Rear end swap

[64dartgt]

Pulling an 8.25 out of my 73 Charger and replacing it with an 8.75 from another 3rd gen Charger...will I have to alter the drive shaft length?  Change the yoke?  Thanks in advance.

[doctor4766]

I didn't need to do either of those in my '69.
Not sure that a '73 would be any different if the diff swap is all you're doing.
Now if you were changing out a small block/904 combo to a BB/727 combo at the same time that would be a different matter right...

[RallyeMike]

If the rear drive shaft U-joint is the same size as your axle, its a bolt in. If not the same size, then buying a conversion U-joint which will match up small to big is the fastest, cheapest way to make it fit.

Mike

[Kern Dog]

The yoke on an 8 3/4 sits forward about 1/2"  compared to an 8 1/4 axle. Many stock driveshafts that I have seen sit one inch to 1 1/2 inches out of the trans.  That doesn't leave a lot of wiggle room, but it may be okay. You could check to see if this matches the layout on your car with the existing axle. to modify the driveshaft, a cut, balance and new U joints usually costs around $100 here in Sacramento.

[64dartgt]

Thanks everyone.  So possibly a bolt in, but may have to change the U-joint.  If the yokes differ a conversion U-joint is available.  There is a driveshaft / differential place nearby.  I'll probably have them take a look at the used 8.75 and perhaps change out the gears.

[64dartgt]

Picked up the 8.75 today.  Bonus - it's got a 489 center section.   

Seems like all I have to do is remove the brake drums and the five bolts on each side to pull the axles, then just the ten bolts on the center section and it will come right out?  I want to know if it is truly a sure grip and understand that the ratio may be stamped on the ring gear.  The previous owner was told it was a 4.11 sure grip.  All he knew was that spinning one hub spun the other in the same direction.

[Kern Dog]

There never was a 4.11 but there was an  4.10 available.
The axle shafts  need to be unbolted and pulled out  less than a foot. The center section can be pulled out after the 10 bolts are removed. YES, the ratio should be cast into the ring gear. Chrysler also cast DATE codes in the ring gear, so you will know if the gears are factory or not. The '489 cases were phased into production in mid 1969 and ran to the end in 1974. Any factory installed Sure Grip in a '489 case would be the Auburn cone type. They are identified by the smooth case with small rounded "windows". These are good units, but once they are worn, they cannot be rebuilt without a few drawbacks. If you can find a "Spicer" type SG unit, grab it because it IS rebuildable and can be swapped into the '489 case.

[64dartgt]

Thanks.  Is it easy enough to check this unit out at home in terms of the bearings and ring and pinon or should I just take it to a pro and have them scope it out?  If I want to change the ratio, think it is cost effective to do so, or should I just ditch the auburn unit rather than sink money into it, if it is Auburn.