12 Bolt Rear-End
Thread Starter
TECH Regular
Joined: Jan 2005
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From: Pleasanton, CA
12 Bolt Rear-End I will be replacing my stock rear with a 12 bolt really soon. So my questions are as follows:
1. Can i do the swap myself in the garage?
2. If i go to 3.90's will i need the computer changed for the new gearing?
3. If i do need the computer changed, what options do i have for getting it changed?
4. I am pretty good at working on my car, maybe a bit above average mechanical abilities, is this in my level to do on my own?
5. What kinda gears should i get? I am going to immediately after get a Turbo cam to get ready for a phamspeed turbo, thats why i am thinking of either 3.90's or 3.73's. I have heard that with a turbo, 4.10's wind out too fast?
6. And lastely just any information someone could give me would be greatly appreciated and helpful. Thank you very much.
1. Can i do the swap myself in the garage?
2. If i go to 3.90's will i need the computer changed for the new gearing?
3. If i do need the computer changed, what options do i have for getting it changed?
4. I am pretty good at working on my car, maybe a bit above average mechanical abilities, is this in my level to do on my own?
5. What kinda gears should i get? I am going to immediately after get a Turbo cam to get ready for a phamspeed turbo, thats why i am thinking of either 3.90's or 3.73's. I have heard that with a turbo, 4.10's wind out too fast?
6. And lastely just any information someone could give me would be greatly appreciated and helpful. Thank you very much.
1. Its doable, but alot easier on a lift.
2. I didnt notice a big difference with my 3.73's.
3. LS1Edit/HPtuner/FlashScan/HPP3/Diablo/etc...
4. If u have the tools i dont see why not.
5. I would go with 3.73's. I have 550rwhp now and im running through the gears really fast. 1st/2nd and some of 3rd are useless on street tires.
6. Get something to help u move the rear end under the car if u are going to do it in your garage. Most likely u will need to extend the sway bar mount so u can reuse your rear sway bar. Make sure the Yoke is compatible with what u have on your Drive Shaft or change the one on the DS and balance it. I would also check the backlash and measurements on the rings before running it so u wont have it whinning on u after 500miles. Finally check the pinion angle when u install the rearend in the car and make sure its not off.
Good luck.
2. I didnt notice a big difference with my 3.73's.
3. LS1Edit/HPtuner/FlashScan/HPP3/Diablo/etc...
4. If u have the tools i dont see why not.
5. I would go with 3.73's. I have 550rwhp now and im running through the gears really fast. 1st/2nd and some of 3rd are useless on street tires.
6. Get something to help u move the rear end under the car if u are going to do it in your garage. Most likely u will need to extend the sway bar mount so u can reuse your rear sway bar. Make sure the Yoke is compatible with what u have on your Drive Shaft or change the one on the DS and balance it. I would also check the backlash and measurements on the rings before running it so u wont have it whinning on u after 500miles. Finally check the pinion angle when u install the rearend in the car and make sure its not off.
Good luck.
Like LSs1Power said.. if you put 4.10s in there your first couple gears will be useless on the street, probably 3rd too. I agree that you may want 3.73s.
I have a friend with a D1SC Procharger and 4.10s and even with the little amount of boost a SC makes at lower RPMs its rediculous to drive on the street. Freeway stabs = tire spin.
The boost comes on hard with a turbo, full boost at low RPM, so itll be even less tame on the street under WOT.
I have a friend with a D1SC Procharger and 4.10s and even with the little amount of boost a SC makes at lower RPMs its rediculous to drive on the street. Freeway stabs = tire spin.
The boost comes on hard with a turbo, full boost at low RPM, so itll be even less tame on the street under WOT.
Thread Starter
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Joined: Jan 2005
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From: Pleasanton, CA
So should i just stick with stock gears then? Im not exactly sure how that works. I want more of my gears to be useful, but doesnt having closer gears make my car faster.
If i have lots of horsepower, will i want longer gears, and then ill be able to use more of them, or do i want shorter gears and ill get to my top speed faster, but have trouble getting traction?
I should also mention that my goal on the stock bottom end is 550rwhp. And the month after the rear-end, i am probably going to be looking at getting a turbo cam installed, i think something around 230/234 .600 .605 116LSA. I think that cam would work good, but im not sure if that is the specs for a turbo cam. So i should be able to hit 550rwhp, so need the gear selection for somewhere around there, shortly after, forged bottom end will be in-sight. Trying to get ready for thess before they come.
If i have lots of horsepower, will i want longer gears, and then ill be able to use more of them, or do i want shorter gears and ill get to my top speed faster, but have trouble getting traction?
I should also mention that my goal on the stock bottom end is 550rwhp. And the month after the rear-end, i am probably going to be looking at getting a turbo cam installed, i think something around 230/234 .600 .605 116LSA. I think that cam would work good, but im not sure if that is the specs for a turbo cam. So i should be able to hit 550rwhp, so need the gear selection for somewhere around there, shortly after, forged bottom end will be in-sight. Trying to get ready for thess before they come.
