Just curious, because I havent seen a lot of 9 bolts on here with all this. How rare was this option?

7.75" 9 bolt
Stock 3.70 Posi
PBRs w/ 11.xxx" rotors

the main thing that caught my attention was the 3.70. Ive seen people list it as a possible option, but I havnt seen too many of em around. This guy thought it was a 2.73 so it pretty much gave it away. $100 for rear (caliper to caliper), plus another $100 for new wheel bearings, seals, AND brand new rotors and e-brake cables.

 

Actually, the 3.70 was a dealer installed gear. I have the same rear sitting under my '87

 

Well Im not sayin that its an aftermarket gear, Im just sayin that I havent heard of too many stock 3.70s out there. Most are 3.27 or 3.42 (I think?)

Ive also heard that 89 was the last year of the 9 bolts, and the first year of the PBRs. Is that correct?

 

If it is dealer installed, it's not 'stock'. The 3.70 wasn't offered from the factory and had to be installed by either a dealer or an aftermarket dealer. '89 was the only year for the 9 bolts and PBR brakes on the back.

 

ohh ohh, sorry, I got ya now. I thought for a sec dealer installed=stock. So maybe thats why theres no so many out there.

 

I don't know for sure when the 9 bolt was discontinued, but my Helms 1990 Firebird service manual discusses troubleshooting and overhauling both the 10 bolt and the 9 bolt. So they did have them in 1990.

 

The 3.70 was used in the H.O. 305 Carb Cars with 5-spd's (T/A's and Camaros) from 1985 to 1986. The 9 boly Aussie rear end was last used in the 89 F-Body's.

- Dave

 

Believe the 9 bolt was a Pontiac only axle in 85 and 85. The very few 305 HO 5 speed Trans Ams got the 3.70 ratio. The 82-86 Camaros and 82-84 Firebirds both got the 10 bolt axle. Friend's 84 HO 5 speed Trans Am had a peg leg 10 bolt with 3.73s. The 9 bolt appeared in the higher performance Camaros and Firebirds from 87 through 89. Quite a few people have found original 9 bolts in their 90 models so they could have been using up the remaining stock early in the model year.

 

The best stock 9-bolt ratio was the 3.45.

 

It is possible then that the 3.70 was in the '85 model cars. I pulled my 9 bolt out of an HO 5-speed car and it had the tag (either by the dealer or the factory) with the 3.70 part number and ratio stamped in it.

 

Ahhh, forgot about that one, it is pretty much impossible to find these days as is a nice 3.45. I had a 3.23 9 bolt in my '89 Formula 350, there was also a lower numerical ratio too if I remember right.

 

GS4 was the code for the 1985 & 1986 7.75 DIA 3.70R Gear. The GM part number for the Ring and Pinion is(Was) 10037063.

There is either one of two things with this axel: 1) the 10.75" PBR's were added to an 85/86 axel OR 2) the 3.70 gear was added to an 89 Axel, The second is probably more likely.

SLP used to sell the 3.70 gear kit for the 9 Bolt, they also used to sell the Speedometer gears for the 3.70 or 3.73 axel for the A4 or M5 trans. I bought The Speedo gears from SLP they were only $29 when I got it in 1999.

John

 

According to my Haynes Manual(for Firebirds), the 3.70 is listed for the Borg-Warner axle in 1985 and 1986 only. But it shows it with an 8-digit GM part number, instead of a 3-digit B-W code like the other B-W axles. And Klortho's 10032274 is the part number, available in each year.

And it only shows the B-W axles being available from 1985 through 1989... none showing in 1990 and later. But I've read here on TGO in the past that remaining stock was used up in 1990 models. So there might be some 1990s out there with B-W axles.

 

John, you might want to look at the part number again, the number on the tag picture I put up corresponds to the Haynes manual and other places the 10032274 as the part number for the 3.70 but that could be for the entire rear and not just the gearset, it's hard to say.

 

A friend of mine ordered a carbed 5speed 86 T/A brand spanking new and it had the 3.70 BW G80rear with iron calipers ..

 

My 1985 HO 305 T/A with the 5-speed had a 3.70 rear gear from the factory. I bought it new. The 3.70 nine bolt was used by Pontiac to make up for the lack of torque the engine had compared to the 305 TPI car.

- Dave

 

Your tag is obviously the correct part number and I posted the correct part number from the Parts catalog. Your tag is for the complete assembly, the part number I gave was for the Ring and Pinion set only. I posted it so you could search dealerships for a set... it would be a lot cheeper than buying a complete axel .

John

 

Ahh ok, I figured your part number may be for the ring/pinion set, but wanted to be sure.

 

Buddy of mine had a 85 IROC HO 5spd with the 3.70 gears. This was back when I had my 84 Z28 HO 5spd with 3.73 gears. His car was bought brand new.

 

Wow, lots of good info guys. And from what Im readin, indeed something was swapped out. Im betting it was an 84-86 axle or whatever and the guy put the PBRs on. It was missing a few brake parts, so thats why Im leaning towards that. So I guess its not really rare, but still a decently stout rear Id say. I was wantin 3.73s for the 10 bolt, and now I got 3.70s with discs! Thanks for all your help guys!

 

anyone find a dealership or some parts outlet that can find these parts?? I did a search on one website and a part came up so I ordered it, then when I checked the status of the order the next day it was canceled. I checked out why and it said part was not available because it was discontinued. If this was true then why did the part show up in my search, when other parts I was trying to find didn't. Made no sense to me and I was kind of upset, I was surprised to even see it listed. I don't know if these people use the same database but I've tried many different sites and get the same results. Pretty lame if stuff is showing up when they don't even have it.

 

I got my wheel bearings and seals from ratech mfg. There are some parts that are still at dealers, not made anymore but just overstock and whathaveyou. What kind of parts are you lookin for? There are some other companies IIRC that sell 9 bolt parts, even whole posi units.

 

There is a company that still sells 9 bolt parts. I'll try to dig it up.

 

don't know why the link turned out looking like this but clicking on it gets you to the right place.


Jaws Gear & Axle</title>
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never ordered from them but they list about all the parts you'd ever need for a nine bolt bw rear