Have they fixed you recalled frame issues? My vote it to replace the differential instead of repairing. Toyota should step up to the plate on this one.
It looks to me like you need an entire rear axel including the pumpkin. The third member and the axel shafts are probably ok, since they are on the inside.
There’s some possibility the only thing that is leaking is the front seal, and the wind is moving the oil around. Unlikely, but possible. You could try replacing that front seal or there may be more than one seal. I removed the entire third member and the axel shafts from my Ford truck one time, and it wasn’t that big of a job. Well, maybe I should say it wasn’t a super-big job. Putting the third member back in though, that was a big job. It’s slippery and heavy. Get some help if you try this on your own. A shop would be the better way, first you wouldn’t have to do it, and second, they could do it on a lift which would make it much easier.
I see a stamped sheet metal rear differential cover pressed into the cast iron axle. But that’s just me.
The casting is leaking, because it’s rusted out
Due to road salt used
Due to it being a Toyota truck
Not because some error was made when the rear end got put together
Sorry, buddy . . . I’m not buying into the whole casting error thing
Ain’t gonna happen
No way
No how
What is the third member and do all rear ends have it?
These pictures will explain it far better than I can
Essentially, the “guts” of the rear end
https://www.google.com/search?q=third+member+pictures&tbm=isch&imgil=8ox9q3SrRYi_BM%3A%3Bhttps%3A%2F%2Fencrypted-tbn1.gstatic.com%2Fimages%3Fq%3Dtbn%3AANd9GcQDUGEqLAXNvRfLVx_wY2fsMosmSmk599-f7wFpbQ3GmsDhIOGv%3B400%3B273%3B5zbxVYhJOv-l1M%3Bhttp%253A%252F%252Fwww.metropartsmarket.com%252Frearend%252Fproducts.html&source=iu&usg=__iyM1TysqYt8xD8UdB0aXbjwSXGY%3D&sa=X&ei=MjW2U4TINtGIogSx6YD4Bw&ved=0CCcQ9QEwBA&biw=1242&bih=585#facrc=&imgdii=&imgrc=8ox9q3SrRYi_BM%253A%3B5zbxVYhJOv-l1M%3Bhttp%253A%252F%252Fwww.metropartsmarket.com%252Frearend%252Fproduct_1.jpg%3Bhttp%253A%252F%252Fwww.metropartsmarket.com%252Frearend%252Fproducts.html%3B400%3B273
In some rear end designs, the center section is indeed a casting into which the axle tubes are welded in place. But this Toyota design, with a removable pumpkin, the housing looks like it was formed by welding up steel stampings…The back cover is stamped out of steel sheet, formed in a press and welded in place…The pumpkin is a casting but not the housing…
Hey M.B., my 1990 model, a 4 speed, is carbureted…That year about 70% were injected and 30% still carbureted…
Caddyman is correct, the top and bottom halves of the axle housing are stamped steel as well as the rear cover. I have replaced one. The only cast part is the differential (third member) housing.
@db4690 thanks. I’m pretty sure my 50 caddy rear end is built that way. And I’m guessing the old ford 9" as well. I’m used to the modern ford 8.8" with the removable cover
@Fender1325
Yes, the old trusty Ford 9" is built the same way
First member: Engine
Second member: Transmission
Third member: Differential
I hope we don’t get into another drawn out argument on the third member reference. I still remember the last one…
Drain it. Wire wheel the housing cover until you find the pin hole(s). Clean. Clean again 
Fabricate a small steel patch from sheet stock. Braze it over the hole(s). Refill. This will last until another hole appears, if one ever does.
The epoxy patches will buy some time but are likely to fail eventually- sooner if the metal is not pristine clean before applying. Even empty, it will be weeping out the hole enough to poison the area…
I think we will get into another drawn out argument
Because we don’t agree as to the cause of the third member rusting out
The opposing sides have stated their case and aren’t budging and won’t let their opinions be changed
And each side knows they’re right
So be it
I have seen porous castings before. In fact, the most amazing instance was a brand new Grand Marquis my father bought and was soon dripping on the garage floor. The transmission housing had a casting fault. The dealership was authorized by Ford to remove the guts and transfer them to another housing! I was astounded that was more economical than a swap. I was also quite concerned that more could go wrong with this approach but they did the deed and it never leaked or failed again in any way.
That being said, this is a stamped steel cover welded to the housing…
Today, much rolled steel, hot or cold, is made from scrap…If the finished product has “inclusions”, impurities which go undetected, the final product is prone to rust-through which is sometimes blamed on paint failure…While manufacturers take great care to properly finish the exposed body-panels, underneath and in other hidden areas they are not so fussy…Small changes in the steel alloys used can make a big difference in corrosion resistance…Take a look at recently installed guard rails…Most are no longer galvanized or painted. They are installed unprotected and quickly develop a coating of fine, uniform rust that resists further corrosion and they hold up as well as anything else…
Some steel is made to rust and not need paint: I see it mainly on bridges. Kinda ugly.
I’m surprised that sheer torque hasn’t twisted that rusted differential housing into pieces and wonder how bad the rust on the rest of the truck is.
It’s certainly not something I would feel confident with on the road many miles from home.
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