4.0, 42RLE, NP241OR High Speed Vibrations After Re-Gear to 4.88 or Deeper

Jerry Bransford said:
No vibrations with my 5.38's, 42RLE, and 241 tcase. Smooth as silk.
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What do you run for a tummy tuck? My front driveshaft gives off some vibrations at around 73mph with only 3" of lift, 4.56's, and 33's. I've heard that a tummy tuck would actually help with that. Is that the case? I'm specifically looking at Savvy if that makes any difference.
 
Thanks everyone for the input so far.

Lets try to keep the discussion in this thread focused on issues with vibrations/harmonics in jeeps with the 4.0l motor, 42RLE automatic transmission and 241OR transfer case experienced after re-gearing to 4.88 or deeper gears.

Vibrations experienced with 4.56 or numerically lower gear ratios are a topic for another thread.
 
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Mr. Bills said:
Thanks everyone for the input so far.

Lets try to keep the discussion in this thread focused on issues with vibrations/harmonics in jeeps with the 4.0l motor, 42RLE automatic transmission and 241OR transfer case experienced after re-gearing to 4.88 or deeper gears.

Vibrations experienced with 4.56 or numerically lower gear ratios are a topic for another thread.
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If I'm honest, I fail to see how vibrations with a certain engine, transmission, and transfer case are any different or special. In my view, you could swap the engine, switch to a manual, and put in a non-rubicon transfer case and still have the same vibrations assuming all the lengths and angles were the same. Deeper gears on any setup are going to make a Jeep more prone to vibrations.

But hey, maybe I'm missing something. Let me know if I'm wrong.
 
According to what I have found on the Interweb and in discussions with industry professionals generally recognized on this and other forums as experts in their field, the particular harmonic/vibration I'm chasing seems to be limited to jeeps with the 42RLE automatic transmission and primarily the 241OR transfer case and only after re-gearing to 5.13 or 5.38. I included 4.88 in the range for this discussion because that's where I started and where I had no vibrations.

If we expand the topic to any vibration at highway speeds with any gear ratio or any engine/transmission/transfer case combination I'm afraid the discussion will become too generalized and as a result less helpful for those with this specific issue.

At this juncture there isn't enough reported data to isolate the cause of the vibration/harmonic to driveline angles, driveshaft rotations/minute, slop or give in the transmission output shaft or transfer case internals, or any other particular factor. I'm not sure we will ever figure out the actual cause, however I am more interested in the fix and whether there actually is a fix short of converting to manual hubs.

My inclination at this point is to fiddle with my front pinion angles a bit more in an attempt to find a "sweet spot" that minimizes the harmonic, perhaps two more attempts, and if by that time no one has reported a fix that works short of converting to manual hubs then I'll just spend the money and get some hubs.
 
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Like others I've been down this road as well. I have a 03 Rubi, auto. It was stock - 4.10's, wheels and tires. I put in a 3" lift and the same vibes as described appeared. Spent countless hours without any change, did all the same things others have done. I was planning on the hub conversion, but decided to first install 33's, which I had planned to do anyway. Vibes disappeared, and no the stock tires where fine beforehand. The larger tires slowed the rpm's of the DS and vibes were gone. But 33's with 4.10's suck, but I'm afraid to regear to 5.13's and have the vibes come back.

So, it looks like, I probably will end up doing the hub conversion anyway, just so I can regear. ugggg

I keep holding out that some smart guy will figure this out once-and-for-all and I can avoid the hub conversion. So in the meantime I keep flipping the OD switch constantly.
 
This post by @jeepndogs in a related thread has some interesting detail: https://wranglertjforum.com/threads...bration-above-50-mph.4235/page-14#post-135314

jeepndogs said:
. . . I had the same issue but chose to do a hub conversion to stop the front shaft from spinning to solve it. I did however meet a guy at a Jeep event recently that was some sort of problem solver wizard for Jeep. Apparently he travels all over the country fixing issues other guys can’t. He also drives a lifted Lj on 35,s with 5.38’s. He took one look at my Lj with the hub conversion and the first thing he asked was if I did that to correct a vibration. After answering him he started to explain what he knew about the problem. He started with anything over 3in of lift starts to exceed the angle of the front cv joint. It’s not at its max but it lowers the RPM it can spin at without vibration. The gearing starts to exceed the joint RPM and causes the shaft to spin almost in an oval. Then the tolerance stacking starts to come into play. The shaft diameter isn’t large enough to prevent deflection so that starts to flex, then the front output of the TC starts to move around. The TC is mounted to a big flat pan and once the harmonics are transferred to the skid plate it resonates up into the tub causing the harmonic noise that is heard in the Jeep.

