Driveline Experts

Ok, I installed a skyjacker 2-1/2" lift, greaseable shackles that are probably 1" longer than stock. Immediately, (from the first test drive), there is a slight metal to metal sound. Almost sounds like a brake hanging up but it is not. I have no vibration through 65mph anyway, but it does wander some. I bought a angle finder to measure my driveshaft angles. The front shaft is at 13* both ends, the rear is at 21* both ends. Does anyone know what the acceptable measurements are for a cj5?
Thanks

 

Could your driveshaft splines be fully extended? You can put Jeep axles on jackstands to check for that & yoke rub under full rotation.
Where are you Upstate? I have family all over Clinton County.

gj

 

Southerntier of NY, between Jamestown and Binghamton. I did lift the rear end, put in gear and let it spin at idle. Didn't hear anything then.

 

I've riden through Binghamton a few times, used to camp in Cobbleskill once/year.

What about your manual & visual inspection of the driveshafts, u-joints, etc?


gj

 

There are some good tech articles on the Tom Wood's site: http://www.4xshaft.com/

Most drive shafts will, depending on components used, incur a binding interference at about 30 degrees. You DO NOT , I repeat DO NOT want to run a drive shaft at any where near this angle. you need to allow for axle droop, frame flexing and differential roll. All of which can momentarily alter the operating angle of the "U " joint to the point that it will cause what I refer to as an IMMEDIATE & CATASTROPHIC FAILURE. Ultimately you need to be certain that your driveline will rotate freely under full axle droop.

21 degrees sounds like a lot. Rated maximum is about 7 degrees according to the above article (Driveline Geometry 101).

 

What's the best way to fix it?

 

From what I've read, there are shims available. The disadvantage with shims is that the pinion will not sling oil properly to the pinion bearing & seals at crawling speeds if you change the pinion angle too much. I think that some 4"+ lift kits (such as spring overs) switch to CV joints on the rear driveshafts.
I took the easy way. I made 4 3/4" long reinforced shackles, single military wrapped the HD springs, added 2" over Rancho shocks & used a 4" bronco body lift kit. I had to shorten my driveshafts to fit the D44 front & D60 rear cases & cut a corner from my oil pan skid plate & dimple the corresponding corner. My prop caught the skidplate & tore it out on Jeep's maiden radical hill climb. I made it off the hill & back to civilization with 6 body screws in the oil pan holes & 3/4 quart of oil. All that I had to do was add some length to my steering shaft and I can run my 33X12.5X15' Mud brutes with rub only under moderate to severe flex.

gj

 

You can deal with the high pinion by overfilling the gear oil, then adding some ATF to prevent foaming. I think I read this on the Tom Wood's site, or maybe at Randy's Ring & Pinion. As shown on the Tom Wood's site, you can use a CV on the TC end and tip the housing up to be in a straight line with the driveshaft.

 

The ATF will help to swell the rubber seals and will likely even provide some protection to the pinion bearings once the warm ATF/lube mix coats the bearings and leave a residue.

gj