What rear gears should I rum???

[viperjesse]

I'm planning on a 502 in my 69 with an M21 trans. What would be a good rear gear ratio in a 12 bolt ? I won't be driving on the highway, basically around town stuff.
I don't want to be too low but also want a good launch?
Thanks in advance
JZ

[Pete R]

3.73-4.10 is a good range to look in. I have 3.73's and at 65 they turn a little over 3k. My 68 has a small block.

[z28pete]

The 502 should give you a good launch regardless of gear ratio, but a 3.73 should do the job. With the torque of a 502, make sure the car is stiffened up, and the drivetrain up to the task. Should make an awsome street machine.

[viperjesse]

Thanks Z28pete.
Can anybody give me a sequential list of the gears from high to low?
I can built a car and engine but haven't learned alot about rear gears.
Thanks guys
JZ

[Pete R]

Standard 12 bolt ratios for a 69 Z28 would be 3.73 (standard) with optional 3.55, 4.10 and special order 3.07 or 3.31 gears. I've seen racers go as high as 4.56/4.88 rears, but with a stick, you'll spend all your time shifting in normal driving. Like I said, 3.73s are low, but a good compromise between off the line speed and having top end(You'll barely be able to break 100 with the really low gears)

[Ryatt-Motion]

I would go no higher than a 3:42 with a 4-speed. I am actually running a Richmond 4-speed which has similar numbers in gears as an M-21 and those were the gears their tech advisor advised me to run. Now if you had a 5 or 6 speed, then hell yeah do the 3:73's.

[Pete R]

3.73's were the standard ratio with a 4 speed in 69! Going with 3.42's only gets you lower RPM at cruise speeds, so if you're not planning much highway driving the 3.73's will be fine. I have a 4 speed now, but I'm planning on swapping for a 5/6 speed somewhere down the line. BTW- We didn't talk about posi carriers. Not all 69 12 bolts came with them and with this much power, you'd better have one.

[viperjesse]

I absolutely plan on a posi carrier. I'm also looking at Curries Ford 9" rears made to bolt up to a 69 Camaro. Cost will be about $2k but the 12 bolts I'm seeing are around that price also.
Anybody know of any other suppliers other than Curries???

[VETTEpwrdZ28]

i wouldnt go 9'' , id go with 4.10...cause i wouldnt wanna hack up the body to fit a 9"

[FANTA-Z]

They make the 9" to bolt right up now a days so you wont hack anything up. I thought Strange made a setup for those cars as well. I would run
3:73s as well.

[68Blue]

Viper.

Have you tried moser? I bought one back in april 04 for my 68 camaro, I dont know how you are set up as far as motor and tranny. But my rearend is set up for me to run a BBC and on spray the rearend is rated to handle about 1000 hp. The rearend has 35 spline axles, 5/8 scree in studs, spool, 3.89 gears, back braced, and a fill hole welded on top. I pais $2500 including shipping. If you are not going the BIG hp route the price will be alot cheaper.I have pics. of it if you need to see what it has.... Thanks LOL

[Ryatt-Motion]

They make the 9" to bolt right up now a days so you wont hack anything up. I thought Strange made a setup for those cars as well. I would run
3:73s as well.


Precisely!! Moser and Currie do a direct bolt in, infact their signature 12 bold rear ends feature Ford axels and axel tubes.

[Pete R]

I still think my corporate 8.5 inch 10 bolt was the best choice. It's lightweight (as rear ends go), can handle lots of HP, came with disc brakes already on it, and with a 3.73 posi still came in under $900 newly rebuilt.....