I was wondering how tall can i raise suspension on my 85 regular cab without having to lengthen drive shafts.

 

not sure but after 4 or 5 inches you need to upgrade your steering

 

i'm not exactly sure either, but you would have to be pretty freakin high up. there is a slip yoke on both driveshafts so that should compensate for the added lift. if you really want to go sky high then, yeah... you might need to lengthen your driveshafts.

usually, you'd want to worry more about the pinion angles on the driveshaft for most 4wheeling purposes. if those angles get too high it can cause some driveline vibration due to the u-joints being at a higher operating angle. this puts more added stress on the joints and they can break easier, especially when 4wheeling. that can be compensated in the rear (not sure about the front, on IFS trucks you don't have to worry about it) by using shims that go under the leaf spring. some lift springs even come with shims built in. i know trailmaster offers some leaf springs like that.

anyway, good luck to ya. peace out.

 

At 3.5" I had no problems until I moved the front axle forward. The slip yoke on the front shaft is not terribly long and you usually have to get that re-worked for more travel if you have flexy springs. Modifying driveshafts is no big deal, measure the length you need and take it to a driveshaft shop. Runs about $100/shaft and takes a day for them to do the work.

 

with a 4inch lift from pro comp or something like that, bolt on without moving the axle forward. you will be fine. anything more and the front driveshaft will have to be extended. the rear can handle up to 6 inch