I am considering doing he rear frame mod (buttcrack) on my LJ. Does anyone have any pictures of the mod on an LJ?
Rear frame mod
- Thread starter NskLJ
- Start date
Can you send me a few
. Any tips also. I am about to tackle the shock outboard is this a good time to do it? It will save me from pulling he tank again.
This is a TJ but the concept is the same. Cut right behind the forward crossmember. Bolt up the rear section without the body lift pucks in place to set the height, preload upwards slightly since they don't have the shared tub weight on them. Or, alternately, measure the offset you need and set the height that way. In other words, if you remove a 1.25" lift puck, the offset will be 1.25". Make pieces to make it look like it came that way. If you would like some short sections of 2.5" wide frame material, I can make that happen.Can you send me a few
It is far enough rearward that it won't affect a normal outboard which typically places the mount in line with the forward shock crossmember.
LJ rear lift. Hesitant to post this because I am not sure I would do it this way, but it might give you some ideas. I do think what mrblaine posted above is stronger. That said, my Jeep is a more of a trail rig than a rock crawler and won’t be regularly bouncing the back off of rocks. I also wanted it to be very hard to tell the rear had been lifted, which lots of people don’t care about. The pictures also don’t show the plate I attached to the inside of the frame to strengthen the entire area. If worried about strength, one could attach a plate on the outside of the frame as well. I don’t have a picture of the finished product handy but it is very hard to tell it isn’t stock due to the way the frame curve is constructed.
On the LJ would you angle the frame up on the bottom since the frame curve is so far forward? On the plate you put on the inside of the frame did you use the half circle to avoid having a straight vertical weld that could crack?
I would like some frame pieces thanks for the offer. I am ordering some front reservoir mount from you this week, if you could throw them in the box that would be great.
Thank you for the picture. With the LJ the curve is forward in front of the other crossmember. I was interested in seeing if anybody did it this way. Looks like a lot of work. I think a reinforcement plate on the inside of the frame could be plug welded to keep the outside looking factory.
The inside reinforcement is edge and plug welded. Which is a real pain with body still on.
I can see that with the body on. I was thinking a reinforcement plate on the outside could be plug welded internally inside the frame.
You have to start with the offset pieces tacked in place and then do what appeals to your sensibilities. The bottom of the frame on the forward side is where you get to do the fancy work but on the TJU, you have to be mindful of your outboarding and figure most aren't going to be looking that hard at it anyway.
Yes, on the curve to stop a hard edge in a straight line. I normally curve them the other way but there was stuff in our way there.
Put a note in the comments so we upgrade the box size. A rough length would be helpful for the wedges. If the wedge is 8" long, that is one piece of frame material since you can cut both out of it.
Look closer at my pics. That gap we have is more than enough to get in there and weld most anything you want to.
Pull all the lower body mount bolts except the last ones at the front above the lower control arm mounts. Loosen those.
Pull the complete mount from under the grill.
Remove fan shroud screws.
Jack up back of tub until you can get a chunk of 4 x 4 on top of the frame right at the end of the torque box. Lower the body onto those to get lots of room to work back there with the tank out.
I did think of doing that, it may help with the clean up and welding of the shock towers also.
I was looking at the rear with that extra crossmember the the tank is mounted to. if I cut forward of it blending in the curve and filler pieces will be easier but I will have to add spacers to the rear of the tank skid. If I cut rear of the extra crossmember the filler pieces are longer but I think it it may be easier to get a fish plate on the back of the frame and tie it into the crossmember.
I would cut in front of the two crossmembers to get the extra ground clearance in addition to hiding the rear crack.
I combined raising the rear with raising the gas tank. Fairly straightforward to do-rather than adding spacers to the rear of the gas tank skid, cut the front of the tank skid off a few inches below where it attaches to the crossmember closest to the axle, overlap the cut off piece with the main skid about an inch, weld it up and reinstall. If you can manage the rear frame lift, raising the tank is very doable. Or go buy an aftermarket tank skid that is made to accommodate the rear frame lift. A little searching should turn up more information on how to do this.
I am trying to figure the best way to do this and not screw it up. I need a visual and the LJ has the extra crossmember the tank is mounted to. I try to run it all through in my head so I have a clear game plan before I start.
I went back a reread your post, maybe when I read it I missed where you stated behind the crossmember the tank is mounted to.
Similar threads
