Hello everyone!

Just stumbled across this site and was wondering a few things. I have a 1977 Plymouth Volare, its a 4dr car that was converted to a 4spd by the previous owner. When i bought the car the old 7.25 rear was toast, well i got an 8.25 out of a 79 2dr Aspen and really want to do the swap soon. i was wondering if the shock plates (not sure what they're called) will swap from the 7.25 to the 8.25 diff. The ones on the Aspen had a shock mount broken off of one side so i left them in the yard.

also does anyone know exactly how much to shorten the drive shaft or if one out of a 4dr dippy from the 80's would fit?

Thank you all!
Ryan

Measure the axle tube diameter. I know the 7 1/4" is a 2" and the 8 3/4" is a 3", so the shock plates need to be changed because U bolt holes are wider apart. I want to say the 8 1/4" is also a 3" tube but I can't be sure.

As for the driveshaft... the only sure fire way to get a measurment of how much you need to shorten it is to put it on the car and measure. But, to get a ballpark, there is a chart that shows the distances between axle centerline to u-joint for all the axles. You subtract said measurment for the two axles and you'll have an idea of what you should end up near.

Found the chart...
http://www.moparts.com/Tech/Archive/axle/17.html

You are looking at distance 'c'. Looks like you need to take off 1.6" give or take. Doc gives the procedure for measuring length on the last message of this thread.
http://www.slantsix.org/forum/viewtopic.php?p=21516

I think the lbp 7 1/4 all had bigger (3") axle tubes (and bigger bearings) at the wheel (tapering back to the diff), so the axle should be a straight swap using the existing hardware.
For the driveshaft, if the guy used a F-body style trans (short tailshaft), I'd bet a Dippy shaft would be close, but the wheelbase might be different between F- and M-bodies. If he used a long-tail trans, you're definitely going to have to cut one. Pierre is right on by saying measure it!

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