Measured my driveline angles w/ 4 in. lift

[brielly]

Thought I'd post this since it pertains to many of us with lifted trucks..... After installing the BJ's 4 in. lift I noticed a bad vibration when acelerating almost like a thumping feeling when really getting on the gas. I had read some posts about removing the wedges from the springs but before that I had the driveshaft balanced and new u-joints installed. Unfortunately that didn't cure the problem. Measuring with the wedges I found that the angles on the t-case and pinion were not equal/ opposite like they should be. Instead the pinion was pointing straight at the t-case which is ok for a cv style shaft but not for a stock cherokee. I just removed the wedges yesterday and the vibration is gone. Measuring the angles without the wedges I found the u-joints are operating at 12 degrees which is a bit much but at least the angles are even now and the vibration is gone. I'll have to see how long my u-joints last at that angle but I figure they should fair better this way. I'm interested in hearing from others who have experienced similar problems and what worked to fix it.

[Tad]

Never measured my rear angle back when I ran a D44 but went 4 years with no shims at 4.5" of lift. When I swapped to the 14-Bolt this summer they looked just like new.

[89grand]

I took my rear spring wedges out too. I haven't had a problem in roughly 2 years or so. I'd change the u-joints too, since you've changed their operating angle quite a bit.

[68wagoneer]

When I did the prototype BJ's 4" all spring lift on the '68 Wag
I wound up pulling the wedges too. Also had to buy a new conventional 2 joint driveshaft. It had a ball and trunnion type POC. Basically if you run a conventional shaft you want the t-case output shaft angle and the rear diff input shaft angle to be the same or at least within 1 degree. Anymore than that and you can count on bad vibes and in need of a u -joint slush fund. You can consider the t-case angle to pretty much be fixed without major work... The diff angle is easily changed (to a degree!) with the magical and troublesome wedges. With a double cardan or cv shaft you can get away with a whole lot more but unless you have over 6" lift or are doing some major wheeling OR just can't get the angles right save yo money. Pirate 4X4 has a ton of good stuff on this, but then ya'll probably up on it anyways.
Mike

[mcstord]

that is awsome I put a 4" Bj lift on a while back and I noticed a new sound. I'll have to take the wedges out and give her a try

[HotRodYJ]

Most consider 10 degrees to be the max normal operating angle for a U-joint for dependability. I'm curious, with 12 degrees at normal ride hieght, do the yokes bind when you flex it out? One trick to lower that 12 degree working angle on your joints ..you can drop the t-case a bit which will then allow you to turn the pinion up a little as well to match the new t-case angle. Even on my baby Jeep and it's short little d-shaft and 5" worth of suspenion (SOA) I was able to get my rear d-shaft down to 5 degree working angle on the joints by dropping the t-case just a little. That allowed me to save the cost of a SYE for a couple of years.

[Serious Johnson]

Though I've not measured, rear driveline angles on my Wag appear to be at least 10 degrees -- probably a fair bit more with my ultra-long T-18a/208 setup. My +_4" lift was via junkyard BDS springs off a Chreokee, and I reversed the supplied aluminum shims to point the axle pinion down, which resulted in dang near perfectly equal & opposite angles at rest. The ol' Wag runs smooth as silk, but I haven't got standard u-joints to live more than about 15,000 road miles. Once when I towed a pretty big load (maybe a thousand pounds of tongue weight) without a W/D hitch, I noted some vibration back there, but can't say for certain whether it was due to unequal angles or already fairly loose joints.

S.J.

[babywag]

Yep, had to remove mine too....massive vibes and angle was way off.

No issues w/o them.