He claims the only way to stop it is to reduce the angle of the CV joint, slow the joint down, or stop it from spinning. He had raised the TC and said it actually decreases the angle of the front CV without adding too much angle to the rear. Absolutely no clue if any of this is really true but he sure sounded like he knew what he was talking about and I went for a ride in his Lj and there were no vibes and or noises at 75+ except for the tire noise from the MT’s.
/quote]
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So for the people who regeared and experienced vibs- Were there vibs before the regear with the OD off (at cruising speed with the same rpms with 4.10s in 3rd gear compared to 4th in the regear)?
 
Update 7/23/18:

I had the opportunity this past Saturday to drive 160 miles on the Interstate, do 85 miles offroad with the Mendocino 4x4 Club, then return 160 miles home. [A lot of driving for one day.]

My observations:

With matching front pinion and front driveshaft angles the vibrations I felt beginning at 67 mph after my re-gear to 5.38 are significantly less, enough so that on several occasions I found myself increasing cruising speed on the Interstate to 75 mph+ and not noticing the vibration/harmonic unless I was specifically focusing my attention on it.

It had been my intention to do this test run and then raise my front pinion angle slightly higher than the front driveshaft angle (in 1/2 degree steps) to determine whether the vibration/harmonic diminishes any more , but in checking steering response both at high speed (jeep tracks straight and steady) and at 25-30 mph (a bit slow to return to center) my caster angle is already reduced to the point where I don't want to lose any more. My current inclination is to leave things where they are for now.

Possible future conversion to manual hubs:

I am still interested in this option for several reasons, including (1) total elimination of the vibration/harmonic after the re-gear to 5.38; (2)better flat towing ability; (3) potentially being able to drive off the trail after an axle or u-joint failure by unlocking a hub; and (4) moving the "fuse" in the front axle assembly to a more easily accessible/replaceable hub.

This weekend I had the opportunity to speak with someone who converted to the Yukon manual hubs for the 5x4.5 lug pattern (Explorer hubs) and also the parts guy who sold the replacement parts when one of those smaller manual hubs grenaded on the trail. My take away was that if one is going to convert to Yukon manual hubs one should choose the larger hubs that require a change to the 5x5.5 lug pattern rather than try to stick with the factory TJ lug pattern.

More later.
 
Mr. Bills said:
Hard Top on. Its 110+ degrees in my area during the summer and I like my A/C.

The vibration/harmonic at 67+ mph that I experienced after my re-gear to 5.38 does not add to the noise level in any way that I can detect.
Click to expand...

Copy that.
 
Mr. Bills said:
Update 7/23/18:

I had the opportunity this past Saturday to drive 160 miles on the Interstate, do 85 miles offroad with the Mendocino 4x4 Club, then return 160 miles home. [A lot of driving for one day.]

My observations:

With matching front pinion and front driveshaft angles the vibrations I felt beginning at 67 mph after my re-gear to 5.38 are significantly less, enough so that on several occasions I found myself increasing cruising speed on the Interstate to 75 mph+ and not noticing the vibration/harmonic unless I was specifically focusing my attention on it.

It had been my intention to do this test run and then raise my front pinion angle slightly higher than the front driveshaft angle (in 1/2 degree steps) to determine whether the vibration/harmonic diminishes any more , but in checking steering response both at high speed (jeep tracks straight and steady) and at 25-30 mph (a bit slow to return to center) my caster angle is already reduced to the point where I don't want to lose any more. My current inclination is to leave things where they are for now.

Possible future conversion to manual hubs:

I am still interested in this option for several reasons, including (1) total elimination of the vibration/harmonic after the re-gear to 5.38; (2)better flat towing ability; (3) potentially being able to drive off the trail after an axle or u-joint failure by unlocking a hub; and (4) moving the "fuse" in the front axle assembly to a more easily accessible/replaceable hub.

This weekend I had the opportunity to speak with someone who converted to the Yukon manual hubs for the 5x4.5 lug pattern (Explorer hubs) and also the parts guy who sold the replacement parts when one of those smaller manual hubs grenaded on the trail. My take away was that if one is going to convert to Yukon manual hubs one should choose the larger hubs that require a change to the 5x5.5 lug pattern rather than try to stick with the factory TJ lug pattern.

More later.
Click to expand...


Just to add to this, the stock bolt pattern conversion increases the track width by 1 7/8 inches, the larg bolt pattern kit maintains the factory front track width. This was the main contributor to my decision to go with the big pattern kit.
 
