Question about gears
Question about gears Okay guys so i want to do a gear change.
The factory gears are 2.73 so that means i have a series 2 carrier correct?
And where is the best place to buy the gears from and what brand should i go with.
Also do they come with an install kit or is that something i will have to buy separate?
And last question. is there anything els i should replace when i do this swap?
I know i should have posted this in the gears&axles forum but i wanted to hear from the LT1 crowd.
thanks
The factory gears are 2.73 so that means i have a series 2 carrier correct?
And where is the best place to buy the gears from and what brand should i go with.
Also do they come with an install kit or is that something i will have to buy separate?
And last question. is there anything els i should replace when i do this swap?
I know i should have posted this in the gears&axles forum but i wanted to hear from the LT1 crowd.
thanks
You can get 3.73s designed for a 2-series carrier.
Go with the GM Motives if you want quiet. They are available on pretty much every site (Summit, Jegs, site vendors, etc.). In your search, you will likely find 7.5" and 7.626" ring and pinions - they are both the same.
You can buy an install kit (Ratech makes one), but it may be cheaper to just have the shop get the right parts for you.
Go with the GM Motives if you want quiet. They are available on pretty much every site (Summit, Jegs, site vendors, etc.). In your search, you will likely find 7.5" and 7.626" ring and pinions - they are both the same.
You can buy an install kit (Ratech makes one), but it may be cheaper to just have the shop get the right parts for you.
If i was you and your going to beat on the car a lot with any kind of sticky tire stick to a stock gear ratio. 3.42 would be my choice, and brand isnt too important as long as the are setu up right. When you go numerically higher in gears the ring and pinion will tend to break. You shouldent need new bearings if youve maintained your current rear, just a few special tools to install them and check the backlash and pinion depth.
hope that helped.
hope that helped.
TECH Regular
Joined: Oct 2008
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From: Rochester, NY
If youre sure you've got 2.73's, then you've definitely got a series 2 carrier. You'll need to buy a complete rebuild kit to do the job.
I usually buy my rear end related stuff from www.thunderracing.com, they've usually got good prices and fast shipping.
A complete rebuild kit comes with a pinion seal, pinion nut, pinion shims, pinion bearings/races, crush sleeve, carrier shims, carrier bearings/races, and a cover gasket. You'll need all this stuff, especially the bearings and races. Theyre cheap insurance, especially if your cars got a lot of miles on it. Don't wanna have to go tearing back into the differential 5,000 miles later because a bearing took a ****.
All the rebuild kits from 93-99 should be the same. Some of the 2000+ cars came with Zexel-Torsen carriers which have slightly different requirements than our Auburn carriers have. Somebody correct me if I'm wrong on that one.
Oh and don't forget youre gonna need 2 quarts of gear oil (usually 75w-90), and a 4oz bottle of GM Synchromesh additive.
I usually buy my rear end related stuff from www.thunderracing.com, they've usually got good prices and fast shipping.
A complete rebuild kit comes with a pinion seal, pinion nut, pinion shims, pinion bearings/races, crush sleeve, carrier shims, carrier bearings/races, and a cover gasket. You'll need all this stuff, especially the bearings and races. Theyre cheap insurance, especially if your cars got a lot of miles on it. Don't wanna have to go tearing back into the differential 5,000 miles later because a bearing took a ****.
All the rebuild kits from 93-99 should be the same. Some of the 2000+ cars came with Zexel-Torsen carriers which have slightly different requirements than our Auburn carriers have. Somebody correct me if I'm wrong on that one.
Oh and don't forget youre gonna need 2 quarts of gear oil (usually 75w-90), and a 4oz bottle of GM Synchromesh additive.
Last edited by tbag_skywalker; Aug 27, 2010 at 12:09 AM.
TECH Regular
Joined: Oct 2008
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From: Rochester, NY
Oh and brand isn't very incredibly important, since our stock 10-bolt's suck (our ring gears are only 7.5").
I'd say as long as you stick to a popular name brand you'll be alright. Most people seem to like Motive around here. I know SLP makes some good gears too. Richmond is popular, a whiney but tough gear for the money. And Strange Engineering is one of the best gears you can get if you wanna pay the extra buck.
I'd say as long as you stick to a popular name brand you'll be alright. Most people seem to like Motive around here. I know SLP makes some good gears too. Richmond is popular, a whiney but tough gear for the money. And Strange Engineering is one of the best gears you can get if you wanna pay the extra buck.
