Rear Drive line rumble...Axle Shims? (1 Viewer)

[kfa670]

I have a rumble in my rear drive line on my 62 after putting a 4-5 inch Mohave lift on. Its pretty bad at about 25 mph under load. Let off and it disappears. At high speeds, 55+ its almost none existent but still there.
I have had the driveline balanced and have it in phase so basically I was wondering if anyone with a similar height lift as shimmed the rear axle. I know Bandicoot did on his mohave system build, but I think he moved his rear axle back like an inch or something too. I believe his were 5* shims. With the vehicles weight on the springs, Currently my rear drive line only has about an inch or 1.5 inches before it bottoms out, I was wondering if maybe this is too little? Could over greasing the slip cause a vibe? Just gave it 2 squirts or so. I asked the driveline guy when I had it balanced and showed him how much clearance he had and said it wasnt' a big deal. Lookin for some input thanks!

 

[lovetoski]

u-joints ok?

 

[kfa670]

U joints are good, checked them when the drive line was out

 

[too tall]

If you let off and it goes away you need to drop the pinion down to cure it under load . 5 degrees is probably a bit much but if that's what you have I'd give it a try . A picture from the side view of your driveshaft (driveline angles) might make it easier to diagnose . 50mm lens or longer will help with the aspherical distortion .

 

[kfa670]

It doesn't completely go away if I let off the gas but it noticably improves. If I'm coasting down the street, and I just very lightly touch the throttle, I can make all the rumble completely disappear. I've been reading a little about measuring the flange angles and seeing how far away from parallel they are, but I'm at work and will be for the next week or so. When I'm home I'll try and get some pics and measurements. I currently don't have any shims.

 

[kfa670]

Ah, and after a little more careful reading, Bandi's shims he was talking about for the front. Which he didn't end up using cuz castor built into the lift design. Which on mine the front is great. SO, apparently i get to tear the drive line back out when I'm home and measure my flange angles. Pretty sure its not anything in the T-case or axle because both flanges were nice and tight/smooth the last time I had the line out.

 

[62LostInMn]

I shimmed my rear axle to get rid of drive line rumble. Worked great. I read through this info

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Measurements

to understand the problem. My lift is 2-3" OME Medium and I used 3 deg shims (from 4Crawler) based on my top and bottom flange measurements - no need to pull the drive shaft. Remember the fat end of the shim points toward the shackle. It's nice and smooth now. Good Luck.

 

[kfa670]

Thanks for the input lostinmtn. I ordered some new matsuba u-joints cuz i figured I haven't changed them since I've owned it and If i'm pulling the drive line I may as well do it. My rumble started less noticeable than it is now after the lift install. It used to completely disappear after about 45 on the highway but now there is a faint high pitched ZZZZZzzzzzzzzZZZZZZZzzzzzz sound that kind of increases and decreases in audibility as you cruise. Down around 25 under slight load going through town, especially up a small incline, the rumble/shudder is incredibly annoying. Rattles everything in the console. Can't be good for bearings. If anyone else has some advice I more than appreciate it! I'll have to report back with my flange angles once I make it home.

 

[RunTrout]

I've got OME 2-3" springs and long shackles (i know i know...),
Axle shims in the rear helped, but it still rumbles a bit around 25.

 

[lcwizard]

really curious about this. i've done seven trucks , no vibration. Only front end variations. Sometimes with a
high mileage truck the u-joints set a pattern and only replacing them will work with a lift

 

[RunTrout]

I have new u-joints in a box, but no press, and no money to get it done right now...
Shims are cheap! Hopefully the new u-joints will fix what is left of the vibration.

 

[lcwizard]

what happens when you run it 90 degrees out of phase?

 

[kfa670]

Hey lc, I'm hoping to be back home from work by this weekend, so I will be able to get some measurements. Should have looked into this a little sooner maybe.... but I was having too much fun with it after the lift. The more I think about it, I have to admit my u-joints may not be in as good of shape as I believe them to be, and that could be causing part/all of the problem. The vibration is definitely becoming more and more noticeable, so if the u-joints were pattern worn, it could be compounding the wear and making it worse the more I drive. Hoping the problem isn't a more costly/serious one lol

 

[RunTrout]

what happens when you run it 90 degrees out of phase?

Dude, you're the wizard (i.e. tell us please)! I don't know, thought they were supposed to be in phase. Have you had success running at 90 degrees? might be worth a try. I'm not going to mess with it until I can get new ujoints pressed in.

 

[franklin40]

have 2 1/2 inch OME lift with extended man-a-fre shackles and had a terrible vibration. measured off the top of the flange and put in shims to correct it. was just as bad. ended up dropping the drive shaft (ten minutes of work) and found the measurement off the flanges wasn't right so remeasured and replaced with new shims. vibration gone. it made a difference within 1.5 degrees. i too balanced driveshaft replaces u joints etc. my rear pinion angle is finicky. the front tolerated 3 degrees off no problem vibration wise but the back is needs to be really precise.

good luck. it nearly drove me nuts.

 

[lcwizard]

Dude, you're the wizard (i.e. tell us please)! I don't know, thought they were supposed to be in phase. Have you had success running at 90 degrees? might be worth a try. I'm not going to mess with it until I can get new ujoints pressed in.

I'm curious the result. Front FJ80 shafts are, many times, 90 out from the factory
and vibrate badly in phase. Don't know what the explanation is. Every driveline shop I've had 80 work done doesn't believe it's possible. Only takes a few minutes so what the hell. I have the same springs on two of mine without shimming

 

[kfa670]

When i take it out for measuring i will the give the 90 out a try.

 

[kfa670]

Leaning more and more toward bad u joints.... fingers crossed

 

[redcorn]

Check your pinion nut as well.....sounds like a loose nut to me

 

[kfa670]

Pinion and t-case flange angles

Ok, got a chance to measure my angles but not a chance to try much else as I only had a few days off. The one that measures about 89 degrees is at my t-case, and the one that measures about 84 or so is my pinion. So from what I can gather from these two measurements, this could be the cause of my vibration? And some 4-5* shims should get my flanges closer to parrallel?