Mr. Bills said:
The purpose of this thread is to provide a clearing house of information directly relevant to the the onset of high speed vibrations in a TJ/LJ Rubicon with 4.0l engine, 42RLE transmission and NP241OR transfer case after re-gearing to 4.88 or deeper gear sets..

Discussion of similar phenomena in jeeps with different transmissions, transfer cases or axles is a topic for another thread.

______________

My jeep: 2006 LJ Rubicon with 4.0l engine, 42RLE automatic transmission, 241OR transfer case, purchased from the prior owner with "metric 35" Mickey Thompson Baja ATZ P3 tires [315/75] and 4.88 gears. Currie Correctlync Steering, Currie Antirock Off-Road Swaybar, 5" lift.

My issue: After re-gearing from 4.88 to 5.38, I had a vibration or harmonic in or near the front end that began at exactly 67 mph and got worse as speed increased, enough so that if felt like it might vibrate my fillings loose when I tried to pass the 18 wheelers on the Interstate at 73 or above.

Posts on various jeep forums suggest that I am not the only one with this issue after re-gearing to 5.13 or 5.38. It appears to occur primarily (or only) in TJ's with the 42RLE automatic transmission and NP241OR transfer case.

My observations:

Immediately after the re-gear I noticed chirping from double cardan joint in the factory front driveshaft. The driveshaft was removed. I ordered a custom Tom Woods front driveshaft in lieu of rebuilding the u-joints in the factory unit. While waiting for a replacement no vibrations were noted.

The new driveshaft arrived in undamaged packaging and was installed. No vibrations were noted for several weeks because the gears were still new and during initial break-in I had been instructed to keep the speeds under 60. It wasn't until a few weeks after the new driveshaft was installed, after ring and pinion break-in was complete, that I drove faster than 65 mph and first noticed the vibration,which begins at exactly 67 mph and feels a lot like hitting a bad section of rain grooves in a concrete freeway. The vibration can only be felt through the steering wheel and not through the body, floor or shift levers. The vibration does not affect steering, which tracks straight and does not drift. The vibration does not increase much with increases in speed, if at all. Its there or its not.

The vibration did not change in mph at onset, character or intensity or any other way after any of the following:
a. Tire pressure adjustments
b. Re-balancing and rotating tires
c. Re-alignment (all within specs except caster, which was low as expected with a lifted rig)
d. Comprehensive professional inspection of all steering components, which are all tight, in good repair and well lubricated.

I had a telephone conversation with @mrblaine, who was aware of similar issues with other jeeps with 42RLE, 241OR and deep gears. He suggested that I check the front pinion angle and raise it if it was low.

My front pinion angle measured 10.5* My front driveshaft angle was 11.5*. The front [pinion angle was adjusted after which the front pinion angle and front driveshaft angle were both 11*.

I have only had time for an initial test drive. The vibration still comes on at exactly 67 mph but the intensity is considerably less after the pinion angle adjustment. I can now get up to 85 mph (as fast as I could go for the conditions that day) and the vibration isn't so bad that I want to immediately get off the throttle. However, there is still enough vibration to be an irritant at 67-75 mph cruising speeds.

I have a 300 mile round trip planned this coming weekend, which will give me ample time to record observations about how the pinion angle adjustment has changed the vibration. Its easy enough to avoid, just set cruise control at 65, but I would like to improve the situation after my return.

My plan is to raise the front pinion angle about 1/2* and observe any changes. Maybe the vibration will subside, maybe it will get worse, maybe it will stay the same.

If pinion angle adjustments can't fix this, I am open to any and all suggestions as to what to try next. I know I can "fix" it with money, i.e., converting to manual hubs, but I would like to try all the adjustments possible before I give up and go that route.

Your similar experiences?
What worked?
What didn't?
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I am running a 42rle and 4.88 gears and a 231 transfer case. I have only noted vibrations at around 45 miles per hour as soon as the torque converter locks up. Once above 55 in od no vibration at all
 
Jeepinjosh4.0 said:
I am running a 42rle and 4.88 gears and a 231 transfer case. I have only noted vibrations at around 45 miles per hour as soon as the torque converter locks up. Once above 55 in od no vibration at all
Click to expand...
Also to mention. I’m running a standard cv driveshaft and an 8.8 in the rear. Also have 4 inch lift with tcase drop
 
Wanted to offer my input on this thread since I recently had Revolution 5.38 gears installed in my 2005 Rubicon with the 42RLE transmission.

No vibrations whatsoever. I've driven it quite a bit since getting the gears installed, and even at highway speeds it's smooth as can be. Just thought I would chime in and give my feedback.
 
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