Gears - 4:10 vs. 355 RPM difference.

[Directedby]

Just installed 4:10 gears. The RPM factor is minor. Maybe I should have gone with 4:56?


65 MPH
3:55 = 1950 RPM
4:10 = 2250 RPM

[Bradley G]

Hey Directedby,

Did you drive another with 4:10's first?I did not and felt the same way you posted ,after several weeks now I am glad I did not get this extreme.Give it some time and maybe It will make sense:dunno: ??
Bradley G

[stevengerard]

yeah, after a week I have just started to notice the engine reving higher then expected occasionally but man I'm still very happy with it.

[NAVCHAP]

Love the 4:30s, you can really use the revs and get into the boost, DB & NBC know that first hand. -kjs-

[FiveO]

I'd leave the 4.10's.

BillyGman has said that the 4.56's reallllly hurt overall top speed and Overall mileage. He's had a good tank here and there but the 4.10's are a good compromise between getting off the line and good overall performance on the street and highway.


Billy..am I wrong? :D

[maraudernkc]

4:10's are the all around best gear in my opinion.

[MikesMerc]

4:10's are the all around best gear in my opinion.

Ditto.

Its personal preference on whether you want to "give up" the gas mileage and highway cruise-ability to go with much more than 4.10s.

[RF Overlord]

^^^what they all said^^^

[MarauderMark]

^^^what they all said^^^


^^^^What he said..^^^^ :lol:

[William B]

my 410's are going in on tuesday....goody
if I lose a drive shaft.....it will be an adventure....spend more money!!!!

[TripleTransAm]

Just installed 4:10 gears. The RPM factor is minor. Maybe I should have gone with 4:56?


It's not about RPM. It's about torque multiplication... (okay, on the MM, it's kind of about the RPM too). Think of it this way: at every RPM in your power band, you're now putting 15.5% more torque to the rear wheels than you used to be. Downside: you'll run out of RPM faster in each gear and have to upshift earlier, but with the exception of that very narrow range where you'll be in the next higher gear with the 4.10s whereas you'd still be in a lower gear with the 3.55s, the torque supplied in each gear will still be higher at the axle.

[StevenJ]

How much should it cost between installation at buying the gear kit? Around $500 right? Also, what oil do you need to change your rear diff. oil to? I want to change to 4.10s soon.

[BUCKWHEAT]

I'm with Navchap. I've had both. Go with the 4:30's.

[Rider90]

I'm with Navchap. I've had both. Go with the 4:30's.
What is the RPM of 4.30s at 80 MPH? IIRC, 4.10s are around 2800.

[fastblackmerc]

How much should it cost between installation at buying the gear kit? Around $500 right? Also, what oil do you need to change your rear diff. oil to? I want to change to 4.10s soon.
$500.00 is in the ball park for gears + bearings + seals + oil + labor. I use 80w140Redline gear oil (3 quarts). Just make sure whatever oil you use meets the Ford spec for our limited slip rears or you may have to buy some friction modifier to add to the oil.

[Marauderman]

What is the RPM of 4.30s at 80 MPH? IIRC, 4.10s are around 2800.
I believe that number is 3,000

[TripleTransAm]

What is the RPM of 4.30s at 80 MPH? IIRC, 4.10s are around 2800.


Anytime you know the RPM for a certain speed in a certain gear, you can just divide by the old ratio and multiply by the new one.

In your question, 2800 / 4.10 x 4.30 works out to 2936 RPM.

That same road speed with the 3.55s works out to 2424 RPM, a difference of close to 400 RPM with the 4.10s, 500 with the 4.30s.

Obviously the RPM spread between the two ratios increases with speed.

[RF Overlord]

Also, what oil do you need to change your rear diff. oil to? The axle TSB kit comes with 75W-140 synthetic.

[fastblackmerc]

I use Redline 80w140. Be sure you use oil that meets the Ford spec for limited slip diff.