Vibration in the rear after axle swap

If it spun smooth before the lift and goes away when the shaft is pulled I am pretty confident that's a u joint angle issue.

Just to add, even if you get the pinion perfectly level with the T case output, if the operating angle of each u joint exceeds the limits, it will vibrate.
 
You know I was wondering that. It has balancing weights on it, but I have a different rear axle, so it can't be balanced to the rear end. I've always wondered about everyone saying to mark the DS to the yokes so you can put it back exact. What do you do when you have changed the yoke, (and the whole axle). Are there shops that balance them again with the new components in the vehicle? If you put a new SYE in, you are even going to change the front yoke and shaft also. So both have changed. I do wonder about that. Also, the PO put the MML on when he didn't have any suspension lift, just 1.5 body lift. He mentioned something about shifters when I bought it, but it was a kid and in talking to him he dad had done the work a year or two before. So he really didn't know much. I think the MML was put on to help shifter linkage, but that is a stretch for me. But it was bone stock and the back springs were sagging about 1/2 inch.
 
Just saw your last post. When I get the arms and get the DS off, I will post angles measure on the rear end and TC. I haven't gotten out to get the gauge yet.
 
I would say the main reason the BL and MML were done together was so the PO didn't have to mess with the fan shroud.
 
BTW, anyone that gets to AZ, please drop me a line, I’ll do anything I can to help! Second only to Moab in trails IMHO. Especially with the diversity of desert to mountains and so much public land.
 
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JLANEF said:
First I want to thank everyone so much and I am taking all comments to heart. That's why I posted. Taking them to heart is also why I want to challenge us all one last time before I put $1000 in arms and SYE. I know I am an older guy and stubborn, but I know at least half dozen jeeps here in Phoenix with 2.5 inch lift, (and my son's 2001 I helped him install), with stock everything in the back suspension and driveshaft. None have any vibration, let alone the level I have. I put on a 2.5 inch lift and a new axle and I have a nasty vibration. Everyone is quickly suggesting it's pinion angle and SYE and adjustable arms etc are needed. Plus this forum has helped me find out I have motor lift, which should make the angle even better than stock. So why am I the only one I know with a 2.5 inch lift that needs all this. I appreciate everyone's help and this forum has saved me so much and helped me so much in the 1.5 years I have had the jeep. Just frustrated and trying to make sure before I spend that kind of money. Everyone, please do not take offense, I'm just asking and appreciate all the help very much. I was an engineer before retiring so I have to ask. Personality quirk!!
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Reading your first post you stated that you had swapped out 1 7/8" spring spacers and rancho 5000 shocks for
a set of rancho 9000's and 2.5" rancho springs, correct.
Now you say you know other people that run a 2.5" lift with no vibration problem correct.
If you take a look at several lift manufacturers websites you will see most of them include transfer case drop hardware with their kits. They do this for a reason, to help prevent driveline vibrations. Looking at your pictures it appears you do not have this installed.
Now it you want to prove yourself correct before investing another 1000.00 in components. I would suggest heading over to your local hardware store and purchasing a box of 1/2" washers along some longer 1/2 x13 bolts.
You can stack 6-8 washers between the skid and the frame to drop it down about 1/2-3/4 of an inch then go drive it and see if the vibes go away.
I know several people that have run into the same problem. one of them installed a 2" budget boost kit and had vibes, one had a 2.5 quadratec lift and the other a 3" zone lift.
Each of them addressed the issue in a manner which best suited their situation. two of them installed a t/case drop kit because their vehicles don't see offroad.
The other guy, I installed a SYE kit and CV driveshaft along with a set of adjustable arms.

https://4xshaft.com/blogs/general-tech-info-articles/tail-shaft-conversion-kits
https://4xshaft.com/blogs/general-tech-info-articles/slopes-vs-angles
 
Thank you. Excellent advice. Will try and find time this afternoon to try that! I’m also glad to hear other people have seen this problem with ~2.5 inch lifts.
 
One question for anyone. if I drop the TC 3/4 inch will the vibration probably prevail because my pinion angle appears to high? I understood from many posts that if the pinion angle is too high the only way to fix it is with an SYE and or control arms.
 
