Anyone Using 3.90 Gears??

[LakeShoreDriver]

I know this topic has been beaten to death,,, but on a Mustang forum I found Americanmuscle.com. They have a 3.90 gear by Motive Performance for the Ford 8.8" diff. advertised for all Mustangs and as a popular compromise between the 3.55 and 4.10. I do 90% of my MM driving at 75-80 mph and would rather not wind up that motor for that long at those speeds with a 4.10. Anyone know about this company Motive Performance?
Anyone using these???

[fastblackmerc]

The difference between the stock 3.55's and 3.90's is negligible. IMHO, you'll be wasting your money. The 4.10's increase engine RPM's by about 200 at speed, not enough to do any damage. Go with the 4.10's, you'll be glad you did.

[BruteForce]

Get 4:56 ratio. Then you can be cool like Brute. :coolman:

[Bradley G]

You're not gonna notice much difference between them.
I would go with Ford Racing gears they have been good .
I got 50K on mine and no noise.

[Raudermaster]

It's been discussed here before, 4.10's are the best bang for the buck and you'll notice a big difference with them.

[SC Cheesehead]

The difference between the stock 3.55's and 3.90's is negligible. IMHO, you'll be wasting your money. The 4.10's increase engine RPM's by about 200 at speed, not enough to do any damage. Go with the 4.10's, you'll be glad you did.


^^^^^^^ what Jim said ^^^^^^

With the O/D engaged, the engine's going to be running 2,300 - 2,400 rpm 70-75 mph. I've found the car to actually perform better at highway speed with 4:10's as it's running up a bit further in the power curve. Impact on gas mileage is minimal.

SCCH

[Joe Walsh]

I know this topic has been beaten to death,,, but on a Mustang forum I found Americanmuscle.com. They have a 3.90 gear by Motive Performance for the Ford 8.8" diff. advertised for all Mustangs and as a popular compromise between the 3.55 and 4.10. I do 90% of my MM driving at 75-80 mph and would rather not wind up that motor for that long at those speeds with a 4.10. Anyone know about this company Motive Performance?
Anyone using these???

I am......or I should say......I will.

When I drive my Marauder, most of the driving is on the highway, so I really didn't want to go to the 4.10s.
I'm actually pretty happy with the OEM 3.55s but I do want more acceleration.:D
I knew that the 3.73s are not worth the effort because of the small change from the OEM 3.55s.
I bought a set of Motive 3.90s gears and will be installing them when I remove my rear axle for a total build*.
I've had the 3.90 gearset Cryo-Rem treated so they require no break-in and will be bullet proof.
www.evansperformance.com

*( Motive 3.90s, Detroit Truetrac, 31 spline axles, welded axle tubes, ARP stud kit/billet caps & SVO aluminum cover w/preload screws)

I think that the 3.90s will be a great for the Marauder.

[magindat]

www.magindat.net/ssm/info/4r70wratios.xls (http://www.mercurymarauder.net/forums/www.magindat.net/ssm/info/4r70wratios.xls)

Enter the values, see the differences. Make your choice.

BTW, stock revs/mile for the tires is 724.

[Stranger in the Black Sedan]

I self-installed 3.73 gears. I think 3.90s would be perfect in this car. 4.10 is too much gear for a big luxo barge in my opinion. Cryo treated gears? Unless you are putting tons and tons of HP through them, that was a waste of $$. Gears are not going to wear out just highway cruising/daily driving.

[GreekGod]

The choice of rear tires (and their rolling radius) can negate any difference between a 3.90 and a 4.10 ratio...if you want to split hairs, tire choice must be accounted for, also..the difference between the gear choice really amounts to a quality & price comparison.

[Krytin]

I am......or I should say......I will.

When I drive my Marauder, most of the driving is on the highway, so I really didn't want to go to the 4.10s.
I'm actually pretty happy with the OEM 3.55s but I do want more acceleration.:D
I knew that the 3.73s are not worth the effort because of the small change from the OEM 3.55s.
I bought a set of Motive 3.90s gears and will be installing them when I remove my rear axle for a total build*.
I've had the 3.90 gearset Cryo-Rem treated so they require no break-in and will be bullet proof.
www.evansperformance.com (http://www.evansperformance.com)

*( Motive 3.90s, Detroit Truetrac, 31 spline axles, welded axle tubes, ARP stud kit/billet caps & SVO aluminum cover w/preload screws)

I think that the 3.90s will be a great for the Marauder.

Please keep us posted. I've wanted to put the Motive 3.90 set in my car for the last year but don't have the $$'s. I also like your choice of the Detroit TrueTrac - the clutches don't last long in my rear!

[Raudermaster]

I self-installed 3.73 gears. I think 3.90s would be perfect in this car. 4.10 is too much gear for a big luxo barge in my opinion. Cryo treated gears? Unless you are putting tons and tons of HP through them, that was a waste of $$. Gears are not going to wear out just highway cruising/daily driving.

Just look at his sig and you'll see why he went cryo.

[Stranger in the Black Sedan]

It's an NA 5.0 liter from what I see? I still don't see anything that regular performance gears wouldn't hold up to, especially for street driving

[Raudermaster]

You missed the bold part.

[Stranger in the Black Sedan]

The FIT pro charger that will be installed some day part? I don't see what I missed. Anyhow, not my expense, doesn't matter.

[Joe Walsh]

It's an NA 5.0 liter from what I see? I still don't see anything that regular performance gears wouldn't hold up to, especially for street driving

I do a fair amount of drag racing so I expect the gears to take some abuse.

Was the Cryo-Rem treatment essential for gear life?....No, but I've always believed in; "Do it right the first time, even if it costs a little more money."
If I am pulling the entire rear for a complete performance rebuild...why not?

I also had all four of Todd's Big Brake kit rotors cryo-treated to extend their service life.

[magindat]

By the time my new big arse tires come in, my effective ratio will be 3.90... I've done the computations and I think I'll like it.

4.10's rev a bit high on the highway and make it too easy to break loose with the SC. An effective 3.90 will squelch both those issues a little bit.

Keep in mind, as GreekGod posted above, tire diameter figures in to the equation just as much as the actual gear!

[Joe Walsh]

By the time my new big arse tires come in, my effective ratio will be 3.90... I've done the computations and I think I'll like it.

4.10's rev a bit high on the highway and make it too easy to break loose with the SC. An effective 3.90 will squelch both those issues a little bit.

Keep in mind, as GreekGod posted above, tire diameter figures in to the equation just as much as the actual gear!

YEP!

I run Nitto P305/45-18 555Rs on widened rims at the track and will run Nitto P295/45-18 555s on widened rims for the street.

Both should keep me real close to the 3.90 ratio.