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Discussion Starter #1 (Edited)
Having a hard time deciding which gears to go with 373's or 390's.

Doing gears for the short term just to change things up a bit and will be swapping again when my turbos go on.

416 stroker making 523/507

Don't do any drag racing,street car only.

I've never swapped gears before,but have read they really make a difference so wanting to give it a go.

Is there really a much noticeable difference over stock gears switching to 373's?
 

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I dunno but if my calcs are right the .73s give and 8% increase and the .91s give an 13% increase over stock which I think is 3.46.

Something that's on my list too and based on feedback I've seen I'd go the .73 route. For the M6 cars the .93s make 1st gear useless. For you it should feel like adding a 40 hp or so bolt on. Of course rpm will be higher as will the rpm you cruise at on the highway and mpgs will drop some but doesn't like a factor to you.
When you go forced you'll want to go with taller gears so maybe go all out with the .93s while you're n/a knowing its temporary?
 

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I have been thinking about doing 3.91s for a while. Only drawback is I don't want the whining sound. If someone can point me to some Aussie gears I'd be most grateful. Sorry to threadjack.Have you decided where you would get the gears from? By the way, 403ci M6.
 

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3.91s
 

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Discussion Starter #5
I dunno but if my calcs are right the .73s give and 8% increase and the .91s give an 13% increase over stock which I think is 3.46.

Something that's on my list too and based on feedback I've seen I'd go the .73 route. For the M6 cars the .93s make 1st gear useless. For you it should feel like adding a 40 hp or so bolt on. Of course rpm will be higher as will the rpm you cruise at on the highway and mpgs will drop some but doesn't like a factor to you.
When you go forced you'll want to go with taller gears so maybe go all out with the .93s while you're n/a knowing its temporary?

Yeah I know I'll have to swap again for the turbos. I think I'm gonna go with the 3.90's for the extra get off.
 

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Discussion Starter #6 (Edited)
I have been thinking about doing 3.91s for a while. Only drawback is I don't want the whining sound. If someone can point me to some Aussie gears I'd be most grateful. Sorry to threadjack.Have you decided where you would get the gears from? By the way, 403ci M6.
I'm buying a used set from my engine builder,my exhaust will overpower the whine if I have any.
 

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I have been thinking about doing 3.91s for a while. Only drawback is I don't want the whining sound. If someone can point me to some Aussie gears I'd be most grateful. Sorry to threadjack.Have you decided where you would get the gears from? By the way, 403ci M6.
I believe Complete Street Performance has the Aussie gears.
 

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Discussion Starter #8
I've decided on the 3.90's and have install setup for first of August.
Think I'll have traction issues with 523/507 to the ground?

I have Billet Specialtie 15x10's on the way with 275/50 MT R's.
 

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I'm buying a used set from my engine builder,my exhaust will overpower the whine if I have any.
If it whines, you’ll hear it.
 

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Discussion Starter #11
At what speed do 3.90's top out at around 6500 rpms? Dropping my car off tomorrow for gear install.

Have the option for the 3.73's as well,but leaning towards 3.90's.

Street car only with no time at the drag strip,occassional roll races though.
 

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TACHNUP
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For some reason I completely skipped over the two times he said "no drag racing" because I just assumed he was talking about what speed to cross the 1/4 at in 4th gear, whoops.
 

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Discussion Starter #16
Dropped my car off to get the 3.90's installed, hope I made the right choice.
 

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Dropped my car off to get the 3.90's installed, hope I made the right choice.
Absolutely the right choice, you’re gonna love them. You can roll in 5th at 25mph, didn’t even use 4th gear driving around town or even getting on the freeway. Never really beat on the car much or at all but for a daily and bolt ons only I’d go through tires like a mofo.
 

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Got the auto and went with 3.91's a few years ago. It's like night and day compared to the stock gears.
 

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Discussion Starter #20
Picked up my car today after install and now have ABS fault and no traction control.

Think I've read issues with axle/stub play with a TruTrac can cause this,but don't know.

Can't figure it out so may just swap TruTrac back out for stock.

Anyone ever had this issue? I never had it before the gear swap.
 
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