Required drivetrain mods for 4" lift?

Required drivetrain mods for 4" lift?


Lake Charles, LA
1982 Laredo CJ7
Dana 300 Transfer
Dana 30 fr
Model 20 rr
4.10 gears
I have gotten mixed opinions from fellow jeepers locally about what kind of modifications are required when you do a 4" lift on your jeep. They never gave me solid answers, maybe you guys can help me. I have 4" procomp lift springs and a drop pitman arm. My questions are.....does this kinda lift require new custom driveshafts and what degree shims should I use f/r? Thanks in advance ya'll have always been extremely helpful.
I had a 4 inch Pro-comp lift kit on my 85 CJ and the front drive shaft needed to be 1 1/2 inches longer. I also had to convert the rear to a double cardan (CV) style because unless I wanted to drop the belly pan with spacers, I was having horrible vibrations from it. The CV style rear drive shaft needs a companion yolk which will replace the yolk you have on the Dana 300 rear output now. This CV drive shaft will allow you to keep your belly pan flush with the frame instead of losing valuable ground clearance where you need it most by dropping the pan to lessen drive shaft angles. Contradictory to why we put a lift on the Jeep to begin with, for more ground clearance not to turn around and take it away with spacers right? Angle your rear axle pinion up to point straight at the yolk on that Dana 300 and there won't be any vibrations. The front does not need to be a double cardan because it is substantially longer and only rotates when you lock the hubs in 4WD, usually at much slower speeds. As far as shims, try to get steel shims if you must use them because the aluminum ones crack and will fall out on the trail. I didn't use any shims in the front because again, the drive shaft doesn't turn as fast as 4WD is usually slower speed. Shims up front will also negatively impact your caster angle possibly causing wandering, drifting and poor handling if the shims reduce your caster by too much so be careful. The rear will need whatever shim it takes to point the pinion correctly at the rear transfer case yolk, whatever that might be because you'll have to just do it and find out. Worst case scenario to do it right, you could cut and move your perches on the axle housing once the angle has been figured out then there will be no shims used.

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I have gotten mixed opinions from fellow jeepers locally about what kind of modifications are required when you do a 4" lift on your jeep. They never gave me solid answers, maybe you guys can help me.

And now you see why. It seems some people get away with it and some don't.
Really that's not a big enough of a lift to worry about other things. Your drives shafts should be fine. 6" lift you need to start worrying about more things. Good luck.
I got my first CJ5 and it had a 4in ProComp lift and drove like poopie.I had to add 4deg shim to the front,drop pitman arm and lots of tweeks.Trans case was dropped 2in.
This and a good alignment made things work decent
So I am assuming the "ones" that get away with little to no mods either lucked out or is it the type of terrain they wheel on? I would figure that extreme articulation would definitely seperate a stock driveshaft before mild trail riding would, right? Hardcore wheeling isn't exactly in the near future yet, I wanna make sure my cj is setup well before I hit the hard trails. Thats why I keep hitting on the driveshafts? I am torn should I play it safe, wait and lift later after I got the driveshafts. Or say screw it lift the cj and see how it goes?

I believe your right, the way it's wheeled and also how stiff the springs are
all add up to what will work and what doesn't.
If I were you I'd do the lift and see If I needed new shafts, you might be one of the people that gets away with it.
Sounds good I will do it on my next few days off and post an update let ya'll know how it went. But as far as the shims for the AMC20 , I will shoot for is the steel 6 degree first if that don't work then go to the 4 degree shim sound reasonable? Anybody want to hit on the shims once more?
I'm not sure what my rear is, they came with my superlift springs.
I don't have any in the front.
Any suggestions on where to find the steel shims? Everywhere I have looked so far has had only aluminum lol. :wtf:
Morris has them for a very reasonable price
my 2.5" procomp lift came with shims. i dont run any in the front and the rear where 2.5 degrees but i have a smaller lift so yours will be different.

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