what center section should a 1973 340 Cuda have?

[scf100]

and if I want to swap to a 3.55 suregrip what all do I need to change out?

Thanks!

[Chryco Psycho]

489 case is typical , you can swap gears in your case or just get a new complete case with gears & sure grip .
I would contact Dr Diff in MT either way

[RUNCHARGER]

I second what CP says. Also, always check the casting # (it is on the lower drivers side of the diff casting), these cars are pretty old and you don't know what parts may have been changed over the years.

[anlauto]

Regardless of what center section you currently have in the car, you would need to buy a new 3:55 ring & pinion, a bearing kit and a new sure grip unit if the car doesn't have one. These parts are available for any center section, so first start by identifying what you have, then I also recommend calling Dr. Diff

[nsmall]

Let us know if you need help identifying what you have in there. 

[scf100]

thanks guys.....was told its an open rear so eventually want a 3.55 suregrip

[HP2]

Well, I'd say put both rear tires in the air and check tire rotation to confirm/deny if you have an open diff. Then knowing that, you can then drop one tire to the ground to figure out what ratio you currently have. Finally, you can look at the casting number on the outside of the case to determine which case you have, which will be necessary to know before pursuing any parts, replacement pieces, or upgrades.

[73_Cuda_4_Me]

My 73 has a 489 center section, 3.23 ratio. I added a locker several years back... rebuilt carrier bearings and pinion bearings last spring.

Further to HP2's check - raise rear wheels off ground, spin one wheel... if other wheel spins opposite direction, it's open. If it spins same direction, it has a sure-grip of some sort.

Since you have to pull the axles, be ready for 'mission creep'... may need new axle seals, 'possibly' axle bearings, inner/outer axle tube gaskets, etc... brakes may come into play as well, once you get in there...

You may get lucky and not have a lot to replace, but better to be aware going into it...