I have 373 gears in my z28 wondering if they are 3 series or not. I know that 373 gears should be 3 series but is this one. The reason i ask is i want to put in a posi unit from a 89 camaro with 2.73 7 5/8 gears, which should be 2 series. I want to know if i need the ring gear spacer of not.

On the 373 gears it says GM 41:11, so i assume that they are original 3 series carrier gears. I just want to make sure before i buy the ring gear spacer.

Sorry you wil have to tilt your head

Posi Unit

373 Gears

your gears look like 3 series... if you compare the size of the 3.73's to the 2.73's on that posi unit, you can see how much thicker the 3.73's are... so i believe that you will have to have a spacer...

Here is a known-to-be 3 series posi carrier, for comparison. You're looking for .300" difference in the ring gear flange location; the 3 series would be that much closer to the center of the carrier than the 2 series.

Looks to me like yours is a 2 series. Look at how much "taller" the supporting ribs on the flange on mine are, and how much farther the flange is from the carrier bearing.

Ok so a different way, the bolt flange should be .300" closer to the bearing on the 2 series then on the 3 series. Because that is what it appears to be on the 273 posi.

Yup, because the pinion gear is larger on a 2 series gear set, so the flange has to be moved over toward the outside. So the 2 series flange on the backside (toward the bearing) should be much flatter, where the 3 series is taller and more cone-shaped.

Awesome thanks RB, you truly know it all, thanks again. Now its time to order a ring spacer.

One more question, when i get the ring gear spacer, everything should just bolt right up, correct? I won't have to set up the rear or anything again will i?

I don't know about all that; "all" is a pretty big word. I've just had lots of opportunity to observe stuff, and try to keep open eyes and an open mind about what I see.

Yes, it *should*all bolt up with a spacer. The only thing you might need is a set of carrier shims.

Here's the 2 pics side by side, for comparison. I think the difference is fairly clear. It's great that yours and mine are the same brand and all, the only visible difference (besides yours having a gear mounted on it and mine not) is the location of the flange.

I wound up with two differant ring gear spacers and there was like .009" differance between the two. Deffinately get some differant carrier shims. And make sure that the spacer comes with bolts, my first one I bought didn't and you can't just go to the store and buy those.