My 89 TA has a 10 bolt drum brake rear end. I have a parts car with a 9 bolt disc brake rear end. Would anyone consider changing to the 9 bolt? Is not the ten bolt a better rear end? All comments are welcome. I am new to the third generation game. Please help.

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Newbie 1989 Pontiac Trans Am w/305 TPI

 

I keep hearing about this 9 bolt stuff also but it goes against every thing Ive learned over the years.
The statement is "9 bolts are stronger and better"
Of course when I hear this I get confused.
Are they thinking (9) as in the fNord 9? If so the ford 9 is a 12 bolt with a 9in gear, not 9 bolt. More bolts= more holding power!
They may have done somthing special with the gears in the 9 but all the 9 bolts that Ive pulled apart "S-10" have tooth pick internals compared to the 10 bolt "S-15" also the ones in my Z28.
It would be nice to have disk all around but if power handleing is compremised it might not be worth the time&money to install.
SSC

 

The 9 bolt rear has a 7.75" ring gear, the 10 bolt only has a 7.5 or 7 5/8" ring which makes the 9 bolt stronger there.

But the big difference is in how the axles are retained, the 9 bolt has bolt in axles like the 12 bolt and F*rd 9" where the 10 bolt has c-clips. 9 bolts hve 28 spline axles where only the later 10 bolts have them (otherwise 26 spline) I don't know if you ever held a c-clip in your hand, but it doesn't inspire much confidence taking a hairpin at 80+ MPH and if the axle breaks at the carrier, it's taking a trip. C-clips are banned from most racing for this reason.

Personally I ditched my 9 bolt because 10 bolt parts are cheaper and easier to find, and with aftermarket axles and posi and the right buildup, i'm sure it's stronger than a stock 9 bolt. Problem's I had with 9 bolts are lame posi action, even after shimming the clutches, it didn't last for long before I was laying down 1 stripe burnouts.

 

The shimming only works for a slightly worn posi, not one that has a ton of miles and/or abuse on it. Once the shim gets to big, other interefences are created. That's why the GM factory manual only allows for thinner shims.

I now have new carriers and gear sets available.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
Currently installing 3.73's into my 9 bolt (YES, it is a 9 bolt & YES they are 3.73's, not 3.70. I currently have 4.10 gear sets and new series 3 carriers in stock for 9 bolts )
www.koolmeister.com

 

I have had an axle come out of the rear end housing twice in my time. Both were with a Ford 9". The only thing holding the axles in are the bearings and a sleeve that are pressed onto the axle. No mechanical connection. At least the GM 10 bolt has clips to hold them in. I think I will keep the 10 bolt drum brake rear end in my car. I don't see that the required work is worth the gain. I thank everyone for their help.

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Newbie 1989 Pontiac Trans Am w/305 TPI