Rear end/gearing question
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Rear end/gearing question I am going to be purchasing a 12 bolt for my 96 m6 trans am and was wondering if 4.30 gearing would be to short of a gear for daily driving. I plan on doing H/C also if it matters but for a little while probably only going to be the rear end. I was going to go 4.10 but i found a decent deal on a 12 bolt with 4.30s.
Also is there an advantage of going with a 12 bolt over a 9" if i only plan on making around 400-450 rwhp. I know 9" is generally stronger but for the HP im looking at 12 bolt will be better suited i would assume right?
thanks!
Also is there an advantage of going with a 12 bolt over a 9" if i only plan on making around 400-450 rwhp. I know 9" is generally stronger but for the HP im looking at 12 bolt will be better suited i would assume right?
thanks!
Really depends on your intensions for the car! 4.30 gear with a 28" drag tire would be SICK..... As for daily driving well you have 6 gears to use!
Screw the 9" its inefficient and weighs a ton....Go 12 bolt
Screw the 9" its inefficient and weighs a ton....Go 12 bolt
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Cars first responsibility is my daily driver so slicks wont really ever find its way to the rear. It does have Nitto 555r's though, and thats what i thought about the 9" for my application.
If your not using slicks, I would just see how the old 10 bolt handles it for now; it's sticky tires that usually kill them....I'm in the same boat, no slicks, just street tires with a 383/C/I/H with a 6spd and 4.10's 
....I do have a girdle though...so far so good. It's definitely overkill on a stock LT1. I think 10 bolts get a bad rep on here....I've beat the hell out of mine since 1997 and only recently had the stock posi unit die....my other car has a LS1 and a 6sp with full bolt ons and have done plenty of shenanigans/abuse with it for years without any problems either. It's fools that try 5000+ RPM clutch drops on slicks that have most problems.....of course it would be pretty cool to do 5000 RPM clutch drops on slicks with a proper rear end 
....I do have a girdle though...so far so good. It's definitely overkill on a stock LT1. I think 10 bolts get a bad rep on here....I've beat the hell out of mine since 1997 and only recently had the stock posi unit die....my other car has a LS1 and a 6sp with full bolt ons and have done plenty of shenanigans/abuse with it for years without any problems either. It's fools that try 5000+ RPM clutch drops on slicks that have most problems.....of course it would be pretty cool to do 5000 RPM clutch drops on slicks with a proper rear end I'm putting together a similar setup built motor h/c/single plane intake, built m6, S60 4.30 gears with a locker. for the street 315x35x17's and for track 295x45x17's. With double od 6th gear is only 2.15 which will actually make 6th more usable imo.
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From: wisconsin
So for a street car that will almost never see the track would you guys recommend doing H/C before the rear end. I'm eventually doing both, but there is going to be a decent wait between them. Kind of torn between the two.
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You'll get lots of opinions on that....it's up to you. 100+ extra HP is a lot more fun and usable everyday to me than launching on slicks for now.
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If you have a good deal on a local 12 bolt grab that while you can, good deals on used rears without shipping are hard to find. 4.30s would be a good gear with a H/C combo, I know 4.10s work good for me. If you do the engine first you'll end up wishing you bought the 12 bolt when you had the opportunity.
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It's such a hard decision lol. I know the smart idea is 12 bolt first. I know the fun idea is H/C. So i need to decide smart or fun. The 4.30 gears would make the car more fun to drive though also... 
Get the 12 bolt while you can.
As to the question if 4.30 gears are too much? .....hell no! With an M6, 4.10's would be the bare minimum for me. 4.30's or 4.56's much better. Your 6th gear makes highway cruising just fine with either.
As to the question if 4.30 gears are too much? .....hell no! With an M6, 4.10's would be the bare minimum for me. 4.30's or 4.56's much better. Your 6th gear makes highway cruising just fine with either.
The real question to ask yourself....Can you afford it if you break your 10 bolt after you do heads/cam? If this is your only mode of transport, yea...12 bolt first; if you have another DD and this car is a toy like mine, it's not the end of the world if it blows up...just means it's time to start 12 bolt shopping while it's out of commission.
I've had both, and I'd go with the 4.30:1 twelve bolt now.....then do h/c when you can. Especially since this is for a daily driver. Low gears are plenty liveable with the .50:1 sixth gear and lots of fun. Probably won't really effect your mpg's too much either. You will be glad you have the insurance of a stout rear when you do modify the engine and the steep gear will compliment the shift north in your rpm range that heads and cam will give.
Crazy I know...
Also I would not recommend a 12 bolt for a stick shift car personally.
I went with 4.30's in my S60 and will be running 28 x 10.50 x 15 slicks. Should roll out...
It really plays into the cam choice, and desired use, etc.
I really have too much gear for a dedicated nitrous car. N/A car you want to be at redline going through the traps. Nitrous car makes tq so you run a taller gear. Its hard to have the best of both of worlds so you really need to decide what youre going to set up the car for, and commit to it.
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Car is a daily driver period. I just want a fun daily driver. Prolly wont see track more than 2-3 times a year if any at all. Spool is out of the question because im not DD a car with a spool.
I personally don't care what i get a 12 bolt or a 9" what ever i get the best deal on would be my choice. Don't want to modify or purchase a new drive shaft either...
I personally don't care what i get a 12 bolt or a 9" what ever i get the best deal on would be my choice. Don't want to modify or purchase a new drive shaft either...
