Front diff going bad on a road trip -should I fix ASAP?

If you separate the half shaft from the stub shaft, and leave the stub shaft in the diff, it shouldn't leak. You will get grease everywhere (unless you clean the tulip cup on the stub shaft well), but it shouldn't cause an issue with the diff itself.

You would run into a problem on the outboard side I believe. AFAIK the wheel bearing is retained by the splined shaft on the outboard side of the CV joint and the 35 mm nut that threads onto that shaft, through the hub.

IIRC, if you had pre-runner hubs on hand, you could then leave the stub shaft in the diff, pull the rest of the CV axle (e.g. the half shaft, the CV joint) as a single assembly and then replace the 4x4 hub with a Pre-Runner hub and still have everything retained correctly.

 

The needle bearing on my 09 allowed the drivers side CV end going into the front diff to have lots of play for the last 80k+ miles and I finally got around to doing the ECGS bushing, seals, and Napa CV axles.
On pulling the needle bearing out it looked fine no damage but after the ECGS bushing was installed that CV now has no/very limited play just like the pass side and front end is smoother.
Do not base an immediate requirement to replace that needle bearing "on lots of play" only.
As others said could be front wheel bearing or did you ever check the front diff gear oil level?
Other noise areas are the idler and tensioner pulleys, PS, Alt, AC compressor, fan belt. 2012 so after 10 years and probably at least 100k miles could be driveshaft related also. You need to drill down to the real cause/area.

 

If the sound goes a way in 4WD it’s probably the needle bearing.


This is a video BEFORE I replaced the needle bearing.
I was replacing my wheel bearing because it was roaring.
My vibes got substantial softer in 4WD, so that why I replace the needle bearing too. (Nock it all out at once) I drove on it for about 1 year before I replaced both. (10k miles or so)

Even after the ECGS bushing, I still play. Maybe 1/3 to 1/2 less?
But there’s still play.
The vibration is gone. So that’s good.
Whether the bushing or the wheel bearing fixed the vibration, I don’t know?
Maybe a combination of the 2.

FWIW, my growling noise never went away. It just got quieter or louder depending on the direction I was turning.

Link to my “Process of installation”.
https://www.tacomaworld.com/threads/ecgs-install-advice.712573/

https://youtu.be/4MMt-AB0fvE

 

Sounds like a wheel bearing

Lift the front wheels off the ground and spin each one by hand while holding the knuckle. If the bearing is bad it will feel rough through your hand on the knuckle. Any roughness at all is bad, it should be quiet and smooth. Compare side to side.

 

That’s the best way I’ve found to diagnose them on the Tacoma.
Grabbing at 9 and 3 and shaking resulted in nothing for me.
I don’t know why, but both of mine showed No play. But could clearly be heard (in cab) and felt at the knuckle.

 

Just to update - the truck has made it home. Once I got everything apart it appears to be the wheel bearing - the left side is definitely rougher to turn than the right. It wasn't obvious until I removed the brake calipers. I have the bearing hub assemblies removed from the knuckle now and it's pretty apparent. I just pm'd 05Taco4x4 for a set of new parts!

 

you could always pull the axles and put some flexseal tape over the diff holes

 

Never mind the CV axles, they beat everything out of their way within a few miles.

 

So... I have parts on order but have been having trouble finding the one seal 90316-A0001. Now the dealer I ordered from is saying it is backordered 3 weeks. And it's seeming like all the toyota outlets are the same. Any reputable sources on Amazon or eBay? Or aftermarket substitutes?

 

If that’s the one that goes over the CV, I opted to not change it.
I just replaced the one on the back side of the knuckle. Mine looked good and I just plain didn’t want to “figure out” how to change that seal with the axle still in the truck.

If it’s the one for the the back side of the spindle, Advanced Auto had them in stock here.
You might check there. They were about $25 each if remember. Made by National

 

I dunno about 2nd gens but on a 1st gen this is a huge no-no...the CV axle/axle nut holds the wheel bearing together and without it you won't get more than a few feet down the road before you suddenly have a much bigger problem on your hands. I would suspect its the same with the 2nd gen 4x4s.

I sorta learned this the hard way after cross threading the axle nut before going on a road trip, decided to deal with it next time...well...next time happened to come about 300 miles later and cost me a new wheel bearing as well.

if you had to, flex seal over the diff (be surprised if that holds lol) and cut the end of the cv axle that goes into the hub and make sure to torque the axle nut onto it.

 

It’s the same. You’d have to keep the stub shaft in the hub assembly.
The big nut doesn’t just hold the axle in, it keeps the bearing loaded and “together” too.