Absolutely. The dampening material is only a band aid for sure, the root cause of the vibration needs to be stopped.
4.0, 42RLE, NP241OR High Speed Vibrations After Re-Gear to 4.88 or Deeper
- Thread starter Mr. Bills
- Start date
Absolutely. The dampening material is only a band aid for sure, the root cause of the vibration needs to be stopped.
I was thinking in the same lines when I installed my Barnes skid, hoping that the thicker skid would make it more rigid and change the resonant frequency that the stock shovel was making. That, and raising the drivetrain up 1" would lower the angle of TC input yoke. Sadly, nothing changed as a result.
jeepndogs
TJ Enthusiast
Actually tried putting a 1/4 rubber spacer between the Skid plate and the frame. No change. Also took a vibration damper assembly that ford uses on the rail of I think it was a new escape and bolted that to the skid just to see if it would absorb any of it.
Yeah, I can see that doing something...wouldn't hurt to try it anyway, especially on a joint that was the same size in both directions.
So, for 90* out of phase, one end of the fixed ears are horizontal, and the other vertical? This is with the drive shaft laying flat on the ground.
I also found this video on youtube - there is NVH app released by the Weber State University - Department of Automotive Technology - Transmission Lab. It's ultra expensive at $400 but look at what it finds.
$400 isn't bad if it solves this mind numbing problem so many of us seem to be facing!
I feel it’s just a fancy calculator, there’s no way with him holding the phone the sensors are sensitive enough in just your phone for those readings to be accurate enough where they would be useful.
I'd be real careful putting any stock into what that guy is saying. His video is full of errors and poor statistics. For instance... He said all of the problems are high speed, but they spent most of the time AT high speed. They should have spent an equal amount of time at each speed, or factored the occurrences by the amount of time in that speed bucket.
It's like saying 90 percent of accidents happen within 30 miles of home. Your probability of being within 30 miles of home is MUCH greater than being further away, so of course most accidents happen there.
Also... They MUST have some sort of accelerometer for data collection. There isn't any way the phone is able to separate all those different signals.
I found this on another forum and I think it's very relevant here. The OP on that thread was fighting a vibration issue that happens in overdrive gear on his 42RLE on a lifted TJ (otherwise stock with no regearing etc). Link to the full thread here:
https://bit.ly/2Svc9O0
It was Jim Frens, the owner of Nth Degree about 2 years ago in an email to me I subsequently posted on ROF. Here's the relevant part:
"Vibration problems in ‘03+ Wranglers are mostly due to poor decisions that were made at Jeep several years back (when engineering the ‘03’s started). The stock center skid for ‘03+ TJ’s has a natural frequency that lines up with the normal powertrain vibrations, and so acts as a ‘speaker’ to make this energy very apparent in spite of the rubber isolators. The other problem is that your new 42RLE automatic is derived from the FWD transaxle in the Dodge Stratus/Cirrus cars, and unfortunately has their carryover gear ratios (way too wide with a horrifically tall OD ratio of .69:1). And guess what? The OD ratio sets up a harmonic with the third-order firing frequency of the I-6 engine because they are only 2% apart, so you have a powertrain that just loves to ‘sing’ – and the only part of it you can do anything about is the center skid, which is why it’s been learned that changing out the center skid does help a bit (removing the speaker by changing it’s natural frequency, since the natural frequency of the beefier skid is much higher – this applies to both the RELA skid and our Tummy Tucker). " [I am sure this is the case with other skids also - Jerry] "Vibration problems in a lifted vehicle are only about 25% dependent on the balance of the driveshaft itself and it’s operating angles, the rest is natural frequencies, etc. – unfortunately virtually none of the end-users w/ lifted TJ’s know anything about this and so get mad at whatever they think is the culprit – and in fact no one thing usually is – Jeep did some things that didn’t help, and the lifting certainly didn’t help, and incorrect set-up of the lifted suspension only adds to this mess, so there’s much more than meets the ‘eye’ (or in this case your *** feeling the vibes!)."
I'm wondering if any of you with vibration issues already have, or tried using a differently sized/weighted aftermarket TC skid. I suspect Jeeps with manual trans are also susceptible to this problem but at a smaller scale.
The reason why some 42RLE Jeeps show the problem and others don't could be just due to small variations in the weight of frame/TC skid combo in production that only puts some Jeeps past the critical point. Or that serious Jeep owners, who do regear, already have a tummy tuck or some other aftermarket skid plate and therefore have alleviated the issue when before regearing. If this is the cause of our problems, no amount of driveshaft balancing or pinion angle adjustment will fix the problem.
@Mr. Bills do the vibrations in your Jeep go away or reduce if you turn off overdrive? I ask because I don't have my Jeep to check, it's still at Jeep West.
