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How long will rusty TJ frame last?


Jeb

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I just bought a 99 Sport, 4.0. This is my first Jeep and I researched as much as I could about purchasing. Seems like other than basic mechanical function, frame is the most important. It’s got rust all over, fairly heavy flaking in many spots, but I couldn’t find a hole anywhere. I punched as many suspect spots as possible but didn’t hit anything with hammer or screwdriver. How long will a frame in this condition last if I do nothing? I will likely just use it to cruise around, possibly some light trails, I will not add mods or rock crawl. Note: it was purchased in Minnesota and has been here its whole life. First time posting, first day on the forum, first week of Jeep ownership. Thanks for any honest input you can give.
 
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Jeb

Jeb

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Thank you - I’ll take some pics next time I can stand the brutal humidity in the garage for a few minutes!
 
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Jeb

Jeb

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Let me know if this tells you anything. Starting with front passenger and going clockwise around vehicle:

63AB882E-D2D7-4927-9F19-98AC7B62ADA3.jpeg


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9B7F32AE-E5DF-4CE6-8CCB-A4B3F55F41A1.jpeg
 

bromel

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Skid plate? That is usually the first point of failure. The nuts pull out of the frame and the plate hangs loose from one end.
 
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Jeb

Jeb

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I’ll double check, but I think it’s still intact. Rusty like everything else, but not hanging.
 

madcanvis

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Skid plate? That is usually the first point of failure. The nuts pull out of the frame and the plate hangs loose from one end.
⬆ This.

I was the unsuspecting buyer in my situation. All other suspect points were/are good. However, after 4 months the DS front bolt was hanging 1/2 inch. 1 month later it was time to call up SafeTCap.
 
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Jeb

Jeb

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The older gentleman I bought it from used it fairly regularly for fishing, and took it in for regular maintenance, said whenever his mechanic told him something was busted, he had it fixed. So it would be a fluke if it suddenly fell apart, but in just wondering if I have more like a year or two, or five years. How much do safeTCaps cost? I’ve seen different pricing. I’d have to have someone install it.
 

bromel

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Look, would I have bought that Jeep? No. But you have it now, so here we are. Send more pics of the skid plate when you can. Assuming it's not about to pull out, you'll probably get a few years out of the frame—that's if you drill drain holes and flush all the crap out inside. I would douse the inside with fluid film and hope that it slows the rust. These frames rust from the inside out, so it almost certainly looks worse on the inside. Then I'd POR-15 the outside and keep your fingers crossed.

Yes, Safe T Caps could fix that frame, but you're looking at minimum $2k to install them, depending on where you go. How is the rest of the tub? Those torque boxes don't look great. You don't want to invest in caps if the rest of the Jeep is falling apart.
 
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Jeb

Jeb

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Thanks for the honesty - I’ll check out the skid plate when I get a chance and post pics. I bought this just to have access to a Wrangler, and paid low blue book. Interior is almost flawless, tires are good, 4.0 and tranny are excellent, 92k on them. So if I can manage the poor frame for let’s say 2-3 years maybe then I’d sell it and drop more $$ for something newer with a cleaner frame.
 

jodomcfrodo

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I wouldn't be surprised if you could put a screwdriver through that frame somewhere. Unless you have holes, it should be generally OK to drive confidently. But you have to try to make those holes first. SafetyCaps would probably be a good solution for you whether you want to get out of it in two years or not. Even if the frame lasts two to three more years, you will get pennies on the dollar of what you paid trying to sell it with an unsafe frame.
 
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Jeb

Jeb

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Definitely wouldn’t sell it to someone who didn’t know if the frame were deemed unsafe by a mechanic. Thanks for the feedback, everyone. See pics of skid plate - I tried pulling on it, pounding it, stabbing rusty areas with a driver - nothing happened. I don’t know the best screwdriver method but I stabbed the crap out of the rustiest areas on the frame and it didn’t really make a dent. Felt and sounded like I was hitting a steel beam with a screwdriver. I don’t mind making a project out of stuff like suspension, axles, etc, but I’d rather not do any frame-off work myself.

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A5003DCA-E7B2-46C5-B8DA-A88D640AC659.jpeg
 

jodomcfrodo

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Definitely wouldn’t sell it to someone who didn’t know if the frame were deemed unsafe by a mechanic. Thanks for the feedback, everyone. See pics of skid plate - I tried pulling on it, pounding it, stabbing rusty areas with a driver - nothing happened. I don’t know the best screwdriver method but I stabbed the crap out of the rustiest areas on the frame and it didn’t really make a dent. Felt and sounded like I was hitting a steel beam with a screwdriver. I don’t mind making a project out of stuff like suspension, axles, etc, but I’d rather not do any frame-off work myself.

