Rear Diff Rust

Wondering if anyone has advice regarding rust on my rear differential. I bought this tundra back in August and knew that this was going to be a weak point for it (it already has a new frame) and I'm wondering if I should do anything about it before winter hits. I live in NJ, so road salt is aplenty, but I'm not sure if at this point it may be better to leave until Spring and hose it off after I drive over salt.

Is it worth sanding down and painting now? It doesn't seem like it is leaking yet, and the guy that I got it from took great care of it. I'm a newbie when it comes to truck maintenance, so any advice would be great.

 

I’d sand and scrape those chunks off and then squirt some penetrator or oil all over those rusted areas. Follow up with a grease rub afterwards or sometime in the spring.

We’ve seen some gnarly rear diffs on some members here and they tend to rust through and develop pinhole leaks. Most end up doing various combos of new covers, epoxy, and/or POR15 paint.

Yours is borderline almost a problem.

 

Wow that looks bad.

 

I appreciate the advice, I'm thinking about trying to sand it down a bit tomorrow, any specific penetrating oils you think would be good?

 

I’d use motor oil and rub it on with a sponge. PB Penetrant works, too but doesn’t last like oil. The Grease Rub is best but takes time. I’d use a pump spray bottle and fill it with oil and squirt it everywhere on the frame including up into the box frame. Lay some plastic or covers down to catch the run off.

 

That needs a wire brush or better wire wheel to save your arms. Then a heavy coat of grease. I would be worried how much longer some of those spots will go without needing replacement.

 

Would the oil ever effect painting and sealing it down the line? Luckily the frame is in really nice shape, but I'm sure it wouldn't hurt to spray it down anyway.

 

How much you think a replacement would run? I'm looking to hold onto this thing for a while, and this seems to be the only major trouble spot. I'm not really afraid of putting in some money, provided it isn't completely obscene.

 

Might be able to find a salvage rear end from somewhere out of the rust belt. Not sure of cost

 

I wouldn’t bother painting anything unless you plan on doing the rear diff cover replace then I’d hold off in that area until that was finished. I’d oil and grease the crap out of everything asap. Better than paint and cheaper/easier. Oil/Grease penetrates. Paint only lays up.

After, your stuff will look black again kinda like around your diff plug. No rust there on the black oiled soaked areas.

 

I've looked around for a bit and finding a salvaged one seems like it's what people tend to do... Only problem is I have no idea how to find one

 

Knock the rust off and post pics tomorrow before oiling/greasing. Sometimes the rust scale makes things look worse. Doesn’t look leaky for now which is good.

 

Welcome to the club..
I wouldn't go so far as to replace the entire differential. Mine had similar rust on it, and I cleaned the entire rear axle up with a wire wheel, and then painted it. The majority of the axle is fairly thick cast steel, so you can be aggressive with the wire wheel. The only thin area is the differential cover. If you find Pin holes in the bottom of the rear cover AFTER wire wheel cleaning, drain the diff and Spread a layer of Black Form A Gasket over the pin hole areas, followed by a coat of POR-15 or Chassis Saver (my paint of choice) over the diff cover. Then you can spread grease over the entire axle assembly for protection.


.02

 

This^^^

 

I appreciate the advice, and I'm probably gonna do something just like this, it's seems like it's the best option. However, I'm just a little worried about sanding down close to bare metal so close to the time of roads being salted, I wouldn't want to mess up and then risk exposing more of the structure to potentially rust... Would it still be worth it?

 

Absolutely it would be worth it. Even if you got under there with grease and did nothing else, it would help preserve the surfaces until the spring.

 

Clean it up and inspect tomorrow. Buy a tub (not tube) of MolyB and slather it up if all looks well. That will stop the rust in its tracks. Might not need to do any repairs at all. Worst case is you protect the truck until spring and then do repairs. As long as its not leaking you should be good. Most bad rust diffs only leak slowly at first so you’ll have time anyways.

 

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I'll get armed with some wire brushes and grease and update you guys once I clean it up. Hopefully it'll be tomorrow, if not it should be early this week. Thank you for the help!

 

car-part.com or other members.

If you want to DIY it, call/search your local junkyards. Probably best to find one outside the rust belt though.

 

When I treated rust on my diff (and frame), I scraped and wire brushed everything really well, so as to get everything loose off, but not to bare metal, then I sprayed it with ‘rust converter’ to try and take care of any remaining rust I may have missed, then I painted it all (black), then I sprayed undercoating over it all, then I coated it with ‘rust protectant’ (like wool wax).
I’m not sure what the consensus is on using ‘rust converter’, and some people don’t like undercoating, but I’m happy with the result, and just plan on keeping up with the ‘rust protectant’.
If it’s getting cold and/or wet where you are, stick a heater underneath while anything paint like is drying.

 

The only part you need to worry about rusting through is the cover. As someone else mentioned the rest of the axle is heavy cast.

Scrape off the scale, paint if you want, then oil it.

If the cover is significantly rusted through Dorman and Barnes 4x4 make replacement covers. The old cover will need to be cut off and the new welded on.

 

Don't apply grease or spray fluids now if you ever intend on painting it (and I recommend painting it).
Remove the rust you can, then treat the diff cover with Ospho (phosphoric acid) which will convert the remaining rust to a sealed, paintable black surface. Then paint with your paint of choice, then apply your grease/spray/ect. coating of choice. If you grease/spray now before paint, you'll never get paint to stick unless you go down to bare metal -- which you probably don't have much of on that diff cover.

 

So, what I ended up doing today:

I brushed the whole assembly down with a wire brush, not to bare metal, but just enough to get the scale off. It seemed solid, no signs of any leakage.

I decided to follow it up with a thick coating of fluid film. I had some on hand already, so I figured no harm using it up. I'm pretty confident in the result, and it's really all I can get done for now anyway, and my bet is that the road salt starts tomorrow.

I actually scaped and fluid filmed quite a bit of the rear end while I was under there, got the bumper and frame as well. I've read nothing but good things about the stuff, maybe I'll update throughout the winter on how it's holding up.

 

Get this: https://www.barnes4wd.com/Differential-Covers_c_44.html

My 06 started getting pinholes and leaking. I ordered this and had my mechanic install it. It was a bit pricey but it has a larger capacity and is way thicker metal than the stock one. It is some work to put on. The differential has to come out, old cover gets cut off, new cover welded on, etc.

 

I did mine about a month ago getting prepared for winter. It looks bad, but once you start cleaning it up, it’s actually okay. It’s not great. But it took me about 3 hours to do, I used a wire brush to get most of it off then hand sanded with abrasive cloth to clean up hard to get areas. I didn’t do anything special, just wanting to make it through winter into next spring when I have more money and time. I would spray some alcohol on it and let it dry before painting to help the paint stick. Would not recommend oil if you plan on painting. Hope everything works out.

 

I got my replacement from LMQ they delivered free to the shop I had do the work. Since then I've done the Por15, oil spray routine. Grease is a good idea or thickest oil you can get.

 

I think I'd try a mineral based solvent rather than an alcohol based material

 

same with me. it's a great product.