Rear Pinion Angle Issue, Vibration at 70MPH, New DC Shafts

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Dissent

Dissent

Questioning my life choices...
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10 Year
Joined
Sep 27, 2012
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270
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Location
Sweetwater, TN (East of Knoxville)
My 97 LX has a 50mm TJM Heavy linear spring kit with 30mm poly spacers on all corners. I've replaced all rubber bushings with OEM and have caster correction plates. Front alignment is complete and in spec. I've purchased both front and rear DC shafts from Curtis at Tatton Driveline through a recent group buy. My GRRR sound is gone in the front and rear now but I have a vibration that comes in at 58 and 70mph. I've ordered an angle gauge to verify driveline angles but i can see that the rear pinion to DC shaft angle is not 0 degrees and is possibly more than 1 degree. The vibration is definitely coming from the rear.

What inexpensive options to I have to fix this? I think upper and/or lower adjustable control arms would be the best solution but I have no cash for that. I have a 5000 mile road trip in 30 days and I'm worried about the vibration I have now becoming an issue during or after the trip.

Is there anyone who can chop, insert adjustments and reweld my stock arms quickly and cheaply? I'm about to be in a bind with the clock ticking.
 
Here's the current angle. Would more weight help? I don't have my sliders on yet and I'm running factory bumpers.

ImageUploadedByIH8MUD Forum1443480379.157182.webp
 
Is the vibe dependent upon acceleration vs deceleration? This variable can point to wheel bearings, pinion bearings, or transfer case output bearing. You could pull your rear shaft, lock up the CDL (if available) and drive without the rear driveline. (some FZJ people can confirm this?)

Have you rotated your tires to see if it changes at all?

With regards to your photo, the pinion angle should point level to slightly up in nature. it looks pretty level to me.
 
My understanding was that a DC shaft should be at 0 degrees, 1 degree max. I've not rotated the tires yet, will try that. The vibration comes in above 68 and maintains to 85, haven't gone any faster. Before replacing the rear shaft with the DC shaft, had a noticeable GRRRR just off throttle as the front did. I haven't pulled the rear shaft yet, I will after my angle gauge arrives on Thursday after I grab the angles to ensure they are/aren't in spec.
 
Now don't laugh... But do you have zerks on both sides oriented with each other? Meaning on the same side.
 
Yeah, I did check that on the new shafts.
 
Fixed: Rear DC shaft is at 5 degrees difference between shaft and pinion flange.
 
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When you state 5%, do you mean the difference between the transfer case output surface and the rear diff flange surface? And I assume you mead degrees, correct?
 
Sorry, it's 5 degrees difference between the pinion flange and the driveshaft (DC shaft).

I've decided that I'll have my original shaft worn splines looked at and fixed, rebalanced and put it back in along with a set of longer LCAs to get the pinion back to parallel with the transfer case and sell the new DC shaft.
 
Shop phoned back, my rear shaft splines are OK but the 1.5 year old U-Joints are worn, one fairly badly with some catching. I'm guessing the GRRR ate them? I'm getting 2x new OEM joints and rebalancing for about $300. I'll have a rear DC up for sale in late November!
 
I would be concerned with why the 1.5 year old U-joints are worn as well
 
One joint was installed by the shop backward which made greasing impossible. I didn't great every 3000 miles because it was a pain, maybe went about 6000 to keep in line with the oil changes. I will now religiously grease them every 3000 though. Getting new ones installed tomorrow.
 
Dissent said:
One joint was installed by the shop backward which made greasing impossible. I didn't great every 3000 miles because it was a pain, maybe went about 6000 to keep in line with the oil changes. I will now religiously grease them every 3000 though. Getting new ones installed tomorrow.
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Yea, I know it's a little late now, but did you try one of the long needle type adapters to grease it? I don't mean the one that looks like a hypodermic needle. It's about 1/8" diameter and about 2" long. just fits right over the little ball on the zerk. John
 
I didn't but I'm going to pick one up for the Front DC shad ball joint. I've created a maintenance reminder to stay on the 3K greasing.
 
I've installed the Metal Tech LCAs, preconfiguring them to be 3/8" longer than OEM. I used an angle gauge and set the transfer case output shaft at 0 degrees then put the gauge on the pinion flange and jacked it up until it also read 0 degrees. The front bolt slid right into the LCA without any trouble. Love it when I'm smarter than the truck!

For the record, the rear DC shaft I removed was sitting at a difference of only 1.55 degrees between the two flanges. The shaft was only a few degrees off from the 0 degree required (in line with the pinion flange). I had significant vibration from only 1.55 degrees. Amazing!

I bolted up the OEM shaft with new u-joints and balance and now the vibrations are gone from the rear. I'm nearly vibration free up to 80 MPH but I still detect a slight vibration from the front. I noticed that the front shaft is nearly straight so I will remove the DC shaft and measure the transfer/pinion angles then run without a front shaft to isolate while the new u-joints and balance work is being done to the front OEM shaft. I seriously think my GRRR problems after the lift were bad u-joints.

It's been an expensive lesson but at least I'm learning something! Probably going to put both DC shafts up for sale if the front works out OK.
 
I removed a 30mm spacer from the front, lowering it by 1" resulting in 3" lift in the front, maintaining the spacers and 4" lift in the rear to accommodate the weight. My handling and the wandering feel is noticeably better. Even with the caster correction plates, it was still floaty and is now very stable.

Lowering the front of course altered my LCA/Pinion work in the rear so I'll need to re-adjust them, no biggie.

The front however still is out of alignment and the DC shaft vibrates. The Pinion angle is better but still doesn't match the transfer case. I'm getting the OEM shaft refitted with new joints and balancing but I'm not sure if the resulting angles will cause vibrations with the OEM shaft. I feel like I'm in no-mans land where neither shaft is going to operate correctly.

Any predictions?

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You can use spacers to lower your tcase crossmember which will help with the angles. Start with .75" and see what that does for you.
 
murf said:
You can use spacers to lower your tcase crossmember which will help with the angles. Start with .75" and see what that does for you.
Click to expand...
Do you know the OEM size, length and pitch for the crossmember bolts by chance?
 
Sorry, I dont. We went to six points hardware and had them match up grade 8 bolt that were a little longer.
 
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