4" lift and driveshafts

[cubsfan]

I am a little over halfway done with my four incd lift on my 71 and have run into many issues over the last two days. First, every bolt we tried to remove was frozen solid with corosion. That wasn't a surprise but it slowed things up a lot. Also, when I got the front end put together, the front driveshaft appears to be about 1" to short now. I did my homework before I started and don't remember anyone saying I would need longer driveshafts for sure. I can't tell on the rear yet because I just got started on it because of a corroded shackle bolt kept me busy for five hours. I can't extend the front anymore by hand and it is not even close. How much slip should I have in a stock driveshaft? It could be full of crap from over the years. Should I anticipate the back being too short. I will check in tomorrow, this truck has thoroughly kicked my ass over the past two days.

 

[Yukon Jack]

I'd be very surprised if your rear driveshaft is too short. Usually there isn't a problem with a 4" lift and the front driveshaft, but you just never know. When I lifted my 69 K20 4" I had to add a CV joint to mine, and that isn't usually necessary. Course my truck has the Rockwell T221 transfer case so that is different from your NP205.

Seems my 69's front shaft had maybe 2" of extension but that is just a guess. My K5 was missing it's front driveshaft when I got it so I can't tell you how much it could be extended.

How much spline is showing when you have the shaft fully extended?

Assuming you need to have your lengthened, probably wise to go ahead and do new u-joints while it is out. Do you have a CV or just a straight driveshaft? Probably looking at about $110 or so to get new u-joints and lengthened.

 

[gaspass]

I lifted my 72 Blazer 5 inches in front and 6 in. rear and had no problems whatsoever with using stock length driveshafts. I twist it up all the time and have had no limitations at all. I have the 350/TH350 combo. Do you have a 4 speed with 205 t-case? Couldn't tell you why you are having trouble.

 

[bp71k5]

I also installed a 4" TV lift and used the stock front driveshaft. I could tell it was extended a bit more than before the lift. Is it possible you don't have a stock front driveshaft? I assume they were all CV style on 4wd.

 

[cubsfan]

After more research, I have determined it is not extending all the way in the front. This is probably due to 37 years of crud inside of it. I can't pull it out far enough to see splines and it only moves about an inch or so. I will try to clean it out and see what happens. I thought it should fit and was surprised when it didn't. Thanks for the inputs.

 

[vtblazer]

I added some to my front drive shaft when I put in the 4" lift, thought it was to close for comfort to run it stock length.

Should be fine for running the roads but if you wheel it, it's not a question of 'if' it'll pull apart but 'when'.

 

[Greg72]

How are you going to be lifting the rear?

I did an ORD shackle flip, and in fact the rear driveshaft got 3/4" shorter than it was with the 4" lift blocks and tension-style shackle setup.

Another thing you might as well know now....when you lift the rear and put on the larger tires it will become more obvious that the wheel is NOT centered in the wheelwell. This was true even from the factory, but was less noticeable with the smaller tire.

When I swapped in my 14BFF axle, I built the springperches with a 2" offset to move the axle back. That made it just about perfect. A 1.5" offset zerorate can achieve the same effect if you don't have a welder and need to cure some "saggy butt" issues anyway.