How do I tell the difference in a 2 series gear set from a 3 series gear set? And will a 2 series work in a 3 series rearend if that is the case and they are 2 series? Any help is appreciated. Thanks, Jarred

 

2 series gears are 3.08 and down. 3 series are 3.23 and up. The 3 series gear is a little thinner and can fit a 2 series carrier with a spacer, but not the other way around. To tell if you have a 2 or 3 series carrier stick the posi on end and measure up to the ring gear mounting flange from the ground and you get the following measurement (using a tape measure)

2 series = 5 1/4"
3 series = 4 7/8"

You can see the 3 series gear would have to be thinner in order to reach the pinion. 2 series gears CANNOT work in a 3 series carrier, but a 3 series gear can work in a 2 series carrier with a spacer.

 

I already answered my own ? but thank you. Turns out they are 3 series gears too so I'm good

 

If you were putting 3-series gears (ie: 3.42's) onto a 2-series carrier (ie: 2.73) I really wouldn't recommend using the spacer. By doing so, you're doubling the number shear points on the bolts holding the ring gear on, and we all know how strong 10-bolts are to begin with. I would always recommend buying the correct gear ratio for the matching carrier (what I mean is, you can buy 3.42's, 3.73's, 4.10's that are INTENDED to go on 2-series carriers ... they're just built thicker).

 

Well I have a 3 series carrier and 3 series gears so I'm good. Now I just hope I don't need a whole new center section as well

 

I'm replacing my differential and have run into a problem.

While removing the original Auburn Cone, I noted that there were two thick shims on the ring gear side and nothing on the right hand side of the differential. When I began reassembling with the new Torsen (same ring and pinion) I have found there is too much backlash, about .025 inch. I can't move the ring gear and differential any further over because the right hand side bearing race for the differential is already against the axle housing. There is no shim to remove to let the diff with ring gear move to the right.

Even if I'm able to figure a way to move the ring and differential another .020 over to get the correct backlash, I have the driver side bearing partially out of the axle housing bearing seat, by what looks like more than a quarter inch. This is how it must have been with the Auburn Cone. There is a quarter inch or more of shims on the one side and nothing on the other.

It almost looks like I have 3 series gears and a 2 series differential but I'm fairly positive I'm working with factory 2 series matched outfits. The Auburn really appears to be the original rear end and the purchased 2 series Torsen is supposed to be a factory matched outfit with it's original 2 series gearing. Both were 2.73 (factory GU2).

I know you don't recommend the spacer but it almost looks like this is what I need unless I replace the gear set. Something I don't want to do at this point in time. Other than what you have mentioned, do you have any other thoughts or advice on what I should consider? Surely this situation couldn't be do to extreme tolerances....

Thanks.

 

Spacers are not as bad as some people make them sound (not attacking you capn). If it is bolted down correctly there should be no problem. If you are worried about the number of threads going into the ring gear, get longer bolts.

 

You're right, he's a good sort with a lot of help.

I found my problem and solution. The problem is assumption; because the RPO shows a GU2 and the car really appeared unmodified and I thought I counted properly while rotating the rear wheel one full turn that I had 2.73 gears in my 95 A4. So I bought a lightly used 2 series carrier off ebay when I felt my posi was on it's way out.

Here's the solution. I called Bob at Riverside Gear in MI.. By his gruff but helpful instructions, I pulled my diff out and started counting teeth. He also told me how to measure the carriers to determine 2 from 3. I had measured the carriers from the wrong end before. This time I set them on a table with the ring gear flange closest to the table surface and measured down to the table with the stem of my verniers. My Torsen (also known to him as a Gleason differential) was 1.625 inches. The Auburn was 1.920. That made the Torsen a 2 series and Auburn a 3.

After counting teeth I discovered my Auburn gears were 13 and 42 which makes them a 3.23 ratio and not 2.73 (15/41 with the Torsen) that I had assumed. The 3.23 of course is what I would rather have. BTW, it looks to me that a 2.73 gearset is inherently stronger.

Anyhow Bob at Riverside Gears explained the spacer I needed would be a weak point but as he remarked, it probably won't be the weakest link in that tiny 7.5 10 bolt rear end. Something else will break before those 10 bolts. Anyway $50 for the kit, which includes his advice, longer bolts, loctite and shipping and I'm feeling much happier now. I hope this helps someone else as well.

Regards

 

Glad you got it sorted out. That makes a little more sense.

I agree that using a spacer in the stock 10-bolt probably isn't the "worst" thing either. You're right ... they're not that strong to begin with anyway. But I know that a friend of ours sheared the bolts TWICE in his big-block Chevelle trying to use a spacer, so he eventually had to get a gear set that would bolt on direct without a spacer. I've heard from others that it's not a wise thing to do for racing or hard street driving. For a day-to-day car though, it probably wouldn't hurt at all, but it's just not the best thing for a car that's going to be abused!

 

Well, there's not a happy ending to this yet.

The spacer came and the first thing off, it didn't sit flat upon the gear flange. Theres a good radius on the carrier and very little of one on the spacer. I can fix that I said. I don't have access right now to a lathe but my du-more grinder can whittle the edge away. But that's not the real problem. The spacer is 5/16 thick. The register (or pilot) on the carrier is 3/8. This would be enough to register the ring gear and the spacer if the ring gear didn't have a 1/8 chamfer. In other words, the ring gear is only located by the bolts through the spacer. This won't work.... I could face the spacer down to about .200 but then we're messing with the shims to locate the whole shebang.

I'm either going to bite the bullet and buy a 3 series carrier or get those thick Richmond gears. I really don't want to pull the pinion and deal with that so I'm thinking I will wait and shop around until I can come up with another carrier.

I learned my lesson with the spacer. It's just too mickey mouse in my situation. But hey, I picked up my new SS hood today. Very nice looking piece of work. Check out WWW.BOA-FX.COM. I bought a Harwood for my 95 and it's nothing compared to this one. I had to think of something to cheer me up. Feeling better now....

 

I called Shep at www.drivetrain.com - what a helpful person! He explained that it's normal for the ring gear to be located by just the bolts on a spacer with the 7.5 10 bolt axle. He told me how to check it after installation and explained that a little run-out is acceptable and told me how much to accept. He even gave me tips on how to insure a good installation, to save the oil and check the bolts after 250 to 500 miles. As I gathered from you, as long as I don't expect too much, don't do hard launches with slicks, the spacer will be adequate for a little rough housing and even some time slips at the drags. The one thing in my favor is the A4. Anyway, I installed the thing today. Ended up with .007 to .010 thou of backlash with a total of .003 run-out. I was surprised at how it all came together. Thanks for your input.

Regards