Okay thanks for the information it is very helpful.
also i want to make sure that my car has 2.73s in it and that the previous owner didn't change them out.
so is there any way of checking without getting into the rear end?
i have a 3800 stall converter just in case it makes a difference.
also i want to make sure that my car has 2.73s in it and that the previous owner didn't change them out.
so is there any way of checking without getting into the rear end?
i have a 3800 stall converter just in case it makes a difference.
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jack the rear of the car up and rotate the tires. Count how many revolutions you have to spin the tires to make one turn on the driveshaft. So if you have 2.73's then the tires should spin 2 and 3 quarter times to one whole turn of the driveshaft and so on and so on. hope that makes sense.
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Verdad Gallardo TECH Regular
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From: Rochester, NY
jack the rear of the car up and rotate the tires. Count how many revolutions you have to spin the tires to make one turn on the driveshaft. So if you have 2.73's then the tires should spin 2 and 3 quarter times to one whole turn of the driveshaft and so on and so on. hope that makes sense.
To determine a gear ratio you must jack the rear of the car up and rotate the driveshaft until the tires make one complete rotation. However many times you had to rotate the driveshaft represents what your gear ratio is.
In 1C3_MAN's case, he'll have to rotate the driveshaft 2.73 times in order to get one full rotation out of the back wheels.
TECH Regular
Joined: Oct 2008
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From: Rochester, NY
Very true statement.
Motive makes their 'Performance' line of gears in 4.10 for a series2 carrier. Richmond and Strange also make 4.10's for a series2 also. Don't have an A4 but it seems like overkill for a daily driver anyways.
Motive makes their 'Performance' line of gears in 4.10 for a series2 carrier. Richmond and Strange also make 4.10's for a series2 also. Don't have an A4 but it seems like overkill for a daily driver anyways.
Okay guys thanks for the answers.
I have one more question for you guys tho.
Let me start off by saying that i am new to gears and such so this might be a stupid question.
but how does going from 2.73s to 3.73s increase torque and acceleration because right now my drive shaft has to spin 2.7 times to get the rear tires to spin one time.
And with 3.73s my drive shaft would have to spin another full rotation to get the same result.
So in my head i cant figure out how that would be a gain in anything if my car would have to work harder for the same result.
So if anyone cares to explain this to me i would greatly appreciate it.
thanks again
I have one more question for you guys tho.
Let me start off by saying that i am new to gears and such so this might be a stupid question.
but how does going from 2.73s to 3.73s increase torque and acceleration because right now my drive shaft has to spin 2.7 times to get the rear tires to spin one time.
And with 3.73s my drive shaft would have to spin another full rotation to get the same result.
So in my head i cant figure out how that would be a gain in anything if my car would have to work harder for the same result.
So if anyone cares to explain this to me i would greatly appreciate it.
thanks again
You can get 3.73s designed for a 2-series carrier.
Go with the GM Motives if you want quiet. They are available on pretty much every site (Summit, Jegs, site vendors, etc.). In your search, you will likely find 7.5" and 7.626" ring and pinions - they are both the same.
You can buy an install kit (Ratech makes one), but it may be cheaper to just have the shop get the right parts for you.
Go with the GM Motives if you want quiet. They are available on pretty much every site (Summit, Jegs, site vendors, etc.). In your search, you will likely find 7.5" and 7.626" ring and pinions - they are both the same.
You can buy an install kit (Ratech makes one), but it may be cheaper to just have the shop get the right parts for you.
Staging Lane
Joined: Mar 2010
Posts: 66
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From: nc
i went from a 2.73 rear gear in my 97 z28 to a 3.23 geared rear from a 2000 t/a and am very happy with the milage and performance increase
plus when u swap the rears you get bigger rear brakes and a zexel posi unit to boot good used rears can be gotton very cheap
plus when u swap the rears you get bigger rear brakes and a zexel posi unit to boot good used rears can be gotton very cheap
TECH Regular
Joined: Oct 2008
Posts: 492
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From: Rochester, NY
Okay guys thanks for the answers.
I have one more question for you guys tho.
Let me start off by saying that i am new to gears and such so this might be a stupid question.
but how does going from 2.73s to 3.73s increase torque and acceleration because right now my drive shaft has to spin 2.7 times to get the rear tires to spin one time.
And with 3.73s my drive shaft would have to spin another full rotation to get the same result.
So in my head i cant figure out how that would be a gain in anything if my car would have to work harder for the same result.
So if anyone cares to explain this to me i would greatly appreciate it.
thanks again
I have one more question for you guys tho.
Let me start off by saying that i am new to gears and such so this might be a stupid question.
but how does going from 2.73s to 3.73s increase torque and acceleration because right now my drive shaft has to spin 2.7 times to get the rear tires to spin one time.
And with 3.73s my drive shaft would have to spin another full rotation to get the same result.
