looking at the Richmond "lightened" gears to try, but since I've decided to leave the 3.73s for now.
  5. Dino Dino Bambino

    Dino Dino Bambino I have a red car

    What he said.
    Assuming you have 500rwhp and a race weight of 3750lb, I'd anticipate a 1/4 trap speed of ~126mph.
    Your 28" tires will rotate 720 revolutions per mile. At 126mph in 4th, your engine would be at 6200rpm with 4.10 axle gears, and 6500rpm with 4.30s.
  6. WNYGT5-0

    WNYGT5-0 Member

    Run the Richmond 4.30s
    You should be able to find Ford Performance 4.30s tho... here is the pet number
  7. RED09GT

    RED09GT Senior Member S197 Team Member

    I had a set of Richmond 3.73's in a fox body and they were quiet.
    I bought the rear end complete so I can't comment on the install difficulty.
  8. Midlife Crises

    Midlife Crises Member

    Thanks for the input you have offered. I will be going with 4.30s, maybe 4.33s.
  9. 07 Boss

    07 Boss Senior Member

    I've been using Richmond gears for over 30 years. Never broke one set and I have broken a lot of cars. My latest rear end (Ford 9") I had built by Strange and I'm not sure if they use their own gears or someone else's, but it's my first non-Richmond set in forever.
    Midlife Crises likes this.
  10. GriffX

    GriffX Member

    I used a Ford 3.73 gear set and had a gear noise first which disappeared within 3000 miles. Worst part in the Ford kit was the shims from Ratech, not enough thin shims, had to file some off.
  11. Midlife Crises

    Midlife Crises Member

    Got the 4:30s and an install kit. Just waiting for the Truetrac to show up.
    Dino Dino Bambino likes this.
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