[LuckRider]

To those who have the 42RLE 4speed automatic Transmission, please take part in this poll. Here is the problem:

Who here has a whirling noise associated with a vibe in somewhere around 40-60 mph? Here is a description of the issue:

Vibrations on an 03+ automatic trans TJ

There are several ‘built in’ vibration problems with ‘03+ TJ’s – though ironically the biggest one is usually solved by ditching the factory center skid because it ‘drums’ in response to normal powertrain vibes (which the engine/trans mounts usually absorb). If you have an automatic trans, there is a wavering ‘droning’ sound that happens whenever the trans is in OD – because the .69:1 ratio aligns with the third-order firing frequency of the I-6 engine – you can’t escape this issue except to use the OD lockout button to keep the trans from shifting into OD so prematurely. If this sounds like your issue, try hitting the OD lockout button while driving between 45-55mph and see if it makes the issue go away – then you know what it is.

Who the info came from:

About Nth Degree Mobility

About the guy who designs the products:

• 2 engineering degrees...
• 9 years at a major OEM auto maker (guess which one?) doing
suspension tuning & development among other things...
• A passion for off-roading...
• A quest to make the best products for your modified Jeep- with the best designs, best quality, best craftsmanship, and supported by the best sales and tech support staff in the industry!

About the rest of us:

• 5 gagillion years of cumulative off roading experience under our belts...
• The belief that if we work here hard enough we'll get all kinds of free crap...
• Our commitment to you to do our very best to make sure your experience in doing business with us is top notch!

I just wonder who has experienced this issue, and who has taken the steps to fix it. I have heard that the only way to rectify the issue is to replace the skid.

Edit: I forgot to thank Raskull from MyJeepTJ.com for hosting the info, and Nth Degree Mobility for the Information. Link to the info: http://myjeeptj.com/2008/11/08/nth-degree-jeep-tj-tech

[never monday]

while harmonics can be an issue

because the .69:1 ratio aligns with the third-order firing frequency of the I-6 engine

sounds more like a sales pitch.
My guess, the skid isn't strong enough to withstand the torque and flexes.

[LuckRider]

Which skid can't withstand the torque and flexes? It has been noted that the stock skid provides very good lateral rigidity to keep the frame from flexing.

[never monday]

Originally Posted by LuckRider

Which skid can't withstand the torque and flexes? It has been noted that the stock skid provides very good lateral rigidity to keep the frame from flexing.

ok, but it's proven to be thin and dent easily. Thinner material will vibrate easier.

[RubiconRazorbac]

Haven't had a problem with that aspect of the 42RLE.

[jeepinmichguy_]

no issues with mine yet.

[dbbd1]

Hhhhhmmm, have not noticed it but I will try to listen for it next time out.

[LuckRider]

It looks like many have been spared of this issue. It gets very annoying at times.

[iceman8]

None yet. I am still under 20k miles so perhaps it's too soon. Also though, my tranny skid plate is currently off because the nutserts spun when I serviced the tranny and front driveshaft. I know the vibration you speak of, a GMC truck we have does it as well at certain speed/loads. Annoying.

[mrbates]

mine started at about 30k miles, i have the stock skid, and it has some trail abuse.

[silvanus]

I have it,and that droning sound is the torque converter. I haven't use my OD for the past three years and when in third it sounds like a digery doo, or Tibetan Monk. I've also removed the trans. skid because of the 4" lift I have on it.Didn't like the driveshaft rub. I'll soon be able to use the OD when I go to 4.88s later next month.

[TheBoogieman]

I never had any issues with mine.

[Unlimited04]

I know exactly what drone you're talking about. Every single 42RLE behind a 4.0L does it. If you don't feel/hear it then you don't know what you're looking for and haven't driven a Liberty with a 42RLE behind a 3.7L that does NOT do it. You can't really call it a vibration...because its not a pronounced feeling, you mostly hear it....and you mostly hear it between 45mph-55mph as the engine bogs down in the OD that is far too tall for the 4.0L. When you hear the engine bogging down...thats the drone. You can make happen in 2nd at low speeds too, if you don't accelerate throught it. The best medicine to eliminate the drone is a heavy foot and liberal use of the OD OFF button.

My mom's 06 LJ w/ 42RLE does it just like mine...although not as bad. I have a JeepMedic skid w/ factory mount and the drone is still there. Actually, my poly motor mounts & engine skid make it much more audible. You can make a similar drone with a NV3550 if you shift into 5th at like ~30-35mph and bog the engine.

[timberwolf0122]

I noticed the vine too it felt like the enterprises warp core at about warp 2 (next Gen). I figued it was resonance, since the lift I tend to kill the OD so I haven't noticed it much.

[never monday]

Originally Posted by Unlimited04

I have a JeepMedic skid w/ factory mount and the drone is still there. Actually, my poly motor mounts & engine skid make it much more audible.

blows my theory out of the water......