Differential Options

[MT_Mopar]

I am in the pre-plan stages of installing a moderately built 440 motor in my 67 Coronet.

Maybe a trip or two per year to the race track, but mostly a weekend warrior, impress the neighbors setup.

I am checking my rear differential options, below are the stamps on my existing diff.

I am thinking of going with a suregrip, 4.10:1

Is my existing 8-3/4 rebuildable with a replacement 3[SUP]rd[/SUP] member pumpkin in 4.10:1 flavor? If so, do I need to change out my rear axles also?

Looking for feedback on my options, and it is obvious this is not my area of expertise.

Thanks

 

[BeastlyBirdie]

742 is, in my opinion, the best 8 3/4, and is what you have. However, 4.10:1 might not be the most street friendly gear...with a 28 inch tall tire, you would be around 3100 rpm to go 70. So, depending what you are trying to do, you might examine something more in the 3.55-3.91 range, plenty of go, and happier on the street.
As for yours being rebuilt, parts are readily available, check with doctor diff.
Stock axles would be fine.

 

[Cranky]

Cone type Sure Grips can be machined to work very well so don't chunk it into the scrap pile before tearing it apart to see what the condition it's in. Clutch types have an aftermarket/nos parts available so they can be rebuilt and none of the 8 3/4 rears are really bad....even the 41 will do job.

 

[BeastlyBirdie]

Cranky, isn't that a 742, and I thought they were all clutch.

 

[Cranky]

Cranky, isn't that a 742, and I thought they were all clutch.

These days, it's no telling what you got unless it's totally original.....

 

[moparmarks]

From the factory 741/742 cases had clutch packs. 489 has cones.

 

[MT_Mopar]

You guys rock, thanks for the info!

Gonna have IQ52 build me a 440, nothing too extreme, none-the-less, I am sure the neighbors will be impressed! :headbang:

 

[62 Dart Convertible]

You guys rock, thanks for the info!

Gonna have IQ52 build me a 440, nothing too extreme, none-the-less, I am sure the neighbors will be impressed! :headbang:

Someone further up mentioned Dr Diff (http://www.doctordiff.com/). Cass is your man, and in Montana too!

 

[HYRDGOON]

Dr. Diff Dr. Diff Dr. Diff Dr. Diff Dr. Diff...

 

[440ronnie67]

good thread, I haven't done anything with mine either, I do know both tires light up lol. Checked the fluid and that's it.

 

[Moparmatt72]

Dr. Diff is a good place got a few things from them, I got most of my stuff for my Dana build from strange and they have 8 3/4 stuff as well