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post #1 of 34 Old 06-24-2017, 09:07 AM Thread Starter
Kalten
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Shakes, Shimmies and upgrades

I recently bought a 2006 LJ non-rubicon, had 77k miles on it and was used as a hunting rig. It has a 4" inch spring lift and the lower control arms have been replaced by aftermarket units. The rig is rolling on 33x10.5 on stock 15x8 wheels and 3.73 gear sets and an automatic transmission. The jeep was bought for my daughter to learn to drive in since she is intimidated by my Megacab and her school parking lot is very tight. Once she has moved out then the jeep will be my play toy. I do need to fix the problems and hopefully not create others.

Problem #1
I experienced a bout of death wobble during an afternoon commute home so I took the tires (BFG AT KO) in to have them checked and all were out of balance by a bit, the front passenger side by over 8oz. That tire is now my spare. I also ordered and installed a Synergy adjustable track bar (I have had good experience with there parts on my RAM). Now when I hit anything on the freeway that disrupts the front end it does a quick back and forth bobble and corrects itself. Should I be concerned and spend more time trying to eliminate any shimmy? I have a lower ball joint with excessive grease around it but it seems tight. I may just replace all of them, the axle u-joints and the unit bearings just to be up on maintenance.

Problem #2
With the front end mostly sorted out a new problem arose with regards the the rear drive area. At around 50 MPH while accelerating the jeep has a noticeable vibration, with or without the front shaft installed and with or without overdrive engaged, let off the gas and it goes away. I took the cheap option and replaced the U-joints to see if that would correct the issue and it did not. I checked the angles of the yokes and the driveshaft and the shaft is running at 7 degrees in comparison to the yokes and the yokes are parallel to each other. I also removed the rear shaft to ensure it was a contributing factor to the vibration. That leaves me with two other options. Swap the control arms so I can tip the nose of the pumpkin down a bit and/or install a SYE and new driveshaft. If I swap the control arms, would it be a good idea to swap the lowers since they are of an unknown origin and do not appear to allow much suspension twisting? If I do would it be worth the extra $100 per set to make sure they are adjustable, or should I just do all the adjustment with uppers? Still leaning toward Synergy arms since I don't think I would ever utilize the full potential of the Currie arms and I like the double adjuster setup of the Synergy.

Problem #3
While running with just the front driveshaft installed I get a bit of a vibration again at 50 but it goes away if I take it out of overdrive so I "assume" its from the low rpm while accelerating. I know I should re-gear but would I be best served by 4.10 or 4.56. I am leaning toward 4.56 so that in the future should I decide to run 35" tires it will handle them. Can you flat tow easily with 35" tires?

Are there any other thing I should consider doing? This will be mostly used as a DD and TOAD and while on vacations might see some light offroad duties. May get more extreme who knows what the future holds.

Thanks in advance.


2006 Jeep LJ Auto, 4" spring-lift, Synergy control arms and front trackbar, 33x10.5 BFG AT KO.
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post #2 of 34 Old 06-24-2017, 09:47 AM
biffgnar
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A front end that wants to wobble but stops is usually a sign of bad tires/wheel/balance. They are trying to wobble, but the rest of the front end is tight enough that it controls and stops the wobble. I know you said you had the tires balanced, but are you sure they got them to zero. Close is not close enough with bigger tires on a jeep.

With 4" of suspension lift you really need to have an SYE, double cardan rear driveshaft and adjustable control arms or a transfer case drop. Without either of those you will mostly likely have rear driveline vibes. Being an LJ helps, but at that height its still an issue.

For regear you want to go a lot deeper. The 42RLE transmission in that jeep has a 0.69 OD. For 33s, 4.88 or 5.13 and for 35s, potentially as deep as 5.89. But with your current axles, 5.13 is lowest you can go, so that's what I would do if I were you for either 33s or 35s.

