Any advice on installing replacement frame rails?

[Clarythedrill]

To all, I have ordered up replacement frame rails for my 2001 TJ that will go from the front control arm mount to the rear control arm mount. I am a decent welder, so I am not worried about that, and will be using cutoff disks to cut out the rusted frame rails. I also have jacks and jack stands to hold the transmission/transfer case while I have the mount removed for the replacements.

I guess my questions are for those who have done this, did you run into any issues that you had not accounted for once you got knee deep into the project, was it difficult to get it done with the brake lines right there in your way on the driver side, and lastly, how did you go about making sure that you welded the rails in the correct position so that the mount will bolt to the frame AND the transmission?

To solve the last question, I was going to tack weld the rails on both sides and then install the transmission mount and make sure everything is bolted up correctly and then finish welding the entirety of both rails. Anyway, I am open to any advice or suggestions. Thank you.

Edited for this last question- should I be worried about the frame "sagging" if I cut both sides at the same time, or should I cut one side and weld the new rail in before moving to the other side? I am just worried about the skid plate mounting holes not lining up if I do one side at a time.

 

[MutantNinjaTJ]

I would do one side at a time for just the reason you stated. And I would put the skid back on while welding. Then do the other side the same way. You might even consider tacking on a piece of angle iron as aback bone before cutting the damaged piece completely out to maintain it's position and to prevent sagging or separation spreading of the side your working on.

 

[Clarythedrill]

Mutant, thank for the reply. I am going to have to cut both sides where the three mounting bolts go, as those are rusted and just turn in the frame, so about 18 inches on both sides will be gone at the same time whether I like it or not, or I will not be able to drop the skid plate. I can use extra jack stands on the body to prop it up so there will be little to no sag i guess.

 

[Davidtj]

Not claiming to be a expert on this others can chime in
Are you going to butt weld it I think done properly should be sleeved which would mean taking body off remove rear axle etc cut frame sleeve and put together not sure how you could get good welds around whole frame with everything in place

 

[Clarythedrill]

David, the type of replacements I got are in a "U" shape, where you cut the lower 2/3s of the frame off then push the replacement up and over the leftover frame, then weld the top part on the outside and inside of the frame, and then the ends. The replacements sandwich over the existing frame. Nothing has to be removed other than the skid plate and then cutting out the rusted area of the original frame.

 

[MutantNinjaTJ]

Sounds like you got it figured out, now get off the computer and get to cutting before it gets too hot. And don't forget the "Col' Beers"

 

[Clarythedrill]

Mutant, I am actually away from home right now, and ordered the pieces a couple of days ago, and they are yet to arrive. I will be home on Tuesday, and they should arrive on Friday. I like to work everything out in my head and learn from others before I get busy doing something I have not done before. I will most likely post updates on this thread as I go, which will hopefully help anybody else who is thinking about doing a major frame repair.

 

[Not_Invented_Here_]

Good luck OP, report back with results and pics

 

[Clarythedrill]

NIH, I plan to do just that. My turn to contribute to this great forum.

 

[Davidtj]

David, the type of replacements I got are in a "U" shape, where you cut the lower 2/3s of the frame off then push the replacement up and over the leftover frame, then weld the top part on the outside and inside of the frame, and then the ends. The replacements sandwich over the existing frame. Nothing has to be removed other than the skid plate and then cutting out the rusted area of the original frame.

Got it was envisioning something a little different

 

[EJD]

Edited for this last question- should I be worried about the frame "sagging" if I cut both sides at the same time, or should I cut one side and weld the new rail in before moving to the other side? I am just worried about the skid plate mounting holes not lining up if I do one side at a time.

You would never cut both sides at the same time. Unbolt 3 bolts on one side with the transmission supported and then lower it so the skid plate is free from the frame rail it was bolted up to. Then cut off the section you intend to replace. Once that side is completely welded, jack the skid plate back up to that and button it up. Then move to the other side. It is essential to do it in this fashion otherwise you risk not having things line up correctly.