Vinman. No worries, really long post! Picked up adjustable rear lower and upper and trackbar today. Getting bolts to test lowering TC this afternoon. Picking up angle gauge tomorrow, then a really busy day! If I lower TC 1/2 inch, will anything change materially or negatively with shifting linkage or front of engine moving, I.e., fan getting into shroud or any hoses?
 
JLANEF said:
Vinman. No worries, really long post! Picked up adjustable rear lower and upper and trackbar today. Getting bolts to test lowering TC this afternoon. Picking up angle gauge tomorrow, then a really busy day! If I lower TC 1/2 inch, will anything change materially or negatively with shifting linkage or front of engine moving, I.e., fan getting into shroud or any hoses?
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I would say no, it should not....but with the Motor Mount lift the fan shroud could.
With the MML , 1/2” to 3/4” spacer for TC skid to drop it, and adjusting the rear pinion is a definite “should”. I’ve learned some are stubborn, but it should fix what you are experiencing.
It’s possible just fixing that pinion angle to match, but might unless you’re big time concerned about clearance wheeling, 1/2” to 3/4” less clearance won’t be an issue.
 
Well the HF next to me was out of angle gauges, so poor start to the day. Then I went to the hardware store and bought bolts and a box of washers. I lowered the center skid plate down ~3/4 inch. Took it for a test drive. The vibration is still there, but is muted at least 50% and probably 80%. At 65 is is certainly 75% down and I can only feel the vibration and hear the "growl", (which now is more of a drone going up and down and still not sure I am hearing it, may be the vibration). Only time it is 50% of what it was is up at 75 mph. So I am proclaiming first level victory and congrats and thanks to everyone who stuck with drive line angles. And special thanks to William in NJ that suggested the bolt and washer TC drop to test the theory! Now for more questions. Is more always better on TC drop. Is it possible 1/2 inch gives less vibration? I don't think I want to go over 3/4 of and inch, just never heard of over 3/4. On the pinion angle I will work on that later this week when I get my angle gauge and have time to tear into Control Arms. May not even get to it this week. But I have a lot of hope that with the TC drop, (which I will need to get a kit and do right), and pinion adjustment, I will get rid of all the vibrations. Hopefully maybe even be able to raise the TC back up since we are now pretty sure it is drive line angles. But if I can't, I can't. Maybe down the road I can do the SYE and take the TC back up. But my trail activities for the next year are not going to test my losing 3/4 inch clearance in the center skid plate. Thanks again everyone, any more comments greatly appreciated, but I probably won't update until next week. I just don't see getting to control arms until then. Plus that may be a day or two anyway with experimentation. TXS
 
My skid is dropped a full inch, no problems.

But you're right, it could be you need less drop as well, just have to play around with it.
 
Thanks W! I was unsure it more was always better or not. Sounds like it is just like the rear pinion angle. May take some experimenting to find the sweet spot.
 
You can experiment with how far you drop your skid. They sell drop kits for tj's that go up to a 1" drop.
I just wouldn't waste your money on it. Buy longer bolts if you have to and add more washers. Just make sure you check your cooling fan clearance, you don't want to hit the shroud.
That drone/growl that you are hearing may possibly be your driveshaft binding due to the angle being out.
I know you said you put an axle in your jeep also, did you make sure to change the diff fluid? or at least make sure it was full.
Once you install adjustable rear arms and a SYE you will be able to do away with the dropped skid and dial your pinion angle properly.
You can check with JB Conversions, he sells a SSYE kit that is really nice and then order a new rear DS from Tom Woods.
Good Luck with everything.
 
I was paying attention to the fan and shroud. All good there. I should have pulled the cover on the diff, but didn't. I did check the lub coming out the inspection hole. Was full and looked good. Trusted the guy on the gears!
 
JLANEF said:
Thanks guys! Is there any disadvantage to transfer case drop other than clearance? Any problems with shifter linkage?
Click to expand...
yes there is.. i can't put my yeti or a bottle of water in my front cup holder and shift to second (manual trans).. its annoying! its coming out verrrry soon!
 
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