probably shouldve asked this on the tranny/rear end board, but seems like theres a lil more action here.

im building up a 440 in my 69' RR, and i need help selecting/finding a rear end. since im gonna building the engine to 600+ HP an torque i was thinking of going with a chrysler 9-1/4".

what do you guys recommend? and where can i find a new one online or one in decent shape. also what is the difference between running a 3.90 gear and a 4.10? and the difference between c clip and a dana then obviously the shape of them. sorry for all the questions but im completely lost when it comes to differentials.

 

N -

The 9 1/4" is basically a truck rear, but I've been using one on a 500+ HP motor in a B-Body for about 30 years.

More common are the 9 3/4" Dana 60's and the 8 3/4"s. With that kind of HP, the Dana might be a little safer, but both are used.

You have to figure out what you are going to do with the car. The gear ratio for a drag car should be set so you are just under your redline as you go through the traps.

For a street car that will get very little highway use, then 3.90s or 4.10s will work. You probably won't be happy with that on the highway for any length of time, though. For combined street/highway, 3.23 or possibly 3.55 are more appropriate.

There are calculators (Summit has one on their site) that will give you RPM based of diff ratio and tire size. That might be a place to start.

Then you have to factor in trans type and stall if you're using an auto.

A little more info would help.

Archer

 

Thanks archer. Here's some more info if it helps.

69' roadrunner
Engine:Stock 440 I plan on building to a 505wedge,then will probably supercharge it later. I'm restoring it from the ground up so everything on it is gonna be either new or refurbished, it's just a roller right now but I have alot of the parts already.
Transmission:I have the original 727torqueflite, idk if I should keep it or go with a modern tranny, I'm gonna keep it automatic though.
Suspension:none yet

I plan on making it a high performance street car and keep it on pump gas, so yea street driving and some highway driving. So should I go with a 9-3/4" Dana 60 with 3.55s then? Where could I find that like a dodge ram out of pull a part, Or could I get a new one online somewhere?

I don't even have the driveshaft for the car so nothing is set in stone yet, I'm open to advice.

 

If you're planning on doing this type of stuff, a Tremac 5 or 6 speed with a Dana 60 with 3.73:1 gears is the way to go. Good for racing, good for highway and gas mileage, great for street cruising.

I run a 8 3/4 with 3.91's in it. Street car. I can and have driven it 60 miles one way to the track. Runs 11s all day long. 60 mph at 3k on the freeway

 

The Dana 60 axles in the trucks are 8 lug and full floating. You can get hubs to convert them to a 5 on 5.5 lug pattern if you want but you'll have to redrill some 3/4 ton rotors to fit and then go with a disc brake setup. Not to mention, you'll probably need to cut or lengthen the axle to fit under the car correctly.

The Dana 60 axles in the cars are usually 5 lug and semi-floating.

You can find Mopar Dana 60 car axle on ebay, maybe craigslist in your area too.

 

Finding a good B body Dana would be the way to go. You can also go to Strange engineering and have anything you want made!! There were lots of 1/2 T trucks and vans with the 9 1/4 rear that could be modified to fit
http://www.spohn.net/gadwords/?actio...FeaDQgody2oA2Q
or
http://www.moserengineering.com/comp...ssemblies.html

You want to convert it to the BIG 1350 ? U joints too...

 

If your serious about the level of power I think a 9.75" is warranted. I have read and know of guys who have put alot of money into 8.75" and wish they had started with the larger one or have gone to a pro 9" Ford.

My opinion is that if your going to that level get a fabricated housing or new 9.75" built exactly the way you want it with all bracketry welded on to suite the suspension you decide on and have total piece of mind back there. It will be expensive but should last a very long time. We like the Strange company.

 

a 600 hp 440 is barely streetable. are you building a race car?

 

hes right my brother had one its crazy on the street that kind of power
his was in a dart
for instance he had too run 4 mufflers 2 turbos 2 glass packs 2 1/2 id pipe the car would rattle the house.................... and at the intersection forget it solid core wires u new everybodies radio is wining and when he would hit it all........ feather footing or all smoke and when it would shift from 1st to 2nd at 80 mph it was like being launched out a frigin cannon hardest shift ive ever felt to this day and it would jump 2 car lengths on the poor third gear jamming car quickly slipping away behind us and if the car broke loose wow.
hmmmmmmmmmmmmmmm
scratch that
hehe
mabe try 500 hp with a 200hp boost and a six speed CHECK OUT TCI TRANSMISIONS for those top speed runs of sayyyyyyy 220 260 maybe 300 who knows if you ever get a chance to drive through say the state of Montana
its a milage gear but check out the rear end that cam out of that beast total stock he got it out of a junk yard about 25 years ago its waiting for that next ride

 

Barely streetable? My buddy has a 572 crate in his camaro which is 650hp stock and he gets 10+ mpg. Besides Nelson racing builds 1500hp+ "street cars" so 600horse out a 440 is nothing.

 

Friend had a 500 hp 440 in a 71 Charger Was very docile until you stepped on it so 600 is street able Not something I would drive cross country

 

wat he said i agree go for it but go for top speed...... 6 speed trany with 1500 hp just smash the two hundred mph mark