Superformance Ring and Pinion

[frankym]

Been searching the forum unsuccessfully to find out the best way get my car to be useful in first gear. I have a keith craft stroker 427, 579hp 583 tq and a tko 600 5 speed. Im at ~3k rpm at 60 in 5th. Im thinking I might have a 411 in the 8.8 Ford rear diff. Curious if i went to a 3.31 ring and pinion set. Im almost better off launching the car in second gear. I can hit the rev limiter in first gear after going 10 feet. Curious if folks have had good results for a little more driveability with a shorter final gear set.

[Pman1961]

I have a 3:31 gear set from a 8.8 Superformance differential we just swapped for lower gears recently. I was going to list for sale as early as this weekend. If interested PM me.

[frankym]

Thanks but for all the labor effort wnd the relative cheap cost of the parts, it makes sense to go with new parts. Was hoping someone could tell me the exact package to buy. I may need to cout the spline grooves to get the right setup.

[Pman1961]

We changed the rear gears on his car to 4:30's. Replaced the TKO 600 for a T56 six speed with 2:66 first gear and went to 325 rear tires. His first gear feels equivalent to my first gear using a TKO 600 with 2:97 first gear and 3:46 rears. I love the swap and plan on doing mine. A lot of work and expense but the T56 shifts soooo much better than the TKO's and the lower gear gives you more get up and go. And before people blow a gasket and say 4:30's he can cruise at 75 miles per hour 2500 rpm in sixth gear!

[Pman1961]

Do you know which TKO 600 is in your car? The 4617 has 2:87 first gear and the 5008 has a 3:27 first gear.

[jhv48]

I have a newer SPF with the 3:46 rear end. I would like to swap out the rear end for a 3:15-3:27 ratio. Not sure what’s best. Buy a new rear end or just the gears.
Anyone done this?

[RockBit]

Frankym - From the data, it appears that you have a 4.56 gear in your Ford 8.8. That is really low, as you know. You would be better off with either a 3.31 or 3.55 gear.

With the 3.31, RPM versus speed in 5th gear would be:
60 @ 2100
70 @ 2450
80 @ 2800

With the 3.55 in 5th gear you would get approximately:
60 @ 2250
70 @ 2620
80 @ 3000

Either of these gear choices would make first gear more useable.

[eschaider]

Originally Posted by frankym

Been searching the forum unsuccessfully to find out the best way get my car to be useful in first gear. ... Im almost better off launching the car in second gear. I can hit the rev limiter in first gear after going 10 feet. Curious if folks have had good results for a little more driveability with a shorter final gear set.

A shorter final drive will cause you to run the engine higher in the rpm than you do now at any given vehicle speed. If you want to slow down the engine then you want a taller gear which would be a smaller number numerically. If you want more engine speed at all vehicle speeds then you need a shorter final gear, which would be a bigger number numerically.

Depending on your SPF chassis number there are several different rear ends that you might have. If you are familiar with what the different housings look like, you should take a look underneath to determine which you have before ordering gears. Some gearsets can be impressively pricey. If you are not familiar enough to do a visual identification then call Hillbank and ask them what rear end your vehicle number has.

Originally Posted by jhv48

I have a newer SPF with the 3:46 rear end. I would like to swap out the rear end for a 3:15-3:27 ratio. Not sure what’s best. Buy a new rear end or just the gears.
Anyone done this?

You either have an Australian BTR unit or one of the Getrag center sections. I don't remember when the change over from the BTR's occurred. The BTR ring and pinion will impress you with how expensive it is. I am not sure about the Getrag.

I had the BTR center and converted mine back to the Ford 8.8 for easier access to parts, stronger parts and lower costs for parts. If you do that you will need a chassis shop to fabricate the mounts unless you possess those skills. You will also need replacement axles. I recommend the G-Force half shafts with their HD 930 Porsche CV joints, click here => GForce Cobra Axles. Those particular axles are made for an 03/04 Cobra with a 31 spline 8.8 center. The axle shafts will need to be slightly different length for a replica but GForce can easily accommodate that.

All in all you will be in the tank for about $3,500 including the chassis work, but you will have a bullet proof rear end — done correctly. Be sure to get the billet steel carrier caps from MW and use an aluminum 8.8 center out of a 2007-2010 Explorer they are more robust.

The housing on the left, in the epic below, is the one you want. It is from a 2007-2010 Explorer. The one on the right is the passenger car version. The Explorer version is more robust.




Ed

p.s. Go over to the Second Strike Gearing calculator to help you make informed gearing choices. Click here => Gearing Calc