I get many inquires about 9 bolt parts and my reply to Alkim's email (posted above by Alkim) represents a majority of them.

Yes, a 9 bolt is stronger than a 10 bolt.
Yes, a 9 inch is stronger than 9 bolt.
Yes, a 9 bolt is more expensive than a 10 bolt.
Yes, a 9 inch is more expensive than a 9 bolt.

Don't forget about a drive shaft, drive shaft length, u joints, brakes, brake lines, ..... when looking at a cost comparison.

I believe (and market) the 9 bolt as an intermediate level solution (both in terms of cost and strength (fyi - book mark this post and come back one year from now and read this again )). I have been running my 9 bolt (completely stock) for over 4 years now behind my 500hp/520lbft big block (1.72-1.75 60 fts) with no problems.

My business site has more information on the 9 bolt ( www.diffsolutions.com or www.9bolt.com ). My personal site at www.koolmeister.com has more information on my car.

We are also developing components for other differentials as well (hence the new name of Diff Solutions vs 9 Bolt).


Hope this helps,
Miles
Diff Solutions
www.9bolt.com

 

Yeah, hi. I have the 9 bolt. I also have a pair of Nitto's that I was scared to use in fear of breaking the rear. But by what y'all are saying I should have absolutely no doubt in my mind that it would be fine to run them. Right? Thanx for the info.

 

Rage -

You sig only mentions the flowmaster as your mods. flowmaster + nittos = no problem for a 9-bolt. You have quite a bit of room for more mods too.

 

You could also get 3.45 gears on a G92 305 TPI 5 speed car in 88. I know because I have one.


And Black Sunshine/ 00SS the brakes would bolt up just fine, but wheel spacers would be needed to run it on your 4th gen.

 

That is correct. My statement is only true for L98's. Sorry for the mis-information.

 

Just wanna correct something, no 3.70 gear was offered in the Third Gen. I recall the poster not being sure.

 

Yes, it was. The 85 Trans Am with the L69 engine, 5-speed, and G92 option came with a 3.70 9-bolt rear end. The 86 Trans Am with the same options might have it, as well.

 

If the statement regarding the 3.70 is true, then this table needs updated:

http://www.thirdgen.org/newdesign/tech/techdb.shtml

The guys over a third gen will need more than someone's word on this. They will likely want the VIN, RPO's for the car and probably a picture of the stamp on the ring gear (which indicates the ratio).

 

I haven't seen anything ever saying there was a 3.70 gear in a Third Gen. You're gonna have to say where you're getting that from.

 

Check the History board or the General board at http://www.thirdgen.org/ There are people there who claim to own cars with stock 3.70 rear ends.

 

I don't think they are right.

91Z, you switched to 3.70's?? I thought the best all around gear for TPI was 3.42's. Do you like them??

 

I cannot speak about Firebirds as I only know Camaros. The fact is the 9-bolt was used in the following regular production applications:

1987
3.45: 305 TPI w/5-speed and G92
3.27: 350 TPI
Note: G92 was NOT an option on the 1987 350.

1988 - 1990
3.45: 305 TPI w/5-speed and G92
2.77: 350 TPI
3.27: 350 TPI w/G92

People say the 9-bolt is stronger than the 10-bolt. I know this was GM's thought when they introduced it. What I can't help but wonder is why GM discontinued it in 1990, even as power increased year by year. And why isn't it used exclusively on fourth gen LT1/LS1's if it's stronger than the 10-bolt? Does anyone know?

 

Back when I had my 84 Z28 HO 5spd/3.73 rear. My neighbor had bought a 85 HO 5spd and his came with the 3.70 9 bolt.

I went through hell trying to say that to the f-body list back in 96 or so. Nobody believed me and said it was a 10 bolt. I think I know how to count, at least up to 10

 

I cannot confirm this. However, I have been told that the 9-bolt was phased out due to the cost that they added to the price of the car. It is my understanding that the 10-bolt was beefed up (splines, maybe) in around 1990 to allow GM to eliminate the 9-bolt.

This is what I have been told.

 

The 9 bolt is a lot stronger than the 10 bolt. I don't think a 10 bolt would've held up to the 1.6 launches I was doing with my car. Not a hint of anything wrong back there.

Of course that was with the stock setup. Now that I have a bigger stall, I can't get better than 1.8