This maybe a stupid question, but what would happen to the vibration if one removed the TC skid entirely and went for a test drive (with and without engine the OD if possible)? Is this easy enough to try for someone on the forum here?
Comments @Chris @bobthetj03 @Mr. Bills ?
https://bit.ly/2Svc9O0
It was Jim Frens, the owner of Nth Degree about 2 years ago in an email to me I subsequently posted on ROF. Here's the relevant part:
"Vibration problems in ‘03+ Wranglers are mostly due to poor decisions that were made at Jeep several years back (when engineering the ‘03’s started). The stock center skid for ‘03+ TJ’s has a natural frequency that lines up with the normal powertrain vibrations, and so acts as a ‘speaker’ to make this energy very apparent in spite of the rubber isolators. The other problem is that your new 42RLE automatic is derived from the FWD transaxle in the Dodge Stratus/Cirrus cars, and unfortunately has their carryover gear ratios (way too wide with a horrifically tall OD ratio of .69:1). And guess what? The OD ratio sets up a harmonic with the third-order firing frequency of the I-6 engine because they are only 2% apart, so you have a powertrain that just loves to ‘sing’ – and the only part of it you can do anything about is the center skid, which is why it’s been learned that changing out the center skid does help a bit (removing the speaker by changing it’s natural frequency, since the natural frequency of the beefier skid is much higher – this applies to both the RELA skid and our Tummy Tucker). " [I am sure this is the case with other skids also - Jerry] "Vibration problems in a lifted vehicle are only about 25% dependent on the balance of the driveshaft itself and it’s operating angles, the rest is natural frequencies, etc. – unfortunately virtually none of the end-users w/ lifted TJ’s know anything about this and so get mad at whatever they think is the culprit – and in fact no one thing usually is – Jeep did some things that didn’t help, and the lifting certainly didn’t help, and incorrect set-up of the lifted suspension only adds to this mess, so there’s much more than meets the ‘eye’ (or in this case your *** feeling the vibes!)."
I'm wondering if any of you with vibration issues already have, or tried using a differently sized/weighted aftermarket TC skid. I suspect Jeeps with manual trans are also susceptible to this problem but at a smaller scale.
The reason why some 42RLE Jeeps show the problem and others don't could be just due to small variations in the weight of frame/TC skid combo in production that only puts some Jeeps past the critical point. Or that serious Jeep owners, who do regear, already have a tummy tuck or some other aftermarket skid plate and therefore have alleviated the issue when before regearing. If this is the cause of our problems, no amount of driveshaft balancing or pinion angle adjustment will fix the problem.
@Mr. Bills do the vibrations in your Jeep go away or reduce if you turn off overdrive? I ask because I don't have my Jeep to check, it's still at Jeep West.
This maybe a stupid question, but what would happen to the vibration if one removed the TC skid entirely and went for a test drive (with and without engine the OD if possible)? Is this easy enough to try for someone on the forum here?
Comments @Chris @bobthetj03 @Mr. Bills ?
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@bobthetj03 recently changed his skid but I don't recall him saying it helped anything in regards to vibration/harmonics.
If there were a replacement skid that was 1) thicker steel or even aluminum, and 2) didn't necessarily raise the tc, but eliminated the shovel's ridges, I would bolt one up to test the theory. I experienced the harmonic vibrations quite a bit on the '03 X I previously owned, a to a lesser extent on the currently owned Rubicon. All at only 2" of lift, maybe 2.5" on the X. Both have the 42RLE. I agree with the above article, based on my experience with two post-03 TJs, that Jeep changed something, and the harmonic vibration is more prevalent on automatic TJs in those years. Lifting adds a new factor, and apparently so does re-gearing.
If the skid is the issue, ditch it as far as a mount and use a separate crossmember.
I have the Rokmen skid on mine, which is quite heavy and very stout. I still had the vibration after re-gear though, so the skid doesn't appear to have done anything to solve that. Of course my vibration could be easier to figure out than yours, but we'll see what Dave says.
Does an aftermarket skid plate exist that can be used in a TJ without installing a body lift?
@glwood very interesting to hear about your previous X. You had only a suspension lift and otherwise no major modifications on that Jeep? Do you recall at what speeds/engine rpms did you experience the vibrations kick in?
@glwood very interesting to hear about your previous X. You had only a suspension lift and otherwise no major modifications on that Jeep? Do you recall at what speeds/engine rpms did you experience the vibrations kick in?
The skid plate I installed only raises the TC up 1", so I would imagine that you could use this skid without a BL. Rubi models maybe due to the bigger TC.
Even on a Rubicon, I think there's enough room to raise it 1" without hitting the tub. At least from looking under mine I came to this conclusion. You will of course probably get more noise from this, and the exhaust hanger will need to be cut down about 1" as well.