Center Section Differential Recommendation

[RenVill]

Please bare with me, I'm not knowledgeable with these things which is why I'm posting this thread.

I'm replacing the rear suspension on my 72 Demon that currently has the full RMS front end, 360 and 727 column auto. I've ordered and received the RMS Street Lynx with 8 3/4 Housing & Axle Package stock width 30 spline. I was informed that I still needed to purchase a center section differential to complete my parts list before installing, minus a custom shaft that I guess I'll just have to go over once the shop installs.

The end goal of the car will have a gen 3 hemi 392 with on the floor stick shift but that wont be for quite some time so whatever I'll put in the rear now, will preferably work with both or at least with the least amount of modification/parts once I'm ready for the modern stuff.

Can anyone please recommend me to purchase a center section that they feel should work with what I have currently and hopefully what I'll have in the future. Any insight is appreciate and sorry for being a noob and asking. Thanks in advance.

 

[33IMP]

What trans behind the gen 3? Number of overdrive will determine best ratio for the rearend.
What works best with a six speed, will result in a lot of highway rpm with a 727. A LOT of rpm.

 

[Dana67Dart]

There are 3 center sections.



741 (weakest, least gear ratio options)

742 ( middle of the road for strength, wide range of gear ratios)

489 (strongest, widest range of gears available)


Cass at doctordiff.com can set you up with what you need.

You can put an ad here, you can look on EBay, Craig's list, Facebook market place

 

[RenVill]

What trans behind the gen 3? Number of overdrive will determine best ratio for the rearend.
What works best with a six speed, will result in a lot of highway rpm with a 727. A LOT of rpm.

Well, I havent reached that yet but I'm open to more info/insight. I'm thinking a 5 speed to pair with the 392.

 

[RenVill]

There are 3 center sections.



741 (weakest, least gear ratio options)

742 ( middle of the road for strength, wide range of gear ratios)

489 (strongest, widest range of gears available)


Cass at doctordiff.com can set you up with what you need.

You can put an ad here, you can look on EBay, Craig's list, Facebook market place

Are either one of these what I need? Will it complete everything I need to have installed?

Mopar 8 3/4" (8.75) 489 Case Third Member
or

Mopar 8 3/4" (8.75) Nodular Iron 489 Casting

New, Mopar 8 3/4" nodular iron 489 casting includes forged steel caps and billet steel adjusters.

www.doctordiff.com

 

[RenVill]

Mopar 8 3/4 Suregrip 3rd members - auto parts - by owner - vehicle automotive sale - craigslist

Mopar 8.75 third members available;

2.76 to 4.56 ratios available, open, spooled, Suregrip, or Suretrac, have 10 Suregrip third members rebuilt and ready to go, have all ratios, or can build one to your specs. Prices range from $350 [used open] to $1450 [all new parts] and many in-between. Over 40 years experience building Mopar and Dana axles.
2.76, 2.94, 3.23, 3.55, 3.73, 3.91, 4.10, 4.30, 4.56

I’ve met this guy before and he’s just an old school Mopar gear and axle guy. He works at his home shop and has retired to Lake Havasu. He is near the AZ/CA border on I-40. He ships too.

(909)725-7211, I forgot his name.

Thanks I'll reach out with some questions.

 

[33IMP]

Assuming an overdrive 5 or 6 speed stick, I would recommend a clutch suregrip, with 3.73 or 3.91 gears, in a 489 case.
It will accelerate great with your 360/727, but probably have more rpm on the highway than you will like.
The $1320 center section will be what you need, the other is just an empty case. I would call Dr Diff about your needs. He's a good guy, and LOTS of members here recommend him.

 

[Dartwizer]

Yep,Dr.Diff.
Very knowledgeable and helpful .

 

[str12-340]

What do you plan to do with the car? Are you driving it much? Are you drag racing it, road racing it? if racing, how much - a couple times a year for fun or is it what you are primarily building the car for? Any of the 3 chunks might be fine or you might need a special build for strength...

 

[RustyRatRod]

I recommend a Ford 9".

 

[RenVill]

What do you plan to do with the car? Are you driving it much? Are you drag racing it, road racing it? if racing, how much - a couple times a year for fun or is it what you are primarily building the car for? Any of the 3 chunks might be fine or you might need a special build for strength...

90% street and highway driving, 10% any kind of hard driving like drag, etc. Nothing serious.

 

[str12-340]

IMHO you could use any of the three casings with a Sure Grip and the right gears with your 360/727. If you do any real highway miles then I would suggest 3.23 gears. Once you get into the Hemi and OD 6(?) speed you will probably want to get another chunk to take best advantage of that combo, and selling a 3.23 Sure Grip differential is easy.