So I've actually had this car for a year and always thought it was the standard 10 bolt w/ 3.23's. Today I was replacing the rear bumper and realized what I actually had. So I'm assuming someone previously swapped this in because I didn't think that they started showing up until around 89? Is that correct because my 89 Formula 350 had it. But it does say 3.27 an the P/N is 10032270. crazy....

 

85 was the first year of the BW 9 Bolt, and I believe 89 was the last.

Misread the tech data - my bad

 

I had a 1985 Trans Am with the PHS documentation to go with it. According to original owner the rear end was original. It was a Borg Warner 9-bolt. It was a G80, GU6, J65 car. I was under this car not too weeks ago before I got rid of it. I noticed it while I was pulling parts off of it.

 

Yes, TA only in 1985. No Z28/IROC-Z yet.

 

The BW 9 bolt was first on 85 TA's, the 3.27 would have been the optional gear for that rear. The 2.77 was the standard gear with the 9 bolt that year.

 

Wow so it was normal in 85 TA's. I had no clue. Well thank you all for the responses.

 

I don't know if it was normal, but it was an option. I'm not sure exactly how Borg Warner 9-bolts got into cars vs. 10-bolt rear ends. I know that Borg Warner 9-bolts were common in California cars but mine was manufactured in Norwood Ohio and was shipped to a Texas dealership.

 

I have no clue either. Aren't 9 Bolts suppose to be somewhat stronger? I know they are more expensive to repair though.

 

I've read opinions on either one being stronger than the other. Unfortunately what isn't a matter of opinion is the lack of parts and the cost of upgrading or replacing parts on the 9-bolt. They are much less common.

 

I want to think it was standard for certain engines on the TA... For some reason the HO and the TPI i suspect are the fortunate cars to get the rear axle.

BTW, The axle installs just like a 9 bolt... I do not think that it was a stronger axle as much as it was more efficient, and there was less Loss of Horsepower, which in turn improved Fuel economy... That's what I have read...

 

The tech data pretty much says it all... Most 85-89 Trans Ams, and 87-89 Formulas came with the 9 bolt.

As far as stronger, that's the rumor... But really, what good is additional strength when the parts in circulation are worn out, and there's no aftermarket support.

 

That's a good point. However 90+ rear ends got 28 spline axles and better PBR brakes. So as I understand it the later 10-bolts are better still. Essentially they are the same as what came in the fourth gen cars for the most part.

 

Just as an FYI ... If the car was a 5 speed L69 car, then it could have had the 3.70 ratio. I only know of the 1986 TA L69 cars to have this ... 1985 I'm not sure about. Just an odd thing with the BW 9 bolt that 3.70's were available. Similar to the Camaro with 3.73's with a 5 speed L69.

Mark.

 

I'm pretty sure mine was a 3.23 car. It was a 700R4 equipped car as that was the only option available for the LB9 in 1985.

 

There are companies online that sell 9-bolt parts and gears, stock ratios, as well as 3.90 and 4.11 too. I had a few links saved on my other computer, but not on this one. But doing a quick web search, here are a couple:

http://www.justdifferentials.com/
http://www.9bolt.com/

And TA Performance makes aluminum differential covers for 9-bolts.

PBR brakes began in the 1989 model year. 9-bolts got them too.

Yes, 1985 too... '85 and '86 were the only years for the 3.70 ratio.

 

Price out 9 bolt parts, they're out of sight. The important part is 3 series carriers. From what I've seen no one offers a new limited slip carrier for the 9 bolt rear. Better yet since at least 50% (probably closer to 75%) of the production 9 bolts used 2.77 gears, most of the used carriers can't even accept a decent gear ratio. 9bolt.com will sell you a good USED 3 series posi carrier for about $500. While you're there you can get a used 3.70 gear set for another $300. How about a set of PBR backing plates for a 9 bolt? Again, out of sight.

Meanwhile, you can get damn near anything you want for a 10 bolt from any number of sources, NEW for less money. At the end of the day, if you have POWER you're going to twist up that junk, built from used parts, 9 bolt just as quickly as a 10 bolt built with new parts. If you really think you NEED a stronger rear end, the 9 bolt is just an ignorant choice.

