Hey everybody,

I've been holding out forever trying to find a 3.42 posi w/disc brakes.
I called this guy who parts out a lot of them and he said he had one.

I took off the cover and saw the springs, so I thought it was posi.

I turned it where the driveshaft bolts on and it took about 3.5 turns to get the rotor to turn once, so I thought maybe it was 3.42.

I get home and looked at a 2 vs. 3 series thread on here and realize it's probably series 2 non-posi.
However, the other side does turn at the same time. This rear was tested off the car by itself..

I thought I tested it wrong so when I got home I turned the passenger rotor twice and got just under 5.25 rotations from where the driveshaft bolts on. I divide that by two and get 2.6xxx???



If you make the pictures bigger you can see: Richmond 80-0452-1 L (and) 5 8620
Also in another pic. there's: 0910---> <---13
In another pic, someone etched something into it...
http://s189.photobucket.com/albums/z...2000/Firebird/


In this thread on post #3 guy says Richmond 80-0452-1 is part of a set P/N 49-0046-1, which are 3 series, 3.73 gears, and 27 spline.
https://www.thirdgen.org/forums/part...stock-3-a.html
Now I'm very confused!!!


It has aluminum calipers and 11.6" rotors.
The bolts were counted and it is a 10 bolt.

UPDATE:
I counted the teeth on the ring and pinion. 41 & 11 is what I counted which I believe comes out to 3.727272, so I guess mystery solved. I got 3.73.


3 Questions:

1- What's up with the carrier? Is it a series 3 or series 2 with thick gears?
2- Is it Posi?
3- Another guy said this ring is part of a set that lists as 27 spline. Would it be likely this ring's also part of a different kit with 28 given the aluminum calipers and 11.6" disc?


Thank You,
Shawn

 

since you have the cover off already count the teeth on the pinion and on the ring gear then divide the big number into the lil number.

Its a cone type posi unit.

 

Edit:

I found the pinion down low behind everything else.

Got 41 on ring and 11 on pinion.

-Shawn

 

The ring is the big round one with richmond on it.
The pinion is what makes the ring gear turn. It sticks out the front and bolts to the driveshaft.
do a google search for rearend parts and learn the names of the parts your looking for and at.. it will help you.

 

So I didn't want 3.73's, but now I got em.

Would it be too much for a 305tpi 5 speed?

I have the cat back magnaflow. Gonna get headers and port heads.

I've read that 3.73's a little much for 700r4, but I'm guessing T5 would work a little better?

Thanks for the quick replies TTOP350.

 

might help off the line at the expense of higher rpms at freeway speeds... overdrive ratio in 700r4 and t5 is pretty close to the same

 

My T5 is from a '92 305tbi so it should have the .63 5th gear which I'm hoping will help a little.

Not being the richest man in the world, I think I'll see how it rolls first and buy new gears only if 3.73's are too much. I really wanted 3.42's, but I was ignorant of what gear was pinion when I bought it. I was looking in the carrier...

Speaking of...is my carrier series 2 or 3? and how do you tell just by looking?

Thanks Fellas

 

You can adapt a 3 series gear to a 2 series carrier with a shim, but most likely you have a 3-series carrier. Generally if it's 3.08+ numerically, it's a 3-series carrier, below that is a 2 series. It may be 3.23+, not sure, but with 3.73's you're way up there.

If I were you i would go T56 hunting. The 3.73's are fun to have.

BUT... if you really have a .63 overdrive (wouldn't be too hard to find out if you have an accurate tach... factory one is NOT) you'll be a 65mph at 2000 RPMs. That's perfect.

 

if the factory axle tag is still in place the numbers should tell you the original ratio if it was a 2.73 it is probably a 2 series but a 3.08 and up would have the 3 series. the main difference is the thickness of the ring gear. unlikely its still there after 20+ years though

 

Does anyone make the prebent brake lines and T box for the rear?

The ones on this rear are rather corroded in some spots...

Also need drive and driven speedo gears now. Getting one gear that can stay on if I do 3.42 later would be best. Running stock 245/50-16.

 

Part number here:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

JamesC

 

The spline confusion:

27 is the # of splines on the pinion, where the yoke goes onto it.

26 or 28 is the # of splines on the axles and the side gears in the carrier.

All rears of this model have 27 on the pinion.

Roughly, 89-back have 26 on the axles, and 90-up have 28; although the dividing line in reality isn't quite that clear-cut.

You do in fact appear to have a 2 series Auburn, not the "hi-perf" aftermarket one, but rather the stock one; and the "special" "thick" 3 series gears to take up the missing 3/8" or so that you've seen me post about elsewhere.

