Ultimate Rust / Undercarriage Thread (1 Viewer)

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Hey All, long time lurker here. I have really appreciate learning from everyone on this board, it's an amazing resource. I'm considering what appears to be a very well maintained truck (full dealer records for life of the truck, 1 owner), that runs very well and doesn't have an pressing needs. The mileage is around 250k and the price is reasonable. My only hesitation is the rust, which on this truck seems to follow an unexpected pattern. It's worse up front at the skid plate than anywhere else. And there's some scale on the frame, though it still seems solid. Any thoughts are appreciated.

Photos are generally of the worst affected areas.

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JustEthan said:
Additional photos. Also, there's no rust on the body.

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The cross member over the rear axle often gets mud in there and rusts out, take a look at that section where it meets the main frame rails. Also, the far rear cross member behind the bumper skin may also be a spot to check. You should also check out the rear brake lines where the run along the frame rail just behind the gas tank, another problem area. The rest of what's shown in your photos is not great but not terrible either. Clean it up with wire brushes and fluidfilm it .
 
To be honest, that's not that bad. Depending where you live check if anything is flaking or peeling. That looks like superficial rust to me. That skid plate is gone remove it and get an aluminum one if you live in a salt belt. My truck is worst then that, and I'm wire brushing/wire wheeling the frame and respraying it with a rust converter and then adding a few layers of rp-342 on top. These frames are actually incredibly durable. I'm going to see how long the frame on my truck lasts before it gives way.
 
I wanted to give you guys an update. I took it to local mechanic and he did everything for $600 bucks. Wire brush loose material then rust converter and lastly RP-342. I'm going to add another coat of the RP-342. I also bought the ASFIR skid plate aluminum is king in salt city. I also checked the integrity of the frame it's in good shape, anyone who lives on the salt belt if you know a good welder, just cut out the bad pieces and weld new plates. These trucks are solid.



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Figured to get some advice here as opposed to making a new thread.... I have a 100 series that has some rust. Its not terrible and I cleaned up the frame to get almost to zero except in the hard to reach spots. I'll probably end up spraying corroseal and then doing fluid film to to get those hard to reach spots (unless someone has a better idea).

My issue is the entire rear axle assembly. I am up in the air with what I want to do with it. Do I spend the time to remove it, blast it, and have it painted? Do I leave it on and clean it up the best I can on my own. Do I go the easy route and spray corroseal and then POR15 it? Or do I just say screw it and find one at a junkyard and replace the whole dang thing? Pictures below. Thanks in advance!
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Haha sadly, I can't it is mine. Just trying to decide the best way to deal with it. I don't mind spending a few days under the truck. It is just I also don't dismiss the idea of having someone blast it for me and then paint it.
 
TwistedCon said:
Figured to get some advice here as opposed to making a new thread.... I have a 100 series that has some rust. Its not terrible and I cleaned up the frame to get almost to zero except in the hard to reach spots. I'll probably end up spraying corroseal and then doing fluid film to to get those hard to reach spots (unless someone has a better idea).

My issue is the entire rear axle assembly. I am up in the air with what I want to do with it. Do I spend the time to remove it, blast it, and have it painted? Do I leave it on and clean it up the best I can on my own. Do I go the easy route and spray corroseal and then POR15 it? Or do I just say screw it and find one at a junkyard and replace the whole dang thing? Pictures below. Thanks in advance!
View attachment 3011911View attachment 3011916View attachment 3011917
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I would look more towards whats above that. Around the spare tire, rear cross member. Especially driver side, there is probably going to be a hole where it meets the frame. The axle assembly is pretty thick and you could probably mitigate most of the issues if its only there. Some of those things that bolt on to it might be a lost cause though.

You can replace that lateral control arm and its components for an easy way to make it look better. I'd be careful with those bolts for the sway bar bracket. Those miiiight break.
 
That spare tire carrier needs to be changed out, it looks more than a little worse for wear. I really have no idea what above it looks like. But the rear cross member looked fine last time I checked it. Just small surface rust around the holes which I already addressed. You can see what it looked like before I worked on it in some of the pictures.

I am a little bit cautious with the rear bumper. I only looked at it once when I had the PPI. It looked like those thing metal sheets (wings?) on the inside ends of the stock bumper were covered in surface rust. Plan on replacing it with a dissent bumper in the next year.

