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18 Posts
(also now available in the Tech/FAQ section)

1. I have a leak, where is it coming from?

The two most common places for a rear end to leak are the pinion seal (the front of the housing) and the rear end cover. Pinion seal seepage is very normal for an f-body, as long as you check your fluid and it doesn?t leave drips on the ground, it is usually okay. Many times people take their cars to be fixed at the dealership only to have it leak again. The rear cover will leak because of a bad gasket/poor use of RTV sealant. You will notice a few drips hanging from the very bottom of the housing, and the area around it may be damp as well. Fixing a rear cover leak is very simple ? remove the cover, scrape the old gasket/RTV off of the cover & the housing, lay down fresh RTV sealant on the cover, bolt it back on and add the appropriate fluid (75w90 & GM rear end additive). The rear end is full when fluid begins to spill out of the drain plug on side of the housing.

One should not attempt to fix a pinion seal leak unless they are familiar with the way a rear end goes together, because pinion depth & crush sleeves are vital to correct setup. Fixing a pinion seal includes removing the driveshaft, pinion nut, washer, yoke, and old seal. The housing should be clean from nicks, and the yoke should be cleaned with a scotchbrite pad to get rid of any unsmooth areas before the new seal is installed. When retightening the pinion nut, it is important not to overcrush the crush sleeve. Pinion bearing preload needs 24-32 inch/lbs tq with a new crush sleeve, or 8-12 inch/lbs if reusing your old sleeve.

Another area that leaks, although somewhat uncommon, is an axle seal. If there is fluid dripping/seeping out of the axle seal, it must be replaced. In order to look at the seal, you will need to remove the brake caliper & rotor. The seal is the piece surrounding the axle itself.

2. What gears are best for my car?

To find what gears are best for you, it would be wise to use the search function of this website to look at cars that are similar to yours in modification. In general, most people with 6 speed cars choose 4.10s, and most people with automatic cars choose 3.73s. However once you start adding modifications like a new camshaft or a forced induction system, you should spend time researching before you decide. Automatic LS1 cars come with 3.23s or 2.73s from the factory, and six speed LS1 cars have 3.42 gears.

3. What is a gear ratio, and how do I know what I have?

A gear ratio is the number of teeth on one gear compared to another. To find the ratio, you divide the number of teeth on the driven gear by the number of teeth on the driving gear. For instance, the number of teeth on a ring (driven) gear is 41. The number of teeth on a pinion (driving) gear is 10. 41 divided by 10 = 4.10.

4. What can I expect to pay for a gear upgrade?

A set of gears themselves will cost $150-$250 depending on what brand you purchase. Most shops will charge $250-$400 in labor, and may add more for supplies. Overall, you will spend $400-$700 on a gear change depending on your location. Don?t skip out and go with the cheapest one ? be certain that a trained professional is handling your installation!

5. Can I set up my own rear end?

You may or may not be able to, depending on your level experience. If you perform all of your own installations and are patient, it is possible to perform it yourself, but it would really help to have someone who has done it before to help you through your first time. Setting up pinion depth & backlash are vital to a well-working rear end. Gears that are not set up correctly will whine or howl, and fail prematurely.

If you want to read more about installing gears, visit the site below for a complete how-to.

6. Is a 10 bolt even worth putting money into?

Theoretically, a 10 bolt is going to be weaker than a 12 bolt, or Ford 9 inch rear end due to the size, but that doesn?t make it useless. Some people have more luck with 10 bolts than others, obviously. The life of your rear end will depend on how you drive and maintain your car. If you are running slicks at the drag strip and launching from 6,000 rpms, something is bound to break eventually. If you don?t keep up on fluid and let it run low, the bearings will fail prematurely. If your gears are not set up correctly, it?s more bad news. However there ARE people out there who have ridden their 10 bolt right into 10 second passes in the quarter mile. Two of our personal cars, a bolt-on 2000 Z28 M6 with Motive 4.10s and a supercharged 1993 Firebird Formula with Richmond 3.73s are taken to the dragstrip weekly with drag radials, launched from at least 4,000 rpms, and have no issues to speak of thus far?

Whether you will need a ?better? rear end is up to you. If you are replacing parts of your 10 bolt every other week, yes, it?s time for an upgrade. However if it is your daily driver/occasional track car, there?s no sense in upgrading until something breaks. A new 12 bolt runs at least $2,000+, and that is more money that can be put into a nice heads & cam package, or wheels, or whatever your fancy. People do encounter problems with 12 bolts and 9 inches as well; they are not the ultimate solution!