Also as a tip, get some weld-through primer/paint for the inside of the new frame rails and paint the parts prior to installing them, that way you have the insides coated and it should give them a little bit more rust protection.

 

[Clarythedrill]

You would never cut both sides at the same time. Unbolt 3 bolts on one side with the transmission supported and then lower it so the skid plate is free from the frame rail it was bolted up to. Then cut off the section you intend to replace. Once that side is completely welded, jack the skid plate back up to that and button it up. Then move to the other side. It is essential to do it in this fashion otherwise you risk not having things line up correctly.

Also as a tip, get some weld-through primer/paint for the inside of the new frame rails and paint the parts prior to installing them, that way you have the insides coated and it should give them a little bit more rust protection.

Good advice, thank you, but all the mounting bolts spin in the frame on both sides due to the rust. I will support one frame rail with jack stands to the front and rear of what I am cutting out, and only cut out the amount I need to to remove the skid plate instead of the entire length of the replacement rails. That should keep the frame from sagging on the side not being worked on.

 

[EJD]

Good advice, thank you, but all the mounting bolts spin in the frame on both sides due to the rust. I will support one frame rail with jack stands to the front and rear of what I am cutting out, and only cut out the amount I need to to remove the skid plate instead of the entire length of the replacement rails. That should keep the frame from sagging on the side not being worked on.

I don't think you'll have room for jack stands on the frame rails in front of and behind the section your cutting out. The new piece your going to weld on takes up that whole section basically from the front trail arm to the rear. I would just shear off the bolts that are spinning, then drop the skid plate on one side at a time. Your going to have to cut off the bolts anyway from the skid plate why not just do it from the start? Speaking of the bolts, make sure you have new bolts to reinstall the skid plate. The new frame sections don't all come with new hardware.

 

[Clarythedrill]

I don't think you'll have room for jack stands on the frame rails in front of and behind the section your cutting out. The new piece your going to weld on takes up that whole section basically from the front trail arm to the rear. I would just shear off the bolts that are spinning, then drop the skid plate on one side at a time. Your going to have to cut off the bolts anyway from the skid plate why not just do it from the start? Speaking of the bolts, make sure you have new bolts to reinstall the skid plate. The new frame sections don't all come with new hardware.

I was going to just cut out enough of the frame to remove the skid plate only, but I think you are right about needing to bolt everything in place prior to welding to ensure everything is located in the correct position. I do have one bolt on the passenger side that will unscrew, so I think I will be able to get it done if I start on the drivers side and use the single bolt on the passenger side and the transmission mount to locate and weld the drivers side first.

This is why I like getting multiple ideas, it helps be work it all out in my head prior to getting busy. I plan on getting it done over a four day weekend, so no big rush to get it done, and I have other vehicles do drive, so I want to go slow and do it right.

 

[Leinhit]

I I used interior frame treatment from Eastwood. It comes in a spray can comes out green. With a long straw. That's what I treated the inside of my replacement rails and The rusted frame after I was done welding. Then on the outside I used Eastwood's rust converting rubberized undercoat spray.

make sure you cut enough of the old frame out so the new piece will fit up tight. also on the backside of the replacement frame I cut about an inch of it off because I found that I couldn't get my welder up in there to weld it. By Lauren the back side of the replacement about an inch that gave me a little bit more room to weld.

 

[Clarythedrill]

I I used interior frame treatment from Eastwood. It comes in a spray can comes out green. With a long straw. That's what I treated the inside of my replacement rails and The rusted frame after I was done welding. Then on the outside I used Eastwood's rust converting rubberized undercoat spray.

make sure you cut enough of the old frame out so the new piece will fit up tight. also on the backside of the replacement frame I cut about an inch of it off because I found that I couldn't get my welder up in there to weld it. By Lauren the back side of the replacement about an inch that gave me a little bit more room to weld.

Yes, when I have the lower part of the frame cut out, I am going to treat the inside before welding the new piece in. I am also going to drill some drain holes in the frame to keep this from happening again. Next year I am moving to Texas, so should not be a problem after that. Just one more Chicago winter to go.