The Dodge Challenger Message Board

after 2 years, I finally finished my restauration, but after a nice test-drive to the MOT-test(i've passed!), i found out that my rear diff. bearings are worn-out(found a lot of metal when i changed the diff oil), i also discovered that i need some sort of Limited Slip diff... , i was thinking to buy a complete third member, any recommedations?
as for the axle ration, i don't know what ratio i've got know, should i change to a high or low ratio for better acceleration?
Do most challengers have a 8 3/4 axle?or a dana 60? should i chose a 489 or a 742 case?
my tire size is 275/65/15

thank you!

david

You need an 8.75 inch diff unless you have 500+hp and a 4-speed in which case get the bigger Dana.

If you race the car go for the 489 version if you can but all of the 8.75 axles are pretty strong really.

Randy's Ring & Pinion is a popular place to get all your parts from.
http://ringpinion.com/default.asp

As for what gear ratio to use. Well that is really down to how you use the car and what cam is in the engine.

If gas mileage is of no concern use a 3.55:1 ratio. It the engine has a performance cam you might be better off with a 3.73, 3.91 or 4.10.

If you tell me your exact cam spec, what engine you have, what speed you cruise at when on the highway, i can tell you what gear I think you should be using for best all-round performance and mileage.

dave,

i've got a 360 with edelbrock performer rpm cam and a B&m torque convertor(2400stall), the rest of the engine is also modified... it should reach 400hp/390ft-lbs at 4500t/min(+/- according to my dynodesktop)
if i'm driving on a highway it will be below 70mph but i'm not planning to drive lots of highways, its just for some fun at the weekend and maybe a 1/4 mile...

Stick a 4.10 gear in it then and rock and roll!

dave-r wrote:Stick a 4.10 gear in it then and rock and roll!

okay , will do!

thanks dave !

Gentlemen.
Does anyone KNOW if you can substitute a 8-3/4 to a DANA without modifying the propshaft ??

Also,...are there any particular geometry one should ask for ?....or are the rigid rearaxles always straigth ??

I plan to run on 275/40R15

No, I belive the propshaft will have to be shortened somewhat to run the Dana 60. Keep in mind the yoke on the third member as to what you must use on the propshaft. In other words the propshaft yoke must mate with the yoke of the third member, many use the Spicer 7260/7290 series for your application. The 7290 is larger and stronger. Either www.manciniracing.com or randys will 'hook' you up!