Gears for boosted 6spd

[JustSomeGuy]

Building my car up to prepare for a Whipple install, ‘21 base 6spd. I’ll be installing a better limited slip diff, possibly the Torsen from the PP…? Wondering what the consensus is from 6G over what diff is best?

Also would like to know what gear ratio I should use while I’ve got it all apart…?

The car is not a DD, it’s partial hoon/drift and partial track. The car is purely for fun.

Thanks for any advice, this is my first venture in four wheels, any knowledge I have is two-wheels…

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[HKusp]

I have no advice for the center section other than to say, Eaton makes nice stuff. In the gearing for the Whipple powered cars, I like a nice 3.55 rear gear. That being said, I don't drift and I don't know where you are going to want your rev's/powerband to be. The Whipple doesn't really start pulling, by the "seat-o-the-pants-meter" until above 3500rpm and it gets really fun above 5500rpm. So you MAY want something a little higher like a 3.73 or 4.09 to get you there sooner as you aren't really looking for street car mileage and/or top speed.

 

[NJMike]

I have no advice for the center section other than to say, Eaton makes nice stuff. In the gearing for the Whipple powered cars, I like a nice 3.55 rear gear. That being said, I don't drift and I don't know where you are going to want your rev's/powerband to be. The Whipple doesn't really start pulling, by the "seat-o-the-pants-meter" until above 3500rpm and it gets really fun above 5500rpm. So you MAY want something a little higher like a 3.73 or 4.09 to get you there sooner as you aren't really looking for street car mileage and/or top speed.

what HKusp says - with 3.73s (tho I have Tremec, I believe the trans ratios are close enough to compare) I would prefer somewhere around the 3.30 rear gear, but this all depends on the goal. Drifting and track - you may want to keep it at 3.73 or higher. Depends on the goal and what you can live with since you cant have it both ways.

Also tire height will change the final gear ratio as well. Not sure of your plans on wheel/tire

 

[JustSomeGuy]

what HKusp says - with 3.73s (tho I have Tremec, I believe the trans ratios are close enough to compare) I would prefer somewhere around the 3.30 rear gear, but this all depends on the goal. Drifting and track - you may want to keep it at 3.73 or higher. Depends on the goal and what you can live with since you cant have it both ways.

Also tire height will change the final gear ratio as well. Not sure of your plans on wheel/tire

I am running 10x19 squared with 285/35 but fully expect that won’t be enough contact patch once I go FI. My only thoughts are that I’m heard wider rear tires can promote understeer which is the exact opposite of what I want… I’m sure with 700-800hp I’ll manage though

Any thoughts on a good rim/tire set up is appreciated, I’m definitely not just going for straight line so tiny rims with huge tires isn’t my thing…

 

[beefcake]

You can't go wrong with any of these they all hold up well

Wavetrac Ford 8.8" Differential (2015-2023 Mustang) 56.309.165WK
https://www.beefcakeracing.com/56-309-165wk/

Eaton Detroit Truetrac Differential Ford Mustang S550 Super 8.8in 34T - 917A731
https://www.beefcakeracing.com/eato...al-ford-mustang-s550-super-8-8in-34t-917a731/

Ford Racing Super 8.8" Torsen Differential (2015-2022 Mustang GT) M-4204-MT
https://www.beefcakeracing.com/m-4204-mt/

 

[NJMike]

I hear you on the rims/tires. Are you current rims 10"? You're going to want a 305 or 315 out back. You also may want to investigate upgrading the bushings, control arms and the like to stabilize the ride and mitigate any wheel hop. Good sticky tires and limiting deflection will keep the rear planted

 

[JustSomeGuy]

I hear you on the rims/tires. Are you current rims 10"? You're going to want a 305 or 315 out back. You also may want to investigate upgrading the bushings, control arms and the like to stabilize the ride and mitigate any wheel hop. Good sticky tires and limiting deflection will keep the rear planted

Yes I’m 19x10 right now. I have a good 70% of the Steeda chassis catalog on the car already. I’m trying to get it completely set and then throw the blower on once I’ve finished everything else

 

[stannypack]

I hear you on the rims/tires. Are you current rims 10"? You're going to want a 305 or 315 out back. You also may want to investigate upgrading the bushings, control arms and the like to stabilize the ride and mitigate any wheel hop. Good sticky tires and limiting deflection will keep the rear planted

are there any downsides to a fat tire like that on a 9.5" wheel? (aside from handling in turns which isn't my concern)

 

[JustSomeGuy]

are there any downsides to a fat tire like that on a 9.5" wheel? (aside from handling in turns which isn't my concern)

Handling in turns, which is my concern. I use my car for more than straight lines so I want a tire than will work well at multiple things, and I’m willing to give up some straight line performance for it.

 

[JustSomeGuy]

You can't go wrong with any of these they all hold up well

Wavetrac Ford 8.8" Differential (2015-2023 Mustang) 56.309.165WK
https://www.beefcakeracing.com/56-309-165wk/

Eaton Detroit Truetrac Differential Ford Mustang S550 Super 8.8in 34T - 917A731
https://www.beefcakeracing.com/eato...al-ford-mustang-s550-super-8-8in-34t-917a731/

Ford Racing Super 8.8" Torsen Differential (2015-2022 Mustang GT) M-4204-MT
https://www.beefcakeracing.com/m-4204-mt/

Thank you, any recommendations for gears?

 

[beefcake]

pretty much just ford on those

 

[JustSomeGuy]

pretty much just ford on those

I’m sorry I mean diff gear ratio.

 

[beefcake]

that depends on where you are going through the traps now, tire size, and where you want to go through

 

[Cory S]

A 3.31 gear will be what you’d love with a manual and PD blower.

 

[NJMike]

are there any downsides to a fat tire like that on a 9.5" wheel? (aside from handling in turns which isn't my concern)

I dont believe there is. You should be able to put a 275 or 285 on a 17 inch wheel, with good sticky tire for straight line traction

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