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Old June 19th, 2018, 11:02
LLLux31 LLLux31 is offline
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Join Date: Oct 2017
Location: NJ
Posts: 76
Re: 1979 f150 Axle swap

Old thread but wanted to add some 9" info.


To swap in a 9" you will need to cut off the stock perches/mounts. I used a couple Diablo 1mm cutoff discs and a grinding disk on a 4.5" grinder. Then used a 60 grit flap disk to smooth everything down and clean up the tubes.


I then put the 9" under the XJ and used my jack handle with an angle finder to find the correct pinion angle needed. This was ~20 so I set the pinion angle at 18 degrees according to various driveshaft manufacturers wanting it ~2 degrees under. XJ leaf spring perches are 44" apart center to center



My 9" is 65" wms to wms so I measured in 9.25", set the perches on the tube with the angle finder on them at 0 degrees (pinion tilted up 18 degrees from horizontal). Then tacked them on.


My XJ at my buddies garage and my welder is at my house so I will bring the axle back and test fit it. If I need to adjust it's very easy to knock the perches off and reposition them before fully welding it.


Once it's test fit I will then cut out some 1/4" thick shock tabs.
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