Hey, Im Gary, 24 from the bay area. i have a 79 trans am that i am overhauling and i am a true pontiac lover. all those speedshops that keep telling me to put a chevy in my tranny can eat my dust when im done. anyways i am concidered the first owner since my mom bought it brand new, but it sat for like a decade in the garage before i got to start on it. ill post pics as i go along. curently it is stripped to the frame. i want to swap out my rear end but i don't know whats best, but my main goal is to convert to disc brakes in the back and increase my 1/4 mile times. any suggestions???

 

Im guessing you have the 403 Olds motor. I would swap this for a Pontiac 400 or any motor of Pontiac. To add rear disk breaks would be very simple and it done all the time. If you want good performance from a simple rear end swap, try 4.10, although a 3.73 would be much easier on gas and still be better than stock. However, if you switched from a Olds motor to a Chevy, you need a new TH350,the bellhousings are differnt. Olds and Pontiac use the same though. Be sure to replace your rear shocks with something like WS6 or stronger rear shocks and springs if yout going to be racing because of the strong take offs these cars have. SHould help with wheelspin too.

 

Gary, if you want bolt in rear disc brakes for your 79 see if you can find a factory WS6 rear end for your car. 79-81 cars with the WS6 option came from the factory with discs. The calipers on these weren't the greatest though so look accordingly. Another option is the rear from the 77-79 Cadillac Seville. Same 10 bolt rear with factory discs but the bolt pattern on the axle is 5 x 5 rather than the GM standard of 5 x 4.75. Also uses leaf springs and will bolt right in. If you're going to use a wheel like a Weld Draglite with its multiple bolt pattern though its no problem. Another option I'd recommend to you would be to get ahold of a circle track catalog from Speedway Motors in Nebraska. The have a lot of different disc brake kits available. There is a kit that has bolt on caliper brackets for any rearend with 3" axle tubes. The calipers that you want to use with this setup are the GM calipers that came on the"metric" cars like the 78-88 Monte Carlo, Buick Regal, Grand Prix, & Olds Cutlass. These are also known as the "G" body cars. For rotors Speedway will have a selection for you to choose from or else a rear rotor from a 92 Z28 will go right on with no clearance problems.If you want to go with the ultimate, the Ford 9", see if you can find a differential from a Lincoln Versailles from 75-79. A Versailles is a fancy Ford Granada. These came from the factory with disc brakes in the back. These were also leaf spring cars and with a little careful massaging of the leaf spring mounts they will fit in. You will also need to get a WS6 specification proportioning valve so that your brake bias between the front and rear stays where its supposed to.

 

I did the WS6 rear-disk brake conversion about 18 years ago when I was about your age, crazy about my 'Bird, and didn't mind spending 16 hours a day underneath my car. I got the whole rear axle, T/A leaf springs,brake booster, and master cylinderfor about $300. Getting all of these parts from a wrecked T/A is harder now, but not impossible, and will make the conversion much easier.

The GM 8.5 in 10-bolt is alot stronger than alot of people give it credit, but beat on it too hard and those C-clip axle retainers will go bye-bye along with your alxe and rear tire. The GM 12 bolt is alot stronger, and you can get aftermarket disc brake setups with the GM 5 bolt x 4.75 bolt circle. The Ford 9" rear end is even stronger, and has the advantage of a removeable center section that holds the ring and pinion (great for drag).

BTW, what kind of trans will you be running?

Geno