If you are really considering 35s, I'd be thinking about steering and brake upgrades also.
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post #3 of 34 Old 06-24-2017, 12:38 PM
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I personally won't read crap that long. Biffgnar knows his stuff. Anything he says, do. He's a moderator for a reason. He is good at his Job and fair.
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post #4 of 34 Old 06-24-2017, 01:23 PM Thread Starter
Kalten
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Quote:
Originally Posted by biffgnar View Post
A front end that wants to wobble but stops is usually a sign of bad tires/wheel/balance. They are trying to wobble, but the rest of the front end is tight enough that it controls and stops the wobble. I know you said you had the tires balanced, but are you sure they got them to zero. Close is not close enough with bigger tires on a jeep.
I watched them do the balance and saw them zero out but I did not have a road force balance. I do know the tires are slightly out of round, about .030 to .040 on two of them. I would like to find someone to swap tires with for an hour to see how much of an effect it has.

Quote:
Originally Posted by biffgnar View Post
With 4" of suspension lift you really need to have an SYE, double cardan rear driveshaft and adjustable control arms or a transfer case drop. Without either of those you will mostly likely have rear driveline vibes. Being an LJ helps, but at that height its still an issue.
Standard SYE or super short if you had a choice?

Quote:
Originally Posted by biffgnar View Post
For regear you want to go a lot deeper. The 42RLE transmission in that jeep has a 0.69 OD. For 33s, 4.88 or 5.13 and for 35s, potentially as deep as 5.89. But with your current axles, 5.13 is lowest you can go, so that's what I would do if I were you for either 33s or 35s.

If you are really considering 35s, I'd be thinking about steering and brake upgrades also.
4.88 might work ok, when I ran the numbers through the calculator the 4.56 seemed closer to stock when the tires are taken into consideration but a little steeper would work too. What kind of brake upgrades? I was already looking at steering upgrades either the Currie or the Synergy. Though the Synergy will require new offset on the rims or larger diameter or wheel spacers. Will 35s destroy the Dana 30 in short order? Should I look for a 44?

2006 Jeep LJ Auto, 4" spring-lift, Synergy control arms and front trackbar, 33x10.5 BFG AT KO.
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post #5 of 34 Old 06-24-2017, 01:39 PM
Jerry Bransford
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Any tire that needs 8 oz. to balance it has a problem, that's a half-pound of lead. You definitely have a tire problem and I agree with biffgnar, your shakes and shimmies are highly likely to be caused by a bad tire or two.

For regearing, throw out the thought that you want the new gears to produce the same rpm that you had with the stock size tires. The larger the tire, the more rpms you need to turn them to keep the same performance. You couldn't turn 33's with the same performance at the same rpms that turned the small factory size tires.

For 33's, and ESPECIALLY due to the steep .69 Overdrive ratio in your 42RLE transmission, you need a minimum of 4.88 gearing. 4.56 would be a fine ratio choice for 33's and the 5-speed manual transmission but definitely not for your automatic. Your Overdrive drops the rpms down much further than most other transmissions do so you need to gear the axles to a lower ratio to compensate for that. 4.88 would be the minimum I'd go for and that will NOT give you high highway rpms... they'll barely be up high enough to cope with the 33's. Really. Personally, I'd go 5.13 which is ideal for 33's on the highway with the 42RLE automatic transmission.

It took us a few years to figure out the 42RLE automatic is a different beast due to its stupid-steep .69 Overdrive ratio and requires lower (higher number) axle ratios to cope with it. Trust us on this, don't look at the gearing charts and think we're smoking something funny.

Not to mention fixed gearing charts that don't take the transmission type into account don't show the rpms you'd see on the highway with any transmission with an overdrive, like your automatic or a 5-speed manual transmission. Fixed charts show the rpms you'd get with a 1:1 final drive ratio which would be with your overdrive turned off, a 5-speed shifted into 4th gear, etc. So if a fixed gearing ratio chart said you'd get 2700 rpms at 70 mph, you'd actually only be seeing 1863 rpms at 70 mph... .69x2700 = 1863.

