Pushing axle back slightly? - JeepForum.com
 
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post #1 of 13 Old 06-09-2019, 12:15 PM Thread Starter
WeezyBlue
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Pushing axle back slightly?

I have a Savvy 4" lift on my TJ, it's been on there for about 5 years now. Two years ago I went to 37s and armor/fenders. Even though tires cleared fully when doing all the clearance tests in the driveway with coils in/out, articulating in both directions, in reality on the trail they rub in the rear, just enough to take the paint/powdercoat off in the front of the wheel well, and enough to dig in pretty good and make some terrible sounds in the rear of the wheel well.

I had already cut the tub channel forward and hammered the pinch welds at the front of the rear wheel well, and they don't make contact there, but they do just barely rub the outer edge of the corner armor/tub where highlighted in the photo.

At the rear of the wheel well they make contact about 1/4" overlapping onto the armor/tub. I had originally planned to open this area up anyway but when my clearance testing seemed ok, decided not to cut the steel.

Now I have a Savvy gas tank skid arriving in the next couple days and I'm considering pushing the axle back maybe 1/2 to 1" to make clearance at the front (provided gas tank clearance,) and cutting the rear of the opening as necessary.

My concerns are as follows, is there enough thread left engaged in the upper arms to do this, if I split the difference between the two joints? Next concern is the amount of spline I would have left in my Tom Woods shaft. It was made ordered to the exact length it sits at now, would extending at 1/2 to 1" be too much?








Couple notes about the photos, all the oil everywhere is from the transfer case. I just replaced the rear extension housing seal and is no longer a problem. Also you can see where my frame end lower control arm bolt has been moving... so that bolt is going to be coming out to inspect the mount anyway. If that hole is wallowed out badly, I may lean towards just going Savvy mid arm.

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post #2 of 13 Old 06-09-2019, 12:29 PM
biffgnar
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The real issue is that with TJs 37s need wider axles.

As far as driveshaft length. You aren't lengthening it that much. Play with a right triangle calculator to see how hypotenuse changes when one leg is changed.
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post #3 of 13 Old 06-09-2019, 02:41 PM
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Not sure if there's enough room back there to move the axle back an inch without having the rear track bar hit the gas tank...
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post #4 of 13 Old 06-09-2019, 03:06 PM Thread Starter
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Secondary question for you guys, about my control arm shifting. I didn't have a problem for 4 years until I took my Jeep to get regeared. I'm guessing they pulled the axles from under the Jeep. Maybe the Currie bolt got screwed up by the stover nut, or they over torqued or under torqued, but the bolt just won't stay tight now. I was on a 800 mile trip when it started clunking and hopefully it's not wallowed out now.



I believe the Currie torque spec for that bolt is 90 ft-lb. FSM says 130 ft-lb.

I have an unused Currie 9/16 grade 8 fine thread bolt, the general max torque I see quoted for that bolt is 170 ft-lb dry. I don't see a downside to swapping them out and cranking it up to 170 unless that will somehow cause damage to the johnny joint itself?



Quote:
Originally Posted by biffgnar View Post
The real issue is that with TJs 37s need wider axles.

As far as driveshaft length. You aren't lengthening it that much. Play with a right triangle calculator to see how hypotenuse changes when one leg is changed.

Wider axles or stronger axles? I know strength is an issue for most.

Good point about the different angles, I'll have to lay under it and kind of work that out in my head.


Quote:
Originally Posted by Shark_13 View Post
Not sure if there's enough room back there to move the axle back an inch without having the rear track bar hit the gas tank...

The Savvy tank is supposed to offer more space, but I don't know by how much. When I set the arms initially I had to go all the way in with the lowers in order to get the pinion angle right with the flat tummy tuck and center the bump stops perfectly, so I never really paid attention to the clearance behind the tank. In reality it only needs to go back a small amount to cure the clearance issue at the front of the wheel wells. It does have the Currie angled track bar bracket welded on as well.

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post #5 of 13 Old 06-09-2019, 03:58 PM
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Wider.

From what I have read, once you go over 35 you might as well build for 40's because to get 37's to fit you are going to 1 tons.



Quote:
Originally Posted by WeezyBlue View Post
Secondary question for you guys, about my control arm shifting. I didn't have a problem for 4 years until I took my Jeep to get regeared. I'm guessing they pulled the axles from under the Jeep. Maybe the Currie bolt got screwed up by the stover nut, or they over torqued or under torqued, but the bolt just won't stay tight now. I was on a 800 mile trip when it started clunking and hopefully it's not wallowed out now.



I believe the Currie torque spec for that bolt is 90 ft-lb. FSM says 130 ft-lb.

I have an unused Currie 9/16 grade 8 fine thread bolt, the general max torque I see quoted for that bolt is 170 ft-lb dry. I don't see a downside to swapping them out and cranking it up to 170 unless that will somehow cause damage to the johnny joint itself?






Wider axles or stronger axles? I know strength is an issue for most.

Good point about the different angles, I'll have to lay under it and kind of work that out in my head.





The Savvy tank is supposed to offer more space, but I don't know by how much. When I set the arms initially I had to go all the way in with the lowers in order to get the pinion angle right with the flat tummy tuck and center the bump stops perfectly, so I never really paid attention to the clearance behind the tank. In reality it only needs to go back a small amount to cure the clearance issue at the front of the wheel wells. It does have the Currie angled track bar bracket welded on as well.