You can tell which carrier series you have, as I've posted repeatedly elsewhere complete with pics of YOUR EXACT MODEL, by the shape of teh ring gear flange on the side opposite the gear. Since the pinion for low-ratio gears is so much larger than the ones for higher ratios, the ring has to be moved farther away from the pinion for the 2 series setup, making that flange look flat. For 3 series, the pinion must be closer to the gear, making that part of the flange look cone-shaped, roughly 3/8" in height.

 

JamesC -
Wow, that link was spot on and awesome. Fineline's website looks a little dated though. Their calendar show dates don't seem to jive with Carlisle, PA event dates for this year. I'm gonna call tomorrow and see if they're still in business.

Sofakingdom-
You're pics were the ones I referred to in earlier post. I was making sure it was that shape that distinguished the two. Your explanation on the spline confusion also helped a lot.

Would the "cone type posi" (as 350TTOP mentioned) and series 2 carrier be a factory made combo on 89-92 pbr's? (2.73 & 3.08 come with pbr's?)
Everything appears stock, so I'm curious if it's likely all stock, minus ring and pinion.

Also, this rear that I bought has it's share of flakey surface rust, but I do have my 2.73 drum setup which looks better. Now I gotta see about swapping new stuff over vs. scrubbing and painting the one I just bought.

This site's exceptionally educational. I'd probably give up and part it out by now if it weren't for these forums. I look up most of what I need on here. Not sure where the Hayne's manual is anymore...

Thanks Guys

 

"cone type posi" refers to the 9-bolt rear; last year of that was 89. Not alot of those in the world with the 89-up brakes. Yes some were 2 series; most notably, the ones that came with 2.77 gears, which is the majority of the TPI/auto combo cars.

Yes yours is probably all stock, except for the gears; probably came with 2.73 gears. Probably 60% odds or so. Then about 25% would have been 3.08, probably 10% 3.23, and 5% or less 3.42. Very approximate of course.

Yes 2.73 and 3.08 came with PBRs, as well as 3.23 and 3.42, in the 10-bolts. 3.08 would be very unusual because that ratio mostly came only in 305 TBI / T-5 cars, very few of which would have been ordered with posi, as it's mostly pointless in those (besides that, if someone was interested enough in "performance" to pay extra for a posi, they would have started out with a better drive train than TBI to begin with). In the 9-bolt, PBRs would mostly have come on 2.77, 3.27, or 3.45 geared rears, ONLY in 89 though, with 2.77 being far and away the most common.

 

sofakingdom-

Did you check out the pics in my link? TTOP350 says it's cone type posi, which you say references the 9 bolt, yet I counted 10 bolts on the ring gear. (Not the cover...lol)

Hmmm....

 

Right: the Auburn that comes in 10-bolts is a clutch type posi. So the "cone type" description isn't really applicable to those.

 

Take a gander at his link above. I don't see any notches for the clutches. All I see is a cone hiding under the side spider gears. I don't think its a clutch diff.

 

He also did the common mistake of counting the bolts on the ring gear not the cover. It could be a 9 bolt.

 

I said "I counted 10 bolts on the ring gear (not the cover)" because I read that it's a common mistake to count the bolts on the cover.

This should be clarified by someone for the sake of future readers...it doesn't matter in my case because the gear and cover are both 10 bolt.

Thanks

 

9 bolt, 10 bolt, and 12 bolt are all identified by the number of bolts on the outside cover. There are different size 10-bolts, but the 7.5 10-bolt is what we are using, very common. The second gens used an 8.5 (I think) 10-bolt, much larger ring gear. But it's stil a 10-bolt design, just larger.

Aftermarket 9-bolt cover:


Aftermarket 10-bolt cover:

 

The (thirdgen) 10-Bolt FAQ covers the issue.

JamesC

 

fyi 3rd and 4th gens all use the 7.5" except some of the 3rd gens that got the borg warner 9 bolt... in fact a 4th gen rear end is an almost direct bolt in has the correct mounting points for torque arm/lca's/shocks etc. but requires a wheel from a 4th gen or one with the proper backspacing for a 4th gen since the flange-to-flange width is greater.

 

Not sure 3.42:1 or 3.08:1 are that scarce, because first of all, posi isn't just drag race performance, it's also winter traction in snow-heavy states. And in that whitre mess, even a 2.8 can need a posi. Second, all the '88-up V6 / T5 cars were 3.08:1, and all the '85-up V6 / auto cars were 3.42:1, not just LB9 / T5 Thirdly, I did go to the trouble of putting a used Auburn in my '91 RS LO3, with the 2.73:1 gears, and then managed to make twin black stripes on dry pavement from a dead stop. Yes, I had to use both pedals to get started, but a pure-stock LO3 / 700R-4 / 2.73:1 / 235/55R16 car can do elevenses, as they're called now.