So in my head i cant figure out how that would be a gain in anything if my car would have to work harder for the same result.
So if anyone cares to explain this to me i would greatly appreciate it.
thanks again
Having to rotate the driveshaft one more time to get a full rotation of the tires requires less work because the motor essentially now has more leverage than it did with the 2.73's.
So even though the motors gotta spin a bit faster to get the tires spinning, it actually doesn't have to work as hard to reach its power band, and the easier it is for a motor to reach its powerband the faster the car will accelerate.
Well hopefully that didnt read like French lol, I don't think I personally can put that into better words.
I recently did this change from 2.73 to 3.42.
The first time (!) I did it I used Richmond Gears because they have a 3.42 THICK gear ring gear thatll work with the 2 series carrier you have.
Of course, I found out later that while Richmond gears are the strongest due to their cut, theyre also most prone to noise, meaning hum on the highway. I was cursed with this.
After exhaustive research, I concluded that original GM gears are the quietest. While they are costly at a GM dealership, JAWS has them reasonablely priced. They are made by AAM, the OEM for GM. I purchased from JAWS and had no issues and the stuff arrived quickly.
This causes another problem. These (GM/AAM) gears are not available in a thick version so going from 2.73 to 3.42, youll need a three series carrier. I went with a Eaton Posi. Nice and quiet now and its a great posi.
You could choose to opt for the aftermarket (non GM) gears that are thicker but be aware nobody will guarantee their gears wont make noise.
A word about spacers to put non thick three series gears on a two series carrier: The ring gear is centered in a machined groove on the carrier. A spacer will also locate itself in this groove but theres nothing positively locating the ring gear on the spacer. Its not a good idea to use a spacer.
This is about the maximum investment anyone should make into these crappy 10 bolt 7.5 inch rear ends. If youre gonna make power, step up to a Strange 12 bolt.
The first time (!) I did it I used Richmond Gears because they have a 3.42 THICK gear ring gear thatll work with the 2 series carrier you have.
Of course, I found out later that while Richmond gears are the strongest due to their cut, theyre also most prone to noise, meaning hum on the highway. I was cursed with this.
After exhaustive research, I concluded that original GM gears are the quietest. While they are costly at a GM dealership, JAWS has them reasonablely priced. They are made by AAM, the OEM for GM. I purchased from JAWS and had no issues and the stuff arrived quickly.
This causes another problem. These (GM/AAM) gears are not available in a thick version so going from 2.73 to 3.42, youll need a three series carrier. I went with a Eaton Posi. Nice and quiet now and its a great posi.
You could choose to opt for the aftermarket (non GM) gears that are thicker but be aware nobody will guarantee their gears wont make noise.
A word about spacers to put non thick three series gears on a two series carrier: The ring gear is centered in a machined groove on the carrier. A spacer will also locate itself in this groove but theres nothing positively locating the ring gear on the spacer. Its not a good idea to use a spacer.
This is about the maximum investment anyone should make into these crappy 10 bolt 7.5 inch rear ends. If youre gonna make power, step up to a Strange 12 bolt.
Confirming what is above, Motive gears are not GM, they are made in Italy. Strange gears are made by Motive. Not that that’s a bad thing mind you. Just so you’re straight on who makes what.
If you’re gonna do this job, you should do all the bearings and seals, axles, pinion, everything. Inspect the axles real good at the bearing races. Moser has good axles that won’t break your bank that are better then the originals.
You’ll need a competent shop to do the work for you, it’s often best to let them get the parts as they won’t warranty anything you furnish. You’ll want a guarantee on this kind of work.
DO NOT use a synthetic gear lube. Believe it or not, it’s too slippery for a posi rear. Posi differentials need a bit of friction to allow the rear to attain the proper preload settings. A good quality mineral-based oil with the proper limited slip additive and you’ll be good to go. Bob is the Oil Guy is our friend......
If you’re gonna do this job, you should do all the bearings and seals, axles, pinion, everything. Inspect the axles real good at the bearing races. Moser has good axles that won’t break your bank that are better then the originals.
You’ll need a competent shop to do the work for you, it’s often best to let them get the parts as they won’t warranty anything you furnish. You’ll want a guarantee on this kind of work.
DO NOT use a synthetic gear lube. Believe it or not, it’s too slippery for a posi rear. Posi differentials need a bit of friction to allow the rear to attain the proper preload settings. A good quality mineral-based oil with the proper limited slip additive and you’ll be good to go. Bob is the Oil Guy is our friend......
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Joined: Oct 2008
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From: Rochester, NY
Maybe Motive owns US Gear? Not that I have anyhting against Motive, they're good gears.