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Choosing gears depends on your powerband and power level. If u have a car making around 400rwhp at 6300rpm then 4.10's will be perfect so u can use all the power band of the 4th gear before the 1/4 mile finish line. If u have over 500rwhp then u will run out of gear if u have 4.10's with street tires. So a 3.73 is a must if u dont want to shift to 5th gear. For example, when i installed my cam i gained 44rwhp from it, but because i was running stock gears i only gained 2mph in the 1/4mile because i shifted to 4th gear just before the finish line and i couldnt use the 4th gear powerband. Now with 550rwhp and 3.73 gears i see the shift light just before i get to the finish line which means with a good clutch i might have to shift to 5th gear or run a bigger tire in the back. U see what i mean.... Gears make a difference if u choose them right. For 550-650rwhp i would keep running the 3.73 gears. More than that 3.42's will be perfect. Good luck.
Thread Starter
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Joined: Jan 2005
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From: Pleasanton, CA
Would 3.42's or 3.73's be good on the street also. I know im gonna have traction problems, but street racing, i want to try and use as many gears as possible and still be able to really pull hard.
1. just did my swap this weekend on jack stands
2. yes...you will need to change for the 3.90s
3. LS1Edit, HPTuners, have someone tune it (mail order), etc.....
4. thats for you to decide.....its not "hard" but not "easy"
5. again...up to you......talk to others who have the turbo kit you want
6. I did 4.56 because even though I'm probubly in the 475-500rwhp range, my power band starts at 4K and goes high.....
2. yes...you will need to change for the 3.90s
3. LS1Edit, HPTuners, have someone tune it (mail order), etc.....
4. thats for you to decide.....its not "hard" but not "easy"
5. again...up to you......talk to others who have the turbo kit you want
6. I did 4.56 because even though I'm probubly in the 475-500rwhp range, my power band starts at 4K and goes high.....
TECH Junkie
Joined: Dec 2001
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From: Lakeland, FL
I say get the 4.10s, IF you run out of room in the 1/4 get a bigger rear tire.
I have the 4.10s with my combo and on nittos I can get it to hook in 2nd even with the nitrous as long as the tires are heated up good.
I have the 4.10s with my combo and on nittos I can get it to hook in 2nd even with the nitrous as long as the tires are heated up good.
TECH Senior Member
Joined: Apr 2004
Posts: 6,157
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From: Texas
Originally Posted by pewterta
i didnt notice any difference ...barely .....from 342 to 410.... i dont know what the all the hub bub is about 410 gears...
Thread Starter
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Joined: Jan 2005
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From: Pleasanton, CA
Ok, so lets say im hitting 550rwhp and 550+rwtq on the street. I actually plan on going to 18 inch rear wheels and ill probably do a mini-tub. I wanna be able to fit atleast 335's in the back. So lets say with 335 drag radials on 18's, and 550rwhp and 550+rwtq, what kinda gears would i want for the freeway. I still wanna be able to hook-up in as many gears as possible, but i also wanna get there really fast. Most likely i wont be able to use 3rd, but 4th and 5th would be nice to be able to use. I also plan on using a boost controller, so i wont always be at high hp. Also, can i use 3rd gear if i just dont punch it, and ease into it.
TECH Senior Member
Joined: Apr 2004
Posts: 6,157
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From: Texas
With that setup alot will depend on your driving ability. Then factors such as power band, street conditions, etc.
Hooking up on the street with 550+ is no easy task.
I have a freind thats making 660 at the wheels with a procharger and can spin his DRs at 80 mph.
For street only I would say 3.42s
Hooking up on the street with 550+ is no easy task.
I have a freind thats making 660 at the wheels with a procharger and can spin his DRs at 80 mph.
For street only I would say 3.42s
Staging Lane
Joined: Dec 2001
Posts: 85
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From: oregon
from reading some posts, looking at people's install pics, reading up and looking under my car, I can't imagine it being too complicated, if the 12 bolt is setup with everything in it and ready to go..
however, my biggest concern is lifting hte car up high enough, and then somehow physically dropping the old 10 bolt out and physically lifting the new 12 bolt in without killing myself..
I can imagine having a lift and those handy big jacks to support the rear's would make it a relative breeze..
has anyone actually done a swap in their driveway without a lift? Did you just jack up the rear with jackstands as high as you can, and then chained and balanced the rear on a jack to remove and install it?
however, my biggest concern is lifting hte car up high enough, and then somehow physically dropping the old 10 bolt out and physically lifting the new 12 bolt in without killing myself..
I can imagine having a lift and those handy big jacks to support the rear's would make it a relative breeze..
has anyone actually done a swap in their driveway without a lift? Did you just jack up the rear with jackstands as high as you can, and then chained and balanced the rear on a jack to remove and install it?
Originally Posted by ynneK
has anyone actually done a swap in their driveway without a lift? Did you just jack up the rear with jackstands as high as you can, and then chained and balanced the rear on a jack to remove and install it?
On The Tree
Joined: Nov 2004
Posts: 135
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From: Chicago
I've got a 12 Strange 12 bolt on the way.. Which gear should I pick for my 2000 TA, WS6 with around 380rwhp?? I am not a hard driver and mostly cruise so do you think a 3.42 would be good?? But I do like to go hard sometimes.. Thanks!