 

It is my understanding, that the 9-bolts center section is still in use today, in Australia.

So while there would be higher shipping fees to get the parts here, I think the higher prices merely come from the lack of USA sources & no one has bothered to look elsewhere for sources for the parts.

 

My wifes 85 T/A HO WS6 had the 3:70 BW (or 3:77 never solved that one) The car was one of 1600, maybe less since it was a WS6. Anyway...

9-bolt advantages:

4 pinion design adds beef

Uses a shorter distance between bearing caps than the 10 bolt giving it added strength.

All 9 bolt rears for f-bodies use 28 spline axles.

Pressed on tapered axle bearings; allows the axles to be bolted in instead of using C-clips

The bad: like the above posts - Parts : )

 

Consider that the Saginaw axle was used in several vehicles, I know it was used in the Firebird & Camaro until 2002, in one shape or another, It was also used in the S-10 & S15, Probably the S15 Jimmy and the S-10 Blazer as well. It may still be in use in something in one shape or form, I am not even sure on that. GM is going to an independent rear suspension even in their RWD cars... I want to think that just about everything (car non truck) now uses an IRS, (Independent Rear Suspension) I am not that up on the newer models, but I cannot think of any newer RWD cars with a solid axle.

new Camaro, G8, Corvette for sure use a IRS AFAIK

 

New PBR backing plates are easy to get for 9-bolts(and 10-bolts), and they're not expensive. Ed Miller makes/sells them. And because GM continued using PBR calipers on 4thgens, even PBRs have become more available these days in junkyard cars. PBRs can even be purchased remanufactured(like new) at reasonable prices from auto parts stores. They might even still be available new from GM. So updating the brakes on an earlier rearend is easier than ever.

Not everyone agrees on parts, how they want to spend their money, or on the amount of work they want to do, whether it's about cars, engines, shocks, oil, differentials, etc. If they did, the world would be a pretty creepy place lol. So if people want to keep their 9-bolts, then everything they need is available to them.

Just saying...

 

I'm not saying that everyone should dump their 9 bolts to get a 10 bolt. I'm saying that the 9 bolt isn't enough stronger then the 10 bolt to be worth the trouble for most people to upgrade. I'm saying if I had nothing and had to choose, I'd pick the 10 bolt. I'm not saying the parts are impossible to find. I'm saying it's easier to find 10 bolt parts and they're less expensive. I'm saying that I've owned both, and I'd rather have a 10 bolt. If I'm pushing the limits of a rear end and I think I might have to rebuild it, I'd rather have one I can rebuild cheaper with commonly available parts. Finally, I'm saying that in the event someone breaks a 10 bolt and wants to upgrade to something that'll hold up, I'd recommend going straight to a Ford 9" and getting it over with.

 

I couldn't stop counting how many times you used the phrases "Im Saying" or "I'm not saying" in one post.

 

That was completely intentional to make the point.

 

Yeah but I didn't pay attention to anything else but how many times. That's all I saw in the post until I read it a second time to actually read what you were saying.

 

My buddies, then new, 85 L69 M5 IROC had the 3.70 9 bolt rear.

As far as strength, there is no comparison between the 10 bolt and 9 bolt. The 9 bolt is extremely strong for the size. I was doing bottom 1.6 short times in the TTA and never a whisper out of it. Others were going 1.5 short times before they started to have problems. Very strong little rears. Try doing that with a 10 bolt, ain't going to happen. Yes a 10 bolt is cheaper but if you look at it wrong, it'll break. The 9 bolt will just keep on getting it.

 

FWIW, the GTO used a modified version of the 9 bolt. They never stopped using them in Australia. I would think the Camaro is using a version of it also. DANA bought it from BW.

 

What exactly are you saying or not saying?

Why a 9" over a Dana 60?

btw, my 86 Trans Am LG4 5 speed had a 3.27 9bolt in it.

 

Spend more time reading and less time replying, I already spelled it out. I can't really dumb it down any further.

Why go with anything other then the accepted standard benchmark?

 

Why go with a 9inch over rockwell toploader rear?

 

A reply towards the OP, my 85 trans am came orignally with a 9 bolt, 3.08 gear, nonposi, with aluminum drums