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post #6 of 13 Old 06-09-2019, 05:03 PM Thread Starter
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I did find some info that suggests 1.5x the diameter of the shank to be threaded into the arm, but can't find any actual spec on the threaded length on those joints, so I'll just have to thread one out and measure.


Quote:
Originally Posted by rikkards View Post
Wider.

From what I have read, once you go over 35 you might as well build for 40's because to get 37's to fit you are going to 1 tons.
I guess I don't really grasp that concept, everything clears to the inside save for the tires rub the lower control arms in the front, right at full lock. Still have most of my steering, has never been an issue. And front-to-rear clearance is only a problem for that 1" cumulative at the rear. This is just on the 4" Savvy lift on the bump stops with a 1.25" body lifts and fenders, including an inner fender kit for the front. Wheels are 3.63" backspace and I stay connected with the Antirock in the front and factory rear.


I know it has it's shortcomings for sure, but up here in MN I just air down to 5 psi and it idles everywhere I point it. I've been waiting for something to break to justify new axles but they just keep going.




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post #7 of 13 Old 06-09-2019, 08:45 PM
UTWeezul
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Id personally just trim the body and not bother moving the axle back.
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post #8 of 13 Old 06-10-2019, 05:12 AM
biffgnar
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On the width point you need to envision the arc that the axle moves in. That pulls the tire in to the tub. 37s need to be pushed farther away (i.e. out) from the tub to make room and maximize travel. Yes, you can set bumpstops so all good, but you probably have less travel than you would if you mounted up 35s. I know I would have less if I put on 37s.
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post #9 of 13 Old 06-10-2019, 06:48 AM
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I wouldn't go any further out on those control arms. Trust me on this: https://www.jeepforum.com/forum/f9/w...l#post40590075
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post #10 of 13 Old 06-10-2019, 07:59 AM Thread Starter
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Quote:
Originally Posted by UTWeezul View Post
Id personally just trim the body and not bother moving the axle back.
Very little material at the leading edge of the wheel well before you get into the tub weld.



Quote:
Originally Posted by biffgnar View Post
On the width point you need to envision the arc that the axle moves in. That pulls the tire in to the tub. 37s need to be pushed farther away (i.e. out) from the tub to make room and maximize travel. Yes, you can set bumpstops so all good, but you probably have less travel than you would if you mounted up 35s. I know I would have less if I put on 37s.

biffgnar, I've read a lot of good stuff from you on here and I'm not doubting your knowledge, help me understand where my logic is breaking down.

If I had wider axles using the same mounting points, rotation and arc of the axle would remain the same. If you drew a centerline down the middle of the axle tubes, along the shaft, that angle or location in space would not change. It would only be extended out by wider axles. With any given tire size that clearance measured from the center of this line would remain the same along the length of that line. I wouldn't get any more clearance where I'm making contact with the tub by making the axles wider, unless I went wide enough to push the inside edge of the tire past the outside of the tub, maybe 16" wider total. It would allow more travel at the tire itself under articulation, however, as that point is extended outward.

Unless the advantages of the wider axles themselves is actually the fact that the tubes are thicker, pushing that axle centerline downward, and increasing the radius of the axle's movement. Or that we're changing other factors in the suspension along with this, like mounting points.

As it sits, it's just a Savvy 4" kit, all factory mounting points. The bump stops that came with the kit stop the upward travel at coil bind. With factory fenders that allows clearance for 35" tires. By opening up the front fenders and losing the rear flares I've (almost) made enough room for the 37s. The rubbing in the rear I'm talking about in this thread doesn't limit the travel, the bump stops are still doing that. It's just making noise and tearing up paint. The bumps stops are still stopping the travel at coil bind. It still has the same full range of motion it had when it was on 35s.




Quote:
Originally Posted by JEK3 View Post
I wouldn't go any further out on those control arms. Trust me on this: https://www.jeepforum.com/forum/f9/w...l#post40590075

Ouch. Going off the diameter x1.5 rule I see so often stated for thread engagement you didn't have much threaded in there. But your number of exposed threads look similar to mine, so I might be in the exact same situation right now. What arms were those?

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post #11 of 13 Old 06-10-2019, 08:02 AM
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Quote:
Originally Posted by WeezyBlue View Post
Ouch. Going off the diameter x1.5 rule I see so often stated for thread engagement you didn't have much threaded in there. But your number of exposed threads look similar to mine, so I might be in the exact same situation right now. What arms were those?
Currie. Old school, from before Savvy came out with the double-adjustable version.
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post #12 of 13 Old 06-10-2019, 04:56 PM
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Axle mounting points will not be the same relative to the tire. There will be more tube outside the mounting point changing the arc of movement. I'm talking about something like 65" WMS to WMS. 2" plus per side. What can seem like just a front to back clearance issue has a lateral component to it also. It may not fix your issue, but your current setup is not helping at all.
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post #13 of 13 Old 06-10-2019, 07:35 PM
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Quote:
Originally Posted by WeezyBlue View Post
Very little material at the leading edge of the wheel well before you get into the tub weld.
From what you circled you arent cutting much. I did it on mine for clearance and never got into the weld at the tub and wheel well.
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