7. Are some gears noisier than others?

Yes, some gears (such as Richmond) will be noisier than others. However, the noise should not be overpowering. If it is unbearable, the gears may have been set up incorrectly.

8. What is backlash?

Backlash is the play between the ring and the pinion, i.e., how much space there is exactly before the pinion actually contacts the ring. It is measured with a dial indicator gauge (either magnetic or clip on). Too little backlash will make for a bad whine, and too much makes for a sloppy setup. In general, different manufacturers call for .006? - .010? backlash (some may even allow for more).

9. What is a ?paddle?, and a paddle kit for that matter?

A paddle takes the place of an axle pin in a Torsen differential car. Instead of a thin cylinder, it is shaped like a block and is held in with an 8mm bolt. The purpose of a paddle or axle pin is keep the axles pushed outward, and thus retained with the c-clips. Sometimes when installing different gears, a paddle kit may be needed for re-installation. Depending on the brand & gear ratio of the selected gears, the ring gear may be too wide after installation to insert the paddle. SLP?s paddle kit is a two piece paddle that allows it to fit. To decide if you will need one or not, be sure to contact the sponsor from whom you are purchasing the gears.

10. Besides gears, what do I need for an install?

It is good practice to replace all of the bearings when installing new gears?if you have the rear apart anyway; it only takes extra minutes to replace the bearings. A good master installation kit will include everything you need, but specifically if you choose to replace everything you will need: carrier bearings (2), front pinion bearing, rear pinion bearing, crush sleeve, pinion nut, axle bearings (2), axle seals (2), pinion seal, a set of shims, gear paint, loctite, RTV gasket maker, 75w90 (2), GM rear end additive (for LSDs). It is also a good idea to replace the ring gear bolts, which may stretch over time. They are left hand thread, fyi.

11. I can?t get my axles out, they won?t slide in far enough to remove the c-clips!

Got a car with traction control? The sensor is prohibiting the axle to move in far enough. Remove the sensor from the backing plate and it will allow you more room to slide it inward to drop the c-clips.

12. What is a series 2 or series 3 carrier, and what do I have?

A 2 series carrier is a car that came with 3.08s or lower from the factory (i.e. all of your 2.73 cars). A 3 series carrier is a car that came with 3.23s or higher. This is very important when you order new gears, as they will differ from 2 to 3 series carrier!

Some helpful definitions of common rear-end terms:

? the play between the ring and pinion gear

? a c-shaped piece of metal used to retain an axle shaft

Carrier- the piece that is containing the limited slip clutches, spider gears, and the piece to which the ring gear bolts

Coast ? a load condition in which the vehicle is driving the engine, as during deceleration

Differential ? a gear arrangement that allows the drive wheels to be driven at different speeds

? a load condition where the engine is applying power to the drive wheels

? the outer end of a gear tooth

Limited slip differential (LSD) ? a differential that uses internal clutches to limit the speed difference between the axles.

Pinion depth ? how deep the pinion gear is in the housing, where it contacts the ring gear

Race ? a hardened surface for the bearing rollers/balls to roll on (kind of ?cups? the bearing)

Toe ? the inner end of a ring gear tooth

Ten bolt
? the rear end under an fbody, characterized by 10 bolts on the ring gear (or rear cover )

36 Posts
I Have a 2-series carrier...I heard about a spacer needed for the 2 series. Point blank, I want 3.73's and what is the best way of doing so. Thanks.

239 Posts
You have to order the right ring and pinion for your carrier, I think that 3.08 or 3.23 and lower you need the thicker ring gear, and the 3.42 and higher you need the thinner ring gear.

135 Posts
I was just under my car shaking exhaust parts to see if I can figure out where that annoying vibration/squeaking is coming from and noticed some wetness in front of the pinion seal. I wasn't all the way under the car to see the actual seal or drive shaft, but I could see grease on the exhaust pipe and the inside of the stabilizer bar that that runs along side the drive shaft. It's pretty wet even though I've not noticed any drips on the ground. Then again, I don't drive the car that much to begin with. Thanks for this article. I would have just tried to replace the pinion seal until seeing in here that it's common. Now I know to just check the fluid and top it off if needed. That way my gears won't go out on me. I've heard that's common on these cars, but now I know it's probably because they get low on grease and then fail.

861 Posts
I had a moser ford 9" installed in my car and now what i take turns back up or drive slow it clicks and kinda hops wich kinda sucks not a daily driver tho. The installer told me that its normral because of the posi unit or locker or something like that
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