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theksmith

laying under the jeep at 80MPH...

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Was this issue going on when you replaced your motor mounts?

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Was this issue going on when you replaced your motor mounts?

 

yes it's been a problem ever since the jk axle swap which is when i got new drive shafts and the 242hd as well. a lot changed at the same time.

 

i've replaced motor mounts twice i think since then. the slight lift of the engine from putting in new ones didn't really change things.

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the folks at Carolina Driveline had told me that they just started a large order while we were discussing exactly what i needed, and so it would be a week before they could even start mine. they did indeed get started last monday though, and it arrived exactly 7 days later.

 

just as asked for:

- 1330 CV with a 1350 style CV flange on the t-case end

- standard JK flange on the pinion end

- 2" diameter tube with .120 wall thickness

- grease-able joints

- super long travel design

 

including the $50 shipping from the east coast to AZ, it came to a total of $475.

 

it's right at the same collapsed length as the old shaft, so it will work fine up front as intended. fully extended it can hit 39", so it should also be safe at least for highway use as an emergency rear replacement. i'll have to measure how long my current rear gets when the suspension is fully drooped to see if it would work off-road there.

 

IMG_6132.JPG

 

i had a chance to install it tonight - check back tomorrow to find out if it solved my issues, was a waste of money, or something in between!

 

IMG_6158.JPG

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Nice, hope it works for you!

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and the verdict is...

 

the new driveshaft was worth the money. my vibe issues are about 90% fixed (and should be no more rubbing on the trans pan). i still have a pulsating vibration that comes on around 70MPH. however, the major mirror & seat vibration that used to come on at the same time (and only get worse with speed) is gone! seems that previous shaft really was bent/misaligned or whatever.

 

the pulsation that is left doesn't get worse with speed, it only pulses more frequently. i also have a slight vibration in the steering wheel that i think is the tires. i haven't had them re-balanced in a while, so i took them over to Tire Pros on Wednesday. turns out the first one on the machine needed so much that they had to order thicker weights (or else stack weights which is what most shops do, but i was happy to hear they wanted to do it right). so next week they should have the right weights in and i can get all the tires re-balanced.

 

in the mean time, i'm also going to try rotating each end that the drive-shaft mounts to 180*, one at a time. then if neither change makes any difference, rotate the whole driveshaft 180*. again, 90% of the problem is gone, but might as well try to dial in that last little bit!

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I'd like to go for a cruise & see the difference from last time.

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I'd like to go for a cruise & see the difference from last time.

 

come over any time!

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small updates on dialing it in...

 

i tried rotating each mating flange (t-case end and pinion ends) 180*, one at a time. this made no detectable difference in the minor vibes that are still present. i didn't really expect it to - sometimes people balance their yokes/flanges with a driveshaft, but i figured a modern machined flange isn't likely to be much off-balance in itself.

 

i had my wheels/tires re-balanced (had already rotated them myself recently). this did fix a slight vibe in the steering wheel that was really more of a very minor shimmy.

 

i also tried tilting my front axle backwards to see if i could now get a little of my caster back without increasing the vibes. i did one full rotation of the upper control arms, which was probably only 1/2 a degree of rotation. i didn't notice any improvement in the tracking (not that it's horrible really), nor any worsening of the vibes. i may try another full rotation, but first...

 

sometime this week i'm going to try temporarily raising and lowering my t-case by a small amount to see if that affects the remaining level of vibration.

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Did you check pinion angles on the front driveshaft, specifically that the angle of the pinion at the diff and the yoke at the TC are parallel? I had vibration issues with aftermarket parts on a rwd car, the pinion was -1 compared to the trans yoke. After shimming up the trans ~1/4" they became parallel. No more highway vibes.

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i forgot to ever update this - raising nor lowering the t-case 3/4" or so didn't seem to affect anything. i'm pretty happy living with the current small vibes that remain and so i'm moving on to other projects!

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