As like many of you my 4 runner Is also leaking from the Rr. Diff. housing. I called customer service and they pretty much told me that my vehicle was out of warranty and there wasn't any recalls on the vehicle for my problem there wasn't anything they could do. So Not willing to stop there I got a call into the Executive office of Toyota in Torrance California, office of the CEO of toyota America Division, The operator was not willing to let a customer talk to the Ceo, but she did put me through to an executive analyst to the ceo, so I explained my problem in detail to her, Through a series of conversations back and fourth she arrainged for me to have my 4 runner brought in to the dealership for a thourough inspection of the vehicle to see if there was anything toyota could do for my vehicle issue. Upon receiving the fax of the inspection report she contacted me today to discuss its findings.
The findings read as follows, Inspected housing,found fluid leaking from housing from front yoke through rear cover; Metal Porus and thin- recommend replacement of housing and associated Hardware repair estimate $1491.28 + tax.
They also found Exhaust leak from center pipe (catalytic converter) Recomended replacement $1495.06 + tax and several other small issues at a cost of $138.70 + tax.
Last but May be even a bigger problem under the comment section of the report the technician hand written , FRAME IS BAD, RUST PERFERATION , And I believe (sloppy writting) it said Right rear Rail. Now thats toyotas words not mine.
So the Executive analyst Told me What Customer service said initailly that there was nothing they could do because it was out of warranty and there were no recalls. She also said that possibly some day there could be some sort of recall but she cannot make those determinations. If there were enough complaints It may compell Toyota to take some sort of action. I'm guessing that she wanted to have the vehicle inspected more for toyotas interests and not my best interest since I received the same generic answer again.

The next step Is to File a complaint with the ( NHTSA ) National Highway traffic safety admin. on line to log my complaint and hopefully all of you will do the same, The more complaints filed increases the chances for Toyota to take responsibility For the excessive rust and inferior metal used on all of the vehicles in question.

 

I also have suffered with the rear diff rust. Patched with epoxy. LAst year when my 99 4Runner was in the shop to repair a brake line leak they told me that the frame was rusting through. Now I have rust holes right through the rocker panels below the doors. Truck has 195,000 miles, but the engine and everything else is still in pretty good condition.
I have filed a complaint with the NHTSA about the rear diff.
Toyota has replaced the frames on a huge number of Tundras under recall.

 

Hi I've been on this site a ton and its high time I posted something. I too had the rear axle housing rust problem - it appears to be a result of the welds that hold the metal clips for the parking brake cable - or at least that is where the rust appears to have started. If memory serves me, Toyota dealership quoted me $1400 to replace the axle (I so wish the cover was just bolted on and I could just replace it). My 1998 4runner had 200k miles on it and I wasn't eager to drop $1400 for an axle. Looking for a junk yard replacement seemed to be a daunting prospect give the wide variety of axles. I had oil weeping from the housing - I would get a drip or two on the floor every week or so. My local mechanic suggested permatex - I put that on about a year ago and it held up pretty good, but I noticed a few drips again a few weeks ago and upon inspection the permatex seems to have degraded a bit.

Having whacked up my fiberglass boat once or twice, I knew that Marine-Tex is just an awesome product - so a couple days ago I cleaned up the housing and applied black marine-tex (its usually white but I purchased the black variety, bought it from a marine supply store - 14 bucks). I haven't used JB Weld but its probably a very similar product.

So it appears to have done the job and I hope to get several more years out of it. I also filed a complaint with the NTSB and I would encourage others to do the same.

I attached a pic - I hope you can make it out. I'm really pleased with the results and I believe the Marine-Tex will hold up indefinitely.

 

Hi I've been on this site a ton and its high time I posted something. I too had the rear axle housing rust problem - it appears to be a result of the welds that hold the metal clips for the parking brake cable - or at least that is where the rust appears to have started. If memory serves me, Toyota dealership quoted me $1400 to replace the axle (I so wish the cover was just bolted on and I could just replace it). My 1998 4runner had 200k miles on it and I wasn't eager to drop $1400 for an axle. Looking for a junk yard replacement seemed to be a daunting prospect give the wide variety of axles. I had oil weeping from the housing - I would get a drip or two on the floor every week or so. My local mechanic suggested permatex - I put that on about a year ago and it held up pretty good, but I noticed a few drips again a few weeks ago and upon inspection the permatex seems to have degraded a bit.

Having whacked up my fiberglass boat once or twice, I knew that Marine-Tex is just an awesome product - so a couple days ago I cleaned up the housing and applied black marine-tex (its usually white but I purchased the black variety, bought it from a marine supply store - 14 bucks). I haven't used JB Weld but its probably a very similar product.

So it appears to have done the job and I hope to get several more years out of it. I also filed a complaint with the NTSB and I would encourage others to do the same.

I attached a pic - I hope you can make it out. I'm really pleased with the results and I believe the Marine-Tex will hold up indefinitely.

Btw, I've also had good success in stopping further undercarriage rust with several cans of Fluid Film. Boeshield is also really good, but the Fluid Film is cheaper.

 

Yes, i also have a rust problem with my 2002 4runner. It goes in the shop tomorrow.
I might have to bite the bullet and by a junk yard differential if i can find.
Just surprised how widespread this problem is!

 

good luck Starlifter. I had some wobbly-knocky noises coming from my rear differential and my mechanic said it needed to be replaced. The rear axles seals were also leaking and referred me to a transmission shop which apparently had the large size machine press required for the axle seal job ( he did not have a press large enough). Transmission shop guy found a used differential at a local junk yard (low mileage, so I'm told) but the whole job was still $1700. I thought that was a steep but not much I could do about it. That was 2 years ago - been running fine since. Oh and that Marine-Tex epoxy I used to cover the pitted area on my differential failed about 6 months later. Sorry I should have posted this info sooner. I'll tell you what is working like a charm for several years now - Fuel Tank Repair Epoxy. Hardens up in about 60 seconds, so you gotta work quick. I used two packages - cost about 15 bucks and it solved me problem.

 

Had to replace bearings on rear axle of my 99 4runner a few weeks ago.
Mechanic said it was the toughest thing he had ever done.
The seals had been leaking prior to that.
Took me 2 years and 3 mechanics to diagnose the noise coming from the rumbling bearings.

 

Hi, just wanted to add my situation to the thread.

I have a 2001 4runner limited, and as you'll see in the pictures, its also very rusted. my differential oil started seeping through the rust. i ended up fixing this by using eastwood chemicals rust encapsulator. i used their chassis clean to clean off any excess oil, then wire brushed all the rust on the entire car. the rust encapsulator is fortified with epoxy which helps seal it in. since i had access to a lift (work at a shop) i coated my entire frame with this stuff. there is now not one spot of rust to be seen!

And a big thanks to the poster who recommended giving attention to the breather. mine was completely gunked shut. some compressed air and some wd-40 cleaned it right up and i was able to save getting a new breather.

 

Just wondering if this is still an issue or something that Toyota is still avoiding? We are in the market for a 4runner but this problem is concerning. I like to have the repair manual so I can do a lot of work myself but this seems to be a pretty expensive & complex issue.