Frame Rot :(, What Are My Options?

[VorTekX]

After a hiatus I started working on my truck again only to discover that there is frame rot underneath the drivers control arm mount. the pictures shown are after I had hacked away at it and tried to pull as much stuff from inside the area. Was pretty upset about this. At this point, I would assume it would be best to through in the towel but I have already bought so many parts for this thing. The whole truck was pretty rusty so I had already acquired new fenders, doors, cab corners, floors, rockers, and a bed as well. I am still disassembling everything in order to overhaul the rest of the frame/ metal but before this I had not found any rot in other locations on the truck. Truck has a healthy running engine and always starts when I need it to. It has no other electrical issues.

 

From what I was thinking, I only have two options:

 

1. Continue stripping/wire wheeling the truck like I already was. If no where else has rot like pictured, I get a donor section from another MJ or even an XJ (If that's even possible?) and weld the subframe section in. 

 

2. If the rust ends up being way too extensive, just pull all the good parts/ drivetrain on it and find a roller chassis to reassemble it.

 

I had already purchased a mig welder and a plasma cutter in preparation for the cab so I do not need any additional equipment. I would just need to practice welding beforehand as its not something I have ever done. 

 

Looking to see if anyone else has had rot like this, and how did you handle it?

 

 

[The86manche]

It doesn't look great but id say its still fixable. I'd say grab a cherokee for a donor to make a patch for that area, or cut a chunk out to use as a patch.

[AZJeff]

12 minutes ago, The86manche said:

It doesn't look great but id say its still fixable. I'd say grab a cherokee for a donor to make a patch for that area, or cut a chunk out to use as a patch.

That’s a solid plan.

[eaglescout526]

12 minutes ago, AZJeff said:

That’s a solid plan.

Ha! Solid. 

[VorTekX]

28 minutes ago, The86manche said:

It doesn't look great but id say its still fixable. I'd say grab a cherokee for a donor to make a patch for that area, or cut a chunk out to use as a patch.

I know there were some minor differences between the MJs and XJs. Is control arm area the exact same or was the metal thicker on MJs?

[VorTekX]

Here is a picture of a 96 XJ I parted out a while back. As you can see the control arm area does not look at all like the MJ mounting area. That was my concern with sourcing an XJ for the metal. Did that mounting design change in the later years for the XJ? My MJ is an 88, if the XJs from 88 have an identical structure then it would work.

 

[89 MJ]

Do you want to spend a long time building the truck or do you want to drive it? I’d find a better shell and swap the parts over. 

[Eagle_SX4]

If I was tackling this project I would cut off the control arm mounting brackets and fix the frame first. Then decide if you want to switch to long arms or keep the stock setup. If you do long arms there are lots of good kits out there. If you want to keep it stock I would use this kit from Barnes4wd. It is out of stock right now but would be a great option.

 

https://barnes4wd.com/products/xj-front-chassis-replacement-brackets

 

[Pete M]

I'm a huge proponent of keeping the trucks on the road, but man, that's going to be some seriously invasive surgery.   I'm wondering how far the rot goes.  

[Tex06]

Honestly, not that bad. You already have a plasma cutter and MIG. Get a small cutoff tool (like 3" cutoff or a regular 4" grinder with cutoff wheels and a dremel for the nitty gritty stuff. 

Cut out areas that are more or less rectangular while the truck is on jack stands (take as much load off of that area before you start cutting).  Remove inner fenders and other stuff that may be in the way. Use cardboard (beer boxes work great!) and a sharpie and scissors to make templates for each piece you cut out. Doing it in bigger pieces is better, but I've patchworked several frames and unibodies (XJ and MJ) with good success. 

Make sure that where you're welding to is solid metal. If it's thin/rusty/iffy....it's gonna suck to weld to. Also, clean the area as best you can with a wire wheel before welding....clean steel is easy to weld to, dirty steel is not. 

 

Lastly, youtube is your friend. Look for "rusty frame repair" videos. You can weld in heavier metal to the thin unibody.  Lots of people have done this with good success. Good Luck!