The rust on the car perplexed me. It was a southern car for all but 3 years of its life where it lived in Brooklyn NY. It appears it was parked on the street as only the rear part of the car had rust I was worried about. As if when the snow plow came through it pushed all the road salt and snow up under the rear. Everything else seemed appropriate for the age being around salt.

Definitely going to have things like brackets and the like break if I really start getting at it. One that looks like its at the end of the one is the one on the back off the diff cover (not sure what it is because can't see it in the photo maybe holder for break line). But plan on using a lot of PB blaster if I take stuff apart. Really leaning to just spending $800 bucks on finding one in decent shape and putting it in. Then doing an underbody spray by a professional shop.
 
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TwistedCon said:
That spare tire carrier needs to be changed out, it looks more than a little worse for wear. I really have no idea what above it looks like. But the rear cross member looked fine last time I checked it. Just small surface rust around the holes which I already addressed. You can see what it looked like before I worked on it in some of the pictures.

I am a little bit cautious with the rear bumper. I only looked at it once when I had the PPI. It looked like those thing metal sheets (wings?) on the inside ends of the stock bumper were covered in surface rust. Plan on replacing it with a dissent bumper in the next year.

The rust on the car perplexed me. It was a southern car for all but 3 years of its life where it lived in Brooklyn NY. It appears it was parked on the street as only the rear part of the car had rust I was worried about. As if when the snow plow came through it pushed all the road salt and snow up under the rear. Everything else seemed appropriate for the age being around salt.

Definitely going to have things like brackets and the like break if I really start getting at it. One that looks like its at the end of the one is the one on the back off the diff cover (not sure what it is because can't see it in the photo maybe holder for break line). But plan on using a lot of PB blaster if I take stuff apart. Really leaning to just spending $800 bucks on finding one in decent shape and putting it in. Then doing an underbody spray by a professional shop.
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The reason why the rear always goes first on these trucks is by poor design. The rear brackets and bumper reinforcement is in the open, the salt water just splashes right in that pocket during the snow days and in my opinion doesn't drain properly. Spare tire carrier is also an issue there, I'm going to change mine to just be on the safe side, I have seen people retrofit a vinyl cover to protect the rim. Overall, this looks superficial to me and your brake lines look clean compared to mine, a good wire wheel to loosen up some rust flakes and hit it with primer and paint.
 
TwistedCon said:
Figured to get some advice here as opposed to making a new thread.... I have a 100 series that has some rust. Its not terrible and I cleaned up the frame to get almost to zero except in the hard to reach spots. I'll probably end up spraying corroseal and then doing fluid film to to get those hard to reach spots (unless someone has a better idea).

My issue is the entire rear axle assembly. I am up in the air with what I want to do with it. Do I spend the time to remove it, blast it, and have it painted? Do I leave it on and clean it up the best I can on my own. Do I go the easy route and spray corroseal and then POR15 it? Or do I just say screw it and find one at a junkyard and replace the whole dang thing? Pictures below. Thanks in advance!
View attachment 3011911View attachment 3011916View attachment 3011917
Click to expand...
Never use POR15! It's only a plastic cover coating that peels off in time. If you can use a compressor and needle gun, follow with a power tool with hard wire brush attachment. Blow off all debris/dust and add several coats of a reputable Rust Reformer then before winter coat everything with Blaster Surface Shield.
 
Quick question, anyone know where I can buy an extension/spray wand that fit onto the Amazon Cosmoline spray can? The transparent tube that I have only fit the Fluid Film can. Thanks!!
 
The body is weak, the courage is strong.

Salt on roads should be illegal.
 
Devils Paw 80 said:
It looks fine except for that rusty area. What happened?
Would not pay $12K for it, but then I'm a cheapskate.
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I'm not entirely sure, but my speculation is that in the first 4 years of its life that it spent in MA , salt got behind the floor pan cross member and rusted it out from the inside.
 
Good thing that isn't structural. Have it cut out and patched correctly. 12k? maybe if the interior is in excellent shape, timing belt has been redone and everything works (ac, sensors, windows, all seat and steering column adjusters, etc.)
 
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