8 3/4 rear sure grip with 323 ratio what`s it worth?

[Barracudadan]

I have the original /6 rear end in my cuda with a 318 and an automatic trans right now. I am upgrading the engine to a 360 with a mild cam in it. I may be able to get this rear end I mentioned in title of my post from a 72 cuda same as mine, but would like to know what is a fair price for it.

Also does anyone know what the ratio would be right now in my stock /6 rear end when I am cruising down the highway it just doesnt feel right it works fine just doesn`t "feel" right is the best way I can explain it. I would like something that would give me a nice cruising gear for the highway but yet still have some get up and go from a red light.

[Gumby]

You will probably have to change axle shafts as well. Splines may be different. Most go for 3.55 or 3.91. You probably won't get full use out of those gears. 360 low compression smog motor won't net you much.

[brads70]

For all around ratio most use either 3:23 or 3:55 depending on rear tire diameter.
As for your original /6 gear ratio...? I have no idea? Jack up the rear end while in neutral, count how many times the tire rotates for one rotation of the drive shaft. Use chalk to mark the tire to make it easier to count.
You might need to change the speedometer gear to make it read right again if the ratio is different. Not a big deal, or expencive, 20-30 bucks?

My car was a /6 originaly too . When I swapped in the 8 3/4 I have about $650 into it total with new wheel cylinders. I have 3:55 sure grip 489 case. Goes down the hwy at about 3000rpm's or so at 65 mph.  You will also need a different lenght driveshaft. I scored one for $100 from Kijiji

Use these links to figure things out.
http://vexer.com/automotive-tools/speed-rpm-calculator

This chart is for selecting the correct speedo gear

[Barracudadan]

Thanks for the replys. I was thinking this would just be a farly simple swap of rear ends. I never thought about the driveshaft length. This rear end was from a 340 car that has a 440 in it now I wonder if the driveshaft is still there and if it will work. I have not seen it in person yet.

[brads70]

Thanks for the replys. I was thinking this would just be a farly simple swap of rear ends. I never thought about the driveshaft length. This rear end was from a 340 car that has a 440 in it now I wonder if the driveshaft is still there and if it will work. I have not seen it in person yet.

It depends on what transmission both cars have? A 727 uses a different length driveshaft than a 904.
A 440 can only bolt up to a 727, but a small block could have either a 727 or a 904.

[JayBee]

My 1970 318 originally had the /6 (7 1/4) rearend too and it's ratio was 2.76.

[Barracudadan]

It depends on what transmission both cars have? A 727 uses a different length driveshaft than a 904.
A 440 can only bolt up to a 727, but a small block could have either a 727 or a 904.

I have a 904 will my driveshaft work? Or do I still need to find out what transmission is in parts car?

[ChallengerHK]

Look at the shape of the transmission pan and compare to this:

[Barracudadan]

Well I can get the rear end and a complete power disc brake setup off this car he gave me a price over the phone of $600. I`m thinking this is a decent price.

So the transmission on the parts car should be a 727 and I have a 904 on my car which driveshaft will I need mine or the one off the 727 tranny?

[HP_Cuda]

For $600 bucks grab it, normally the mopar sellers want that just for a posi 3.55 chunk......

Well I can get the rear end and a complete power disc brake setup off this car he gave me a price over the phone of $600. I`m thinking this is a decent price.

So the transmission on the parts car should be a 727 and I have a 904 on my car which driveshaft will I need mine or the one off the 727 tranny?

[brads70]

I have a 904 will my driveshaft work? Or do I still need to find out what transmission is in parts car?

I don't think so? The 7 1/4 rear end is shorter than a 8 3/4 .
Actually I'm sure of it as the driveshaft from the 7 1/4 rear end it still sitting in the garage and it's too long for a 8 3/4 rear end

[Barracudadan]

I don't think so? The 7 1/4 rear end is shorter than a 8 3/4 .
Actually I'm sure of it as the driveshaft from the 7 1/4 rear end it still sitting in the garage and it's too long for a 8 3/4 rear end

   So if I am reading all this info correctly it`s possible that neither driveshaft will fit this swap i`m planning.  Leaving me these options get a 727 tranny and use driveshaft from parts car. or shorten my driveshaft off the 904 tranny to make it fit  . I do appreciate all the help so far when it comes to some of this stuff i`m a total NOOB!

[ChallengerHK]

Another option is get a driveshaft made, if you need a different length. It's actually not too expensive.

[Barracudadan]

Another option is get a driveshaft made, if you need a different length. It's actually not too expensive.

True I could do that as well. I was just thinking too I have Doug`s headers and one of the notes was they will not work with a 727 trans so that option may not work for me unless I want to make more changes,which I don`t want to do. This rear end would be a project for over the winter so I got time to figure it all out.

[TinCuda]

Believe me.   I know how frustrating this can all be.


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