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Discussion Starter · #1 ·
Morning all. Need a little advice. 97 NAS 90. Rte 3” coils, fox reservoirs, Rte radius arms, Rte rear arms. 255/85/16 tires.
Truck has a vibration. Pulled rear shaft and it goes away. Drum is tight, pinion tight, rear output feels tight. Installed Tom woods Carman shafts front and rear.
Minimal change.
Thinking it’s a pinion angle issue. Currently it’s pointed mid way between parallel to the output and directly at the output.
Thinking next up is adjustable rear arms?
Anybody have any input on choices? Thoughts?
Thanks guys.
462146
 

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if it just came on, then probably one of the UJs. Tom wood— do you mean the are both double Cardan shafts? If so, that usually takes care of pinion angle and leads me to suspect UJ even more
 

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Discussion Starter · #3 ·
if it just came on, then probably one of the UJs. Tom wood— do you mean the are both double Cardan shafts? If so, that usually takes care of pinion angle and leads me to suspect UJ even more
It was there with stock shafts. Put double Cardon shafts on both ends still there. Slightly better. But not gone
 

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Tires rebalanced ? The rear rte arms are already corrected so your opinion angle should be pretty good. And went to double-card and shafts you should be fine as well.

Are they Tcase outputs 100% solid with no axial play? The roller bearings in there can wear out.
 

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Discussion Starter · #5 ·
Had the tires rebalanced twice and swapped out a set off one of my discoveries. T case outputs both feel really good. No discernible play.
Really a head scratcher
 

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Chasing vibrations suck. At least you e narrowed it down a little.
 

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AAA yellow `95 NAS D90 ST #2188
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Check Tom Woods site for correct pinion and Cardan set up.
Cardan should be at the TC end of shaft. Dif pinion should point to TC, parallel to shaft.

Switching to a cardan from a double UJ shaft will require axle to be rotated to get correct Pinon alignment. Adjustable rear links help but won't be enough to stop vibration. So the ball mount on the A link needs to be moved back with an adapter . This can cause the ball mount to rub through the gas tank causing a leak. The spring will look twisted but will work ok. The cardan will need greasing regularly and it's a bitch up on stands with a needle nose grease gun rotating the cardan

That's my experience on an NAS D90 with a 2 inch lift. If stock shaft works, keep it.
 

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It was there with stock shafts. Put double Cardon shafts on both ends still there. Slightly better. But not gone
You need to measure your exact angles. With a single joint shaft, both sides need to be within 3° Of each other. The rear shouldn't need a DC.


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But with a DC shaft, the pinion has to point directly up the shaft.

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Thinking it’s a pinion angle issue. Currently it’s pointed mid way between parallel to the output and directly at the output.
It’s impossible to verify your angles are good just by looking. Get one of these if you don’t have one.

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AAA yellow `95 NAS D90 ST #2188
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It was there with stock shafts.
Pulled rear shaft and it goes away
You might look for loose joints and damage on the original rear shaft. If you can, get it checked for balance too.
The new double cadan shaft will have its own new set of vibrations without correcting rear dif pinion angle.
If you find and correct problems with the original rear shaft, I'd swap it back in.
 
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