02 4runner rear diff rusting out!

looked under my 4runnr yesterday and saw oil seeing al over my rear diff. Crawled under to see what was up. Def a lot of rust there but really didn’t think it was at all possible to rot through. I thought for sure it had to be coming from somewhere else but there are not any deals back there. I can’t believe it. Have no idea what to do. Rest of the vehicle is in good shape. New t. Belt a year ago. 175000 miles. My 89 yota pickup has 210000 and has hardly any rust

 

Maybe the seals are just leaky? Clean it up really good and check it again in a few days, see where it’s coming from, as well as check the fluid level. You can always take a wire brush to clean up the rust, use some rust reformer, then spray paint to protect from more rust. If it’s rusted through you should be able to spot the problem area pretty quickly.

 

Thanks. Super frustrating. I will try and clean it up more. Just not sure what deal would be leaking as the entire front of diff is clean. Checked level and it was only down 1/4 q. My rear backer plates are rotting out too. Trying to figure out what would be more cost effective. I don’t think I can find a good used rear axle up here in AK.

 

Do you have any pics?

 

3rd Gen 4runners rust like crazy, even if taken care of, very normal.

Check the diff breather to make sure it spins.

 

I will try to get a pick.

 

Funny there was a recall on the Tacoma frames but nothing on the 3rd gen 4runner. Do we know if they have beefed up there diff housings? I have a little surface rust on my new Tacoma drive shaft. Should this be cause for concern. I’m now paranoid. Thanks for the help.

 

Given your location, I would immediately try to clean the underside of your truck, use rust reformer and then spray paint a day or two later any rust spots. Then fluid film the underside heavily or take it somewhere like Krown for treatment. This will help prevent rust, as you are in a very snowy area. I’d treat it at least twice a year. Stay on top of anything that even looks like rust and hopefully make your new truck last a long time.

 

I def. am going to go the fluid film route. Did I here somewhere that this stuff can potentially shorten the life of the coating on our new frames. I thought I read that but maybe not. I could be confusing it. I will try to post a pic of the rust spots on the new truck. Only has 5000 on it and am not sure I should be seeing any of it. Thanks for the follow up!

 

I’ve not heard anything about fluid film shortening the life of frames.....besides their version of rust resistance leaves much to be desired.....I’ll take my chances with FF. I had some early rust on uncoated suspension knuckles and such on the Tacoma I had, as well as my 4runner and I treated them like I described above except I used oil based paint and used a foam brush to apply. I FF’d the underside of both vehicles and as soon as I get a chance, I need to do my runner again too. I plan on keeping my runner for 30 years, so I don’t want it to rust away on me!

 

Rodger the 30 years. I planned on keeping my runner for at least another 10. Runs and shifts great. But man I need to catch up on the rust. Thanks for the advice

 

My '01 Tacoma had a new frame put on a couple years ago, solving a lot of its rust issues.... except for the rear end. I'm concerned my axle housing is going to start leaking so I'm going to wire wheel the rust down, spray some rust converter, put some POR15 down and then keep up on applying Fluid Film. I tried FF this winter and I think it works great. The inside of my frame is still nice and wet from it when I applied it last fall.

My backing plates also rusted through like yours, so I'm replacing those too. Going to be quite the chore.

 

I put por15 on my sliders. I’m going to wire wheel my diff housing tomorrow and see if I can tell where it’s leaking. How do I know if my breather valve is working?

 

Well. I spent half the day under the runner today going at it with a scraper and a wire wheel. Got the whole thing cleaned up real nice... absolutely no leaks! My guess is that maybe the fill plug crush washer was bad or leaking and was being sucked up by all the rust? Pulled plug the other day and put 1/4 qt. Oil in with new crush washer. It was still weepy after this but was before I had cleaned it all up so I’m guessing the first time I washed it down it still had oil soaked up in the chunks of rust. I really don’t know any other explanation to this as my diff is now very clean and bone dry. I am taking this as a good learning lesson in rust and prevention. I will now be very meticulous in the future. Especially with my new Taco.