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The area where the frame meets the skid plate is a problem area for rust. Remove the skid plate, being careful to support the transfer case or transmission with a jack. Then put a screwdriver on the bottom of the frame where the skid would go and hit the screwdriver with a hammer. If that causes no issues, you should be ok for a while. Though, it is just a matter of time.

If you stick a finger in one of the holes of the frame, what do you feel resting inside?
 

Joseph

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My Jeep was kind of like yours. I’ve had 4 caps installed on my frame, two of them almost two years old. They look great and will hold well as long as the welder doing it knew what he was doing.

Understand that you’ll have to get those done if not now in the next year or two. Probably not all at once, but I would do it before it gets worse.

Also, not only do you have to worry about frame rust, but axle rust too. Those are easily replaceable, or can be welded. I’ve had my front two lower control arms and passenger spring perch/track bar mount replaced.
 
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Jeb

Jeb

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I sprayed out the frame where I could the other day. And there are definitely plenty of flakes in there. It needs to be thoroughly cleaned out for sure. I have heard about taking the skid plate off and supporting Like you said. Kind of a newbie question, but where exactly should I put that Jack? Then just unbolt the skid and it comes right off?
 
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Jeb

Jeb

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If you don’t mind my asking, were the caps about two grand like was mentioned above? I would be willing to drop two grand if I were fairly certain those would hold for several years. It would be cool to work on this jeep with my son, so like I said, almost anything that isn’t the frame I don’t mind messing with and replacing myself. I just need the frame to be safe. I have an arc welder, but I guess since I haven’t used it in two years, I’m not going to be using it.
 

bromel

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I'm going to play devil's advocate here and say not to remove the skid plate. I think we should assume much of the frame is rotted away underneath having seen those pictures. Removing the bolts might break free the nutserts. At this point I think you want to milk as much as you can out of this frame before determining whether to do a safe t cap job.
 

bromel

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If you don’t mind my asking, were the caps about two grand like was mentioned above? I would be willing to drop two grand if I were fairly certain those would hold for several years. It would be cool to work on this jeep with my son, so like I said, almost anything that isn’t the frame I don’t mind messing with and replacing myself. I just need the frame to be safe. I have an arc welder, but I guess since I haven’t used it in two years, I’m not going to be using it.
The actual cost for the two caps is around $900 I think, from Auto Rust Technicians. (https://www.autorust.com/product-category/jeep/jeep-tj/) You'll want the full-length caps almost certainly as you likely have rot near the rear control arms. You can also get caps from Pocono Metal Craft, and they're a bit cheaper, but I can't speak if the quality is comparable. If installed right (i.e. cutting out ALL of the existing rust), they will outlive the rest of the Jeep. The reason the frame rotted out is because the factory did not include drain holes, so water and salt pooled inside over years and years. The caps do come with a drain hole, so you should be set.
 
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jodomcfrodo

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I sprayed out the frame where I could the other day. And there are definitely plenty of flakes in there. It needs to be thoroughly cleaned out for sure. I have heard about taking the skid plate off and supporting Like you said. Kind of a newbie question, but where exactly should I put that Jack? Then just unbolt the skid and it comes right off?
It should go anywhere where you can get it before removing the skid. The transmission is typically the easiest place to put it. The skid in the center also acts at the transmission mount, so if you don't support the transmission, the entire driveline will weigh on your engine mounts as it tries to leverage the motor. Things can rotate around the axis of the motor mounts, but only so much.

You need to remove the 6 bolts holding the skid to the frame as well as the 4 holding the transmission mount to the skid plate. Then the skid should come off.


I'm going to play devil's advocate here and say not to remove the skid plate. I think we should assume much of the frame is rotted away underneath having seen those pictures. Removing the bolts might break free the nutserts. At this point I think you want to milk as much as you can out of this frame before determining whether to do a safe t cap job.
If you are not able to remove the skid plate, the Jeep is not safe to drive. Either you decide to not remove the skid plate and immediately patch the frame or you remove the skid plate to check for rot. You can't drive a rusty TJ frame around the road blind to how rusty it is. Better to know your frame is falling apart than to have it happen on the highway.
 
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