When you have a choice, buy American made.
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post #6 of 34 Old 06-24-2017, 02:15 PM
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Quote:
Originally Posted by Kalten View Post
I watched them do the balance and saw them zero out but I did not have a road force balance. I do know the tires are slightly out of round, about .030 to .040 on two of them. I would like to find someone to swap tires with for an hour to see how much of an effect it has.



Standard SYE or super short if you had a choice?



4.88 might work ok, when I ran the numbers through the calculator the 4.56 seemed closer to stock when the tires are taken into consideration but a little steeper would work too. What kind of brake upgrades? I was already looking at steering upgrades either the Currie or the Synergy. Though the Synergy will require new offset on the rims or larger diameter or wheel spacers. Will 35s destroy the Dana 30 in short order? Should I look for a 44?
I think people should always go for super short SYE. It is a little more expensive and requires electronic speedo correction going forward, but the longer rear driveshaft is always a good thing.

The advice I gave about gearing is correct. 4.56 will not be a good choice. This has been discussed many times. Use the search function and read.

For steering Currie is a good upgrade that does what it needs to for most people. For brakes, at a minimum you want to think about a pad upgrade, but the Vanco big brake kits are awesome.

To run 35s, swap in alloy axle shafts for the D30 and it should be OK. You'll u-joints are almost always going to be the circuit breaker.
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post #7 of 34 Old 06-25-2017, 02:33 PM Thread Starter
Kalten
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Quote:
Originally Posted by biffgnar View Post
I think people should always go for super short SYE. It is a little more expensive and requires electronic speedo correction going forward, but the longer rear driveshaft is always a good thing.

The advice I gave about gearing is correct. 4.56 will not be a good choice.
After a bit more research I see the RPM difference is minimal at 60-70MPH. So yeah 4.88 will work just fine. I never contemplated that steep but what was said about the weight of the tires makes perfect sense.

I have a jeep superchips flashpaq that has speedometer correction (I didn't buy it, it came with the jeep. I removed any tuning that was put in with it and returned it to stock settings), many posts says it does not work since the 231 uses a gear. Any idea if it will work with a super short SYE? If not any reccomendation for one that will? Dakota digital, Speedo healer... any others?

2006 Jeep LJ Auto, 4" spring-lift, Synergy control arms and front trackbar, 33x10.5 BFG AT KO.
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post #8 of 34 Old 06-25-2017, 06:42 PM
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Quote:
Originally Posted by Kalten View Post
After a bit more research I see the RPM difference is minimal at 60-70MPH. So yeah 4.88 will work just fine. I never contemplated that steep but what was said about the weight of the tires makes perfect sense.

I have a jeep superchips flashpaq that has speedometer correction (I didn't buy it, it came with the jeep. I removed any tuning that was put in with it and returned it to stock settings), many posts says it does not work since the 231 uses a gear. Any idea if it will work with a super short SYE? If not any reccomendation for one that will? Dakota digital, Speedo healer... any others?
I believe superchips will not do a thing to help you. It is designed to change the PCM, but doesn't actually do anything for a TJ PCM. You need to change the signal to the PCM and that happens two ways - a different gear, when still gear driven, or something directly interrupting/modifying the signal from the TC to the PCM. My personal experience has been with Blue Monkey speedo healer. Good product.
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post #9 of 34 Old 06-25-2017, 11:04 PM Thread Starter
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So let me bounce this off the walls, just to make sure I have it all covered.

Phase 1, Super short SYE looking at JB conversions and a speedo healer. May as well do the teraflex 2wd low while I am in there. A tom woods drive shaft and the synergy upper control arms for the rear. That should take care of the back. Estimate @$1k-$1.2K

Phase 2, Rest of the control arms and the Currie JJ front end kit and currectlync steering. That should take care of the front. Estimate $2k

Phase 3, New gear sets 4.88 or 5.13 along with trutracs in both ends (not a fan of lockers for winter use on-road) and upgrade the front axles to alloy or RCV if they are worth twice the cost. Estimate $2k-$2.5k depending on who does the diff installs. I would love to learn it.

