This seems like something alot of people talked about before, but I can't find anything with search. So which ones is better for what applications? What would you rather have?, or which one did you pick if that the case? psot as much info about both as you have, I'm posting this so I can learn about the both, so please help me in my knowledge deficancy

 

i want to put a 9in in mine. my dad is giving me his from the 69 cyclone he just picked up a couple months ago. he is goin the grand national floater route.

 

But WHY do you want one?, what are the benefits of that over a 12-bolt for your setup, or why would a 12-bolt be better for another setup? or even the same setup?

 

As far as GM rears are concerned, the 12 bolt is the strongest piece available. However, the Ford 9 in. rear is even stronger than a GM 12 bolt. It also doesnt have C clips, so you dont have to worry about the axles falling out. Im my personal opinion, the Dana 60 rear is the best all around rear. Just as strong as the Ford unit (maybe stronger), no C clips AND less frictional drivetrain loss than both Ford and GM! Thats what I know about those rears, I hope this helps you.

 

i want to put in the 9in for easy gear change and strength

 

Both are equally strong. The 9" takes a few more hp to turn the gears but not enough that anyone would really notice. About 5 hp at the most.

As mentioned above, the 12 bolt uses c-clips to hold the axles in. You can get c-clip eliminators but on a street car they have a tendency to leak after a while. It's harder to change gears on a 12 bolt but if the car is set up properly the first time you don't need to change gears.

My race car uses a 9" just because it was simpler to install. At the altitude I race at I use 4.56 gears. If I go to a lower altitude track I have another center section ready to go with 4.30 gears. I need the different gear because without it I would run out of track before running out of rpms. Different altitude makes a big difference on the performance of the engine.

Some people say you can drive to the track with 3.50 gears, swap the center section for 4.10's to race then swap back to go home. I have yet to see anyone do that. It's not as simple and easy as it sounds when you're at the track. If you're driving the car on the street with 3.50's and need 4.10's for the track then the 3.50's are not what you need on the street. You need 4.10 and an overdrive.

9" parts are the cheapest so anything you want to do to the diff will be cheaper than a 12 bolt. If you wanted to switch from 2.73 highway gears to 4.10 race gears, they'll swap on the same carrier. A 12 bolt needs a different series carrier as the gear ratio changes.

Choosing the diff becomes more of personal preferance since both are just about equal. Only in racing classes like Stock Eliminator do they say a GM vehicle must have a GM diff so they use a 12 bolt.

GM produces stronger diffs. Many 3/4 ton trucks and my 1/2 ton 454SS use a 14 bolt 9 1/2" ring gear. The larger 14 bolt (1 ton's) use a 10 1/2" ring gear.

 

pick up a copy of chevy high performance it has a good article on this very subject.

 

I 2 also read the article in Chevy Performance... It was good, but in the end it was said that it's pretty much up to the driver. If you have a regular street rod (daily driver/racer) a car that sees some drag service, then go with a 12"... However, for those who choose to race more than drive on the street usally go with the 9" due to the factors already listed above (cheap parts, easy, strong, fast install, etc...). The 9" often times sees more time in all out drag cars, as where the 12" sees a little of both. Both rear ends are great IMO, so really you need to ask yourself, what do I want...

Now, lets talk cost... Can anyone point me to a good site that sells (cheap) rear ends, both 12" and 9"....? I would ideally like to spend about $1200 and no more on a rear end.

Thanks for the info!

PS I know for sure the dam stock 7.5" auss rear ends will NOT, I SAY AGAIN NOT hold up to anything over 400HP with the same ratings in the tourqe area. I am not interested in learning this the hard way. (after spending money on gears and possi for my dam weak 10"......) Time to start over again, this time with something rated a little higher.

 

There is only one good reason for the ford rear. If you race then you should get the nine inch for easy gear changes.

 

Ford part...BLAH.

 

For $1200 you're not going to get a complete bolt-in 12 bolt or 9". You can get most of it (housing and axles), then install gears and carrier that can be purchased cheaper locally.

I ran a beefed up 10 bolt and ran low 11's with it. Slicks, 3800 stall converter, TH350 and a big block. The only reason I switched to a 9" was when I added a transbrake to a new TH400 tranny.

Get aftermarket 28 spline axles, good posi, good gears, solid pinion spacer, weld the axle tubes and get a rear cover like LPW with the bearing cap supports. The weak link is still the tiny ring and pinion but it can be made to take more abuse than most people will give to it

 

So the most damage I can aspect is ring and pinion? I thought the Richmond set would hold up a lot better than the stock stuff. I may try that. I may beef it up and race on it until it gives out or I get sick of replacing pinions and just up grade to something thicker.

Thanks