Pinion angle

SHort driveshafts do not take to lifts well. You want the angles to be equal oposites of one another so they cancle out at reasonable drive angles. If they are not equal, vibration can set it.

CV's is the best bet here. YOU DO NOT want to raise pinion on front pig with shims and this will throw off caster angle on front axle and can create serious stabilty issues (Death Wooble for one). The only proper way to raise pinion on front axle is to cut and reweld tubes.

----------------- TheSnoMan.com

Thanks. My apologies for not explaining fully. I need to clarify that my question refers to the rear axle only, the front one will be OK. Also, mainly I'm trying to decide at what angle to weld on the spring perches.

Option 1 is to attach the perches so that the pinion angle is parallel to the floor, just like stock. Once the lift is in, the angles would be reduced by using a SYE and a single cardan DS would be used, keeping TC output and axle pinion parallel.

Option 2 is to attach the perches so that the pinion is rotated up a few degrees if installed without shims and perhaps shim it down to parallel until I get the 2.5 inch lift, at which point it would be shimmed to point up to the output of the TC and a CV driveshaft would be used along with a SYE.

SOmething to remember here that many overlook when setting angle. While you are on the right track here setting equal oppsite angle (which I assume you are trying to say with your parrallel term) you want to set the rear pinion a few extra degres down. The reason for this is that under load, the torque on wheels caused axle housing to wrap up a bit in springs changing the angle. This is a normal reaction and the amout od wrapup depends on tirres size and spring stiffness but it does occur.

You have four options here, The first is to use regular Ujoints at eithe end with yoke phased 90 degrees apart and have equal opposit angle as stated above. The second one is to align the driveshaft parallel to Tcase outputshaft (which may not be practical) and use a CV on rear axle pinion flange. The third is to align the static drive shaft angle with perch welding or shims (with a few extra degrees of down tilt for torque reaction) and install a CV on Tcase output yoke. (this is more viable) and the forth choice is to use CV's on both ends of drive shaft and set rear axle pinion up some for clearance but not too far top compromise oiling of pinion bearings. When you doe raise pinion up a lot (say more than 10 degrees or so from level) you want to increase the lube level in rear axle a bit so that pinion bearing are properly lubed and cooled as all times. Off all four, the last will be the most relaible with first least reliable because even if you get angles right to cancel out velocity variations that cause vibration as Ujoint flex, the torque capacity of the joint decrease as angle increases and it will wear a lot out sooner. The second and third choice would have a lot better joint life and the forth the longest. I hope I did not muddy the water too much for you.

----------------- TheSnoMan.com

Not muddy, makes sense. Thanks for the ideas. One other question: How bad is it to weld and reweld on axle tubes? Here we are talking about removing the factory-attached perches (first welding), welding perches in a position suitable for the pre-lift installation (second welding), removing these perches at a later time, and welding perches in a new position suitable for the lifted jeep (third welding). That is a lot of welding, will it harm the tubes, make them brittle?

Thanks

The problem with welding is that if not done properlly, it will bend the axle tubes. Every time you make a weld on the axle tube, after the weld cools off, it will curve slightlly the tube towards the weld. The welds must be performed very carefully with the minimal amount of welding needed. Make small welds at a time, and wait for the axle tube to cool before welding on the next spot. Don't use water or anything else to help cooling. Do not get carried away with the welder, don't make continuous passes and avoid welds with deep penetration. Study how the factory-attached perches were welded and try to reproduce the same weld pterern. If you follow the above, I wouldn't be worried about the axle getting weaker.

As far as what setup with the drive-shafts to use, it all depends to how much lift you plan to install in the future.

2.5" lift is about as much as you can get away without a SYE, but it would require both pinion angle adjustment and a bit of TC lowering.

However if you have the SYE installed in the TC, and since you will need a new drive-shaft for it anyway, why not get one with a CV? It would be a much better combination than no CV at all. And with 2.5" lift you wont have any complications. IMO it would be more practical to weld the perches once as close to the correct position for a 2.5" lift and shim it lower until you install the lift.

Bill Spiliotopoulos, '96XJ, '06 TJ.

This is good advise. You are more likely to overheat tube cutting perches off if not done correctly. You want a very hot flame with plenty of oxygen flow when you "cut" with a torch and get job done as quickly as possible. I would cut parallel to tubes with torch and get perchs off and firgure on replacing perches so that you do not have to heat tube much cutting them off. Grind tube after it cools if you need a better contact surface before rewelding them on.

Agreed

Not a bad idea on the shiming until lift is installed but if he goes with a double CV set up (CV's on both ends of driveshaft) it will not be a issue at all.

----------------- TheSnoMan.com

With a SYE and CV shaft, pinion should be pointed at the T-case output minus

1-2 degrees to account for axle wrap. The lower u-joint should be nearly straight, with all the angle taken up by the CV part of the new driveshaft.

HTH

Carl

I am not aware if it is possible to have a double CV rear driveshaft for a Wrangler. The driveshaft is so short that there might not be enough length to accommodate the slip joint and CVs at both ends. Also I haven't seen one provided off-the-self, so it would require ordering and buiding to specifications, which would probably be more expensive than using the common way of a single CV shaft. It wouldn't justify the extra engineering just for a 2.5" lift.

Bill Spiliotopoulos, '96XJ, '06 TJ.

Wouldnt a CV on each end cause the shaft to flop up and down? I cant imagine

4 joints on a single driveshaft...

Carl

I don't believe it is possible to have one with dual cardan CV joints. But you can with ball CV joints, like the ones used on the 2007 wrangler rear driveshaft (and it is a weaker design that cardan joints). Anyway, it is an overkill to have a dual CV driveshaft.

Bill Spiliotopoulos, '96XJ, '06 TJ.

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God Bless America, Bill O|||||||Omailto: snipped-for-privacy@aol.com

When ever I need a speacail drive shaft, I have it built at a local drive shaft shop. I do not depend on online prefabbed ones. Even if I wind up paying a few extra bucks, I also wind up getting EXACTALLY what I want, not the closest fitting off shelve unit. Because of this I never really looked at what is availble ready made so I cannot comment on ready made over the counter solutions.

----------------- TheSnoMan.com

No more than he front drive axles on a front wheel drive car of truck with IFS. As far as strength, axle shafts handle more torque than any drive shaft. It is quite feasable and doable with correct design and parts.

----------------- TheSnoMan.com

Thanks to all who replied, I have a beter perspective on this now. Thanks for the welding advise Bill S.. Although I will have a good welder do it, I'll make sure they take this into account.

Did some angle measuring last night and found out the the stock pinion angle is up 2 degrees and the TC output is down 2 degrees. The operating angle of the stock DS is right at 10 degrees (12 degrees from the floor). Also, based on trig calculations assuming a super short SYE will be used, the plan is to:

1) weld the perches so that the pinion points up 8 degrees from parallel to the floor 2) shim down with a 6 degree shim untill the lift is installed 3) once lift is installed, shim the opposite way to get the required angle, looks like it should require less than 6 degrees even in the worst case 4) use a regular CV style DS (one u-joint at axle pinion and double u- joint at TC)

Does this sound reasonable? No issues with 6 degree shimming?

Just remember that you want the static angle on pinion a few degrees more in opposit direction than one on Tcase because the axle will wrapup and reduce the angle on the pinion from axle torque with a leaf spring suspension. Sometimes several degrees. THis is why some get vibration at certain loads and speeds and cannot figure out why.

----------------- TheSnoMan.com

Thanks to all who replied. I will most likely go with the plan described.

Sno,

Thanks for citing examples, I stand corrected.

Carl