i just got a 277 posi disc rear from a 88 firebird. i took off the cover and noticed marks on the caps,as if it has been worked on. i also noticed the ring gear is really thick. is it possible to get numerically higher ratio gears for the 2 series 9 bolt like on the 10 bolts?

No. To get away from the 277's you'll need a series 3 carrier.

Not that I know of. Probably could be done but only gears I know made are 2.77, 3.27, 3.45, 3.70, and few custom 4.1x's from diffsolutions. Count the ring teeth and pinion teeth. take ring teeth number and divide by pinion teeth number to get gear ratio to make sure what you have.

well i foundout it has 345's in it. so im happy. it came stock with 277's. but aparently its been changed out.

Wow, you are lucky! Thats a great gear and pretty rare. Congrats!

I had no idea the 3.45 was rare, Thats what I have in my 89 formula! Sweet

You wanna see how rare? Try finding one somebody will sell.
I looked for over a couple years for one. e-bay,here,other sites and came up empty. Had to settle for one with 327's.

Actually they are rare cause the only cars that got one were the
305TPI 5 speed cars.

hmm,i pulled it from an 88 transam. but someone else put in the gears,it was 277 stock.

Somebody's put in more than gears. To go from 277's to 345's they would of had to go from a series 2 carrier to a series 3.
So basically that rear has had all it's guts swapped out with the exception of the axles? maybe.

Yea the axles are the same for 9 bolts regardless of gears and carrier series.

so what your all sayin is keep it?

No, You don't wan't that POS rear.
You need to sell it to me.

is it possible to fit a series 3 carrier like an eaton or the slp take-out posi in a 9-bolt?

A series 3 carrier from a 9bolt can go into a 9bolt with a 2 series. I'm not sure what has to be done, or the cost of the swap, but it can be done.

A SLP take-out unit, or ANY posi meant for a 10bolt will NOT fit in a 9bolt, unless someone can prove that statement wrong. I've never heard otherwise.

ya wanna know how rare 3.45 gears are? i called miles for a new set and last he said (2 months ago) he wont be making them anymore. so luckily for me i have a location on a whole nuther rear for extra.
3 series carriers are still avail from miles.

I got a 9-bolt disc out of an '85 T/A in San Diego for $65. The tag on the housing reads "3.70". As soon as I finish my tranny install, I will change to this rear end. Removed the cover and the gears looked real clean.

Are you sure you read that tag rite? As far as I know the lowest factory gears you could get in a 9 bolt were 345's.
I cant see someone swapping gears and then a factory tag also.

I know now no one carries any ratio that I've found other than 370's. Miles did at one time at 9bolt.com but he's getting out of the 9 bolt bussiness.

Yup. 3.70's. Here is a scan of the rear end tag.

wow, thats a first. i thought when i seen a 3.08 borg that was strange but that takes the cake.
the one thing in yuor favor os DTSand randys ring and pinion have replacement gears if ya ever trash one. dang, why cant i get that lucky on my 3.45's

WOW Thats a first for me also.
Whats the RPO code for that ratio?

I have an 85 305TPI auto car that has 3.45's from the factory.

Cool, Do your RPO codes verify this?Are you the cars original owner?
Reason I'm asking is dealerships have been known to replace a bad 10 bolt with a 9 bolt under warrenty claims.
Did the car come factory with a automatic?
I'm not doubting you,It just seems kinda odd.

Jim did the 85 TA your rear come out of have the HO 305?
Biff same question.

I guess since 85 was the first year for the 9 bolt,GM put them in every thing?
Finding a 9 bolt with factory 370's is up there with finding a 3rd gen with a Dana 44. :hail:

I don't remember if it was an HO or not. I do know that it was purple.

When I crawled under the car and read the tags, I couldn't get it dropped fast enough. I had found an axle earlier that was a 3.27 posi-disc but my shed and house burned down in Jun 03. Sifting through the rubble I found the rear end, but it was fused together inside the housing from the heat.

The bone yard had a half-off sale the next week. I had to drop the rear end and hide it under an old dodge Duster until the next weekend. I was the first in line that weekend at 0530. The current 3.70's are in my garage awaiting install.

Here in San Antonio, the bone yards want $500 for that particular rear end.

BTW, the gear code for that ratio is GS4.

Great find, I've never been that lucky with the junkyards around here. $500 for a stock rear,WOW. Or is that for a 9 bolt with 370's? Are they in abundance in TX? If so it looks like I need to make a trip to TX.

Man, I know what you guys are saying... I've only found one 9 bolt series 3 posi carrier around here. I went to pick it up and it had a broken pin going through it, which really messed up the posi cones. Everything else I've found in a series 3 carrier was open diffs from 82-84 Trans Ams. Several were 3.70 ratio, but mostly 3.23. It's almost time to order a new one I think...

So were most 370 ratio 9 bolts non posi?

No clue. Don't know that much about the rear ends yet.

I'm still trying to get my transmission fixed. I believe I have that problem down to a bad Torque Converter.

I'll address the rear end later this year. I do know that it is a posi unit that had disc brakes. I hate drums.

Jim.

My car is a tuned port car. I do not have the RPO's as they where missing from the car when I got it. The tag on the rear lists it as a 3.45 as do the markings on the ring gear. I can find nothing to tell me that the rear did not come with the car.

RPO Codes are G92 = 9 bolt optional axle G80 = Posi Rear Diff

I got mine from Bruce at Hawk's Thirdgen. I was actually looking for a 3.45 rear to go behind my T56, and Bruce thought he had one so I sent him the MO. Turned out to be a 2.77 rear so he offered the choice of a 3.27 or the 3.70 he had just pulled form another car. I figured the 3.70 would be better for the T56, and imagine my surprise when I found out they were the factory gears!!!

FWIW mine is a posi/disc rear from an '85 TA. I did a little research and apparently it's a one-year-gear, that only came in the Ponchos. It seems likely that it came in the 305HO cars, but I can't find proof of it. I paid $350+shipping (430 total.)

the 3:70 gears with the t-56 is a good choice. I have the 3:45 9bolt and I find I am just a little short on gear. when I am doing 55 mph it's never in the right gear. (too high or too low) any thing above 70mph is ok though. let me know if you guys know where I can pick up a 3 series posi for real cheap. (I have another 9bolt I need to setup for 3:70 gears)

G92 does not designate its a 9bolt, my car came with a 9bolt and does not have the G92 option, It has G80 and GH3 which does signify its a posi with 2.77's and 2.77=9bolt ratio.

G92 is not the only option that nets you a 9 bolt. I have every option for 1LE with air but no 1LE option code. Goes to show you there is more than one way to get a certin part. G92 is an option code that gets you several options. Its a package

Can you use gears from an open diff 9-bolt in a posi 9-bolt?

I have a 3.27 9-bolt... but I found some 3.45 gears in an open diff at the wreckers.

I've never tried it but they should interchange just fine.....I know they do on the 10-bolts.

I never knew thier was a peg leg 9bolt??

As long as they are the same carrier series 2 series does not fit 3 series and vice versa