School me on pinion angles for 4-5" shackle flip

[Lotsa_Faith]

I did some searching around just now on pinion angles, and have come up with two different 'rules of thumb' just wanna get some opinions on which I should go with. Currently I have a cucv 14 bolt rear that I'm getting ready to install, and I'm thinking it will be easier and stronger to set the spring perches on it at the degree I need rather than stuffing a shim between my springs and zero-rate, that'd just be one more thing to pop out one day. I don't have my truck with me right nwo to measure, but here are the specs on the rear suspension:

-stock 3/4 ton M1009 springs
-homebrew shackle flip like this: http://coloradok5.com/shackleflip.shtml

Now, from searching I've found that you want the angle of your driveshaft/output shaft to be almost exactly the same as the driveshaft/pinion for the optimum angle if you're running a regular driveshaft like I will be (slipyoke out of a 208). If running a CV driveshaft, you want your pinion to be pointing right at the output shaft of the tcase. However, I read a few different people's posts where they ran a regular driveshaft and had the pinion pointing right at the output shaft without any issues at all...what's your opinion? It would be much easier to set the springs in this set up instead of doing all of the angles and measuring the other way.

Also, anybody have the 4" shackle flip set up, and if so, what are your pinion angles set at?

 

[EIB8400]

When I installed my 14bff and shackle flip I cut the and welded the perches so the pinion was point at the output shaft on my 208. I had a bad driveline vibe at about 20 mph (shook the whole truck). I dropped the transfer case 1" and now it works perfect. I don't have any bad vibes up to about 55mph. I haven't gone any faster than that yet.. Making sure nothing falls off before any high speed runs

 

[ezoliver]

The whole idea behind a shackle flip is it rotates your pinion up with the lift. Should put you close really close to what it needs to be without any shims.

 

[4X4HIGH]

What you have read is correct. There is a problem though depending on how much lift you're going to run if this is a blazer (not familiar with military lingo). Standard driveshaft WITHOUT a CV the output shaft of the t-case and the pinion need to be the same angle otherwise it will cause a vibration. The other thing is the working angle needs to be 1/2-3* otherwise it will eat u-joints. A short wheel based vehicle it is nearly impossible to achieve both at the same time so in this case you would be best to make the output and pinion the same angle to avoid the vibes and then keep up on lubing the u-joint regularly.

 

[scrappyk5]

When I installed my 14bff, which came from a 1ton truck I had to cut and install new perches. So I first installed my echo bit flip, put the axle underneath and search for the right angle before I welded. I also made sure the weight of the truck was on the axle to get the perfect sitting stance. I didnt have a degree finder so I "eyeballed " it at the pinion and set where the pinion was angled downward about a hair or two. I do not have any vibs till I get up to about 70mph, which I think has alot to do with the 37" military tires.

 

[Lotsa_Faith]

Thanks for the info fellas, I was hoping to get the perches set and the axle painted and ready to throw in as soon as the truck gets here next weekend, but I'm gonna wait until I do some measuring on it and get the angle of both sides of the shaft about even!

 

[63chevyll]

ill speak for myself, but i normaly cut off the perches and then add new ones.

Its alot easier and less time than saving the old ones.

 

[scrappyk5]

ill speak for myself, but i normaly cut off the perches and then add new ones.

Its alot easier and less time than saving the old ones.

I second that. Thats how I did mine, cut off the old installed the new.