Phase 4, new tires and wheels 33-35" thinking 15x10 with -12 through -25 offset. will have to use the search function to see if it will work with 35s without major rubbing otherwise I'll stick to 33s. Estimate $1.5k-$1.7K

This will still be a vacation and off road capable rig but not a hardcore setup I just don't want to buy parts that will not be up to the tasks.

Did I miss anything vital?

2006 Jeep LJ Auto, 4" spring-lift, Synergy control arms and front trackbar, 33x10.5 BFG AT KO.
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post #10 of 34 Old 06-26-2017, 06:18 AM
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In Phase 1, I would consider a 1.25" body lift and 1" motor mount lift, paired with a high-clearance skid (tummy tuck). That would give you several inches of extra clearance under the middle, for only a few hundred extra dollars (with the SYE is the perfect time to do it). This was the first mod I determined that I "needed" after discovering that the skid can support the entire weight of the Jeep while taking all traction away from the tires.
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post #11 of 34 Old 06-26-2017, 07:01 AM Thread Starter
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I have never done a body lift or even really contemplated it. Will doing all three at the same time negate any affects on the radiator, or will it still need to be moved?

2006 Jeep LJ Auto, 4" spring-lift, Synergy control arms and front trackbar, 33x10.5 BFG AT KO.
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post #12 of 34 Old 06-26-2017, 07:39 AM
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I have never done a body lift or even really contemplated it. Will doing all three at the same time negate any affects on the radiator, or will it still need to be moved?
In terms of the fan in relation to the radiator: body lift moves the fan down, MML moves the fan up, tummy tuck moves the fan down.

The BL and MML generally cancel each other out. The tummy tuck can move the fan several inches. When I did all three, the net result was my fan is now about 1.5-2" lower on the radiator. I had to drill a few new holes to move the fan shroud down.

You shouldn't need to move the radiator itself. Moving the fan shroud to match the fan itself is sufficient, and can be done by just drilling a few holes.
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post #13 of 34 Old 06-26-2017, 09:52 AM
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Quote:
Originally Posted by Kalten View Post
So let me bounce this off the walls, just to make sure I have it all covered.

Phase 1, Super short SYE looking at JB conversions and a speedo healer. May as well do the teraflex 2wd low while I am in there. A tom woods drive shaft and the synergy upper control arms for the rear. That should take care of the back. Estimate @$1k-$1.2K

Phase 2, Rest of the control arms and the Currie JJ front end kit and currectlync steering. That should take care of the front. Estimate $2k

Phase 3, New gear sets 4.88 or 5.13 along with trutracs in both ends (not a fan of lockers for winter use on-road) and upgrade the front axles to alloy or RCV if they are worth twice the cost. Estimate $2k-$2.5k depending on who does the diff installs. I would love to learn it.

Phase 4, new tires and wheels 33-35" thinking 15x10 with -12 through -25 offset. will have to use the search function to see if it will work with 35s without major rubbing otherwise I'll stick to 33s. Estimate $1.5k-$1.7K

This will still be a vacation and off road capable rig but not a hardcore setup I just don't want to buy parts that will not be up to the tasks.

Did I miss anything vital?
pretty sure you don't need a speedo healer, you need to change the Gear in your Tcase as you have a Non rubi.

Sounds like everything else is a good choice. Hope all your dreams come true

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post #14 of 34 Old 06-26-2017, 10:54 AM
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pretty sure you don't need a speedo healer, you need to change the Gear in your Tcase as you have a Non rubi.
Note that he said a Super Short SYE. A Super Short removes the gear and converts the 231 to a tone ring (similar to a 241) and so does require a speedo healer.
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post #15 of 34 Old 06-26-2017, 11:41 AM
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Note that he said a Super Short SYE. A Super Short removes the gear and converts the 231 to a tone ring (similar to a 241) and so does require a speedo healer.
Hey Biff. Thanks. I did not notice that.

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