Noise on deceleration after SYE install

Tarmijo94

Tarmijo94

Member
Joined
Nov 1, 2018
Messages
65
Location
Arlington, TX
Hey everyone.

I finished my sye, dc shaft, upper arm install last week. First drive with it done went great, stayed under 40 MPH. Took it on the highway for the first time a few days ago and noticed a loud whirring sound with a minor vibration when I let off the gas at about 70 MPH. I feel like the jeep slowed down pretty quickly off the gas, but that may just be the fact that it was kinda windy and TJs aren't exactly aerodynamic. After hearing the sound on the highway, I continued to hear it while coasted at any speed about 35 or so, and I don't remember hearing it the first time out on regular roads, although I could have just not noticed it.

The car is:
1997 with 4.0,
32rh trans
3.07 gears Dana 35/30 with 31" tires (yes the gears suck)
advanced adapters SYE with Adams dc driveshaft.

I checked the pinion angle yesterday and I'm pretty sure they were within a degree of eachother, with pinion about .5 lower than shaft, but I'm going to check again today in case i confused myself reading the pinion angle subtracted from 90. I also noticed to play at the ujoints or axle yokes

Now, at the risk of telling on myself, when raising the pinion to install the upper arms, A placed the bottle jack under the pinion yoke and lifted from there.

I've done a lot of searching the forum, and havent quite found someone with the same problem.

Advice would be super appreciated,

Thanks.
 
Ok

The pinion and DS should be in a straight line. The rear pinion can take a little down, but never above the DS. It would really help if you could take a pic, from the side showing the TC output shaft and the pinion yoke.
 
MarkAlan said:
Ok

The pinion and DS should be in a straight line. The rear pinion can take a little down, but never above the DS. It would really help if you could take a pic, from the side showing the TC output shaft and the pinion yoke.
Click to expand...

Will post a picture when I get home from work in a few hours.
 
Exactly as mentioned above When you install a DC shaft, the 2 joints at the transfer case do all the work of making the angle down to the axle. The angle between the driveshaft and the pinion should be 0. If you have a little bit of downward angle in the pinion, it is probably close to OK, so you don't feel any vibes driving. But when you let off the gas, especially at speed, the drag causes the pinion to point down a bit more, and makes the vibe more apparent.

1553805944566.png
 
My bet is your pinion angle was set too low. Decelerating further lowers the pinion angle so if it's a little too low to begin with, it would get even lower during deceleration which would cause problems. The pinion angle should look exactly like in the illustration above in T's post.
 
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I did notice that the measurement spots on the rear of the axle gave me different readings. Not sure what that’s about


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Tarmijo94 said:
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I did notice that the measurement spots on the rear of the axle gave me different readings. Not sure what that’s about


Sent from my iPhone using Tapatalk
Click to expand...
I wouldn't worry too much about all the other angles of the axle. You mostly just want the pinion pointed right at the transfer case. And looking at the pics, it really looks like you are in pretty good shape. It might be just a touch low. Not enough that I would worry about really, but if you're getting vibes, there's nothing wrong with just trying to raise it a touch higher and see how it feels. I'm certainly no expert on these things, but it seems like you have quite a bit of splines showing. Certainly more than mine does, and I am also running one of Adam's driveshafts. I am wondering if the shaft is a little over extended and it's actually wobbling a bit? This is getting beyond my knowledge level, but it just has me wondering. If putting half a turn the upper control arms doesn't help your vibration, it might be worth sending a pic or two to Adam's?

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Jerry Bransford said:
I don't need an angle finder to see from your first photo that your pinion angle is too low.
Click to expand...

Okay. I’ll give it a turn or two tomorrow afternoon and test it out.

Should I be worried about the amount of spline in the driveshaft? Or just leave it unless the angle makes no difference?


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So I've gone and adjusted the upper arms, noise is still there. I took a new picture and a video. Its easily heard in real life i just hope it can be heard on video.

IMG_0909.JPG
 
The good news is your pinion angle is spot-on now. On the noise, I'm half-deaf so I'm not sure if I'm hearing what you're hearing but I heard a rumble then I heard a repetitive squeak. Either way neither sounds familiar.

Are the u-joints at both ends of the driveshaft centered and fully seated all the way inside their yokes?

u-joint.jpg
 
I was going to say the same thing. That's a lot of splines showing at ride height. Here's mine with a 3" lift and a 5 speed. Is the 32rh that much shorter?
20170707_081902.jpg
 
That is a huge difference, which is strange because i measured after installing the SYE and told them the number on the phone when ordering it.

Also about the caps, when first installing it, it wasnt seated correctly but caught it after a few bolt turns and reset it.
 
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