Thoughts on front diff needle bearing failures

I have watched a few videos about the 4 Runner front diff. One front East Coast Gear supply. Apparently the spider gears and their mating surface is cast. A DANA diff has machined surfaces vs Cast. The guy said with a machined dimension the support is predictable and more precise. If I am not mistaken, the tolerances on castings may not provide a good bearing support surface which can put more load on the needle bearing leading to more wear. Many here , including myself, wonder why don’t all 4 Runners have the problem, even those not lifted. Perhaps it is as random as how the tolerances stack up on our individual 4 Runners. Besides that reason, if the needle bearing isn’t adequately lubricated, it would have issues. My 4 Runner was 3/4 quart low in the front diff, when new. It only holds 1.6 quarts. I was under my 4 Runner looking at the fill hole elevation compared to the needle bearing. Seems to me, a serious under-filled condition might compromise the diff bearings (needle bearing on drivers side, ball bearing on passenger side). One could argue if any of the bearing is wetted it would be adequately lubricated spinning in oil. There doesn’t seem to be many problems on the passenger side. I would highly recommend verifying your front diff is adequately filled soon after getting your 4 Runner. Waiting until you replace the gear oil (perhaps 30K miles or more) could result in unwanted wear. My 2016 Tacoma TRDOR was also under filled but only 1/2 quart vs 3/4 quart. All other fluids were filled correctly on both 4 Runner and Tacoma: rear diff, transfer case and transmission. When I stuck my finger down in the fill hole I could not get gear oil on it. I checked mine before I had 100 miles on it.

 

Try this on a Google search:

needle bearing issues site:4runners.com/

A lot of input on this issue.

 

We replaced our needle bearing with the ECGS bushing. Upon inspection, we noticed alot of clearance between the bearing and the machined surface of the axle, the bearing itself looked new, it had gear oil on it. Then we tried to put the bushing on the axle and found a much tighter fit, with little clearance between the axle and the bushing, enough to lubricate it, installed it, and the problem(a harmonic type fluttering sound) went away. I do not know where you're talking about cast vs. machined surfaces though. While certain parts are cast at foundries, the parts that are cast in the front diff./axle, have machined surfaces where bearings or bushings would meet or have rotational contact. There is a bunch of info concerning the needle bearing on this forum, as well as other forums.

 

Did you guys have any trouble applying factory required torque values to all bolts/nuts? I have the torque values. If doing job alone seems like some would be difficult? Like the axle nut under the hub dust cover is 174 ft-lbs. seems like either another person need to be in vehicle applying brakes (pads grabbing brake rotor) or install tire and lower jack until tire contacts ground? I guess you just figure it out as you go along. I don’t have the symptoms of failed needle bearing but if I get them I plan on doing repair myself. Never done a CV axle replacement but appears doable with all the U-Tube video’s available.

 

Just put a couple lug nuts on and put a pry bar across them, and you will be able to torque down the hub nut

 

Tire on the ground is one way. Big screwdriver in the brake rotor vanes wedged against the caliper is another way.

If you grease the axle nut threads, the torque is reduced to ~115 ft-lb and more manageable. Do not overtighten as that will shorten wheel bearing life.

The most time-consuming part of the job is hammering in the ECGS bushing.

 

If you get the insertion tool, don’t you just keep tapping until the tool bottoms out on the face?

 

Oh rebuild it don't replace with Chinese stuff. Toyota has rebuild kits for $48 each online wholesale thats best axle made. If it's just a boot leaking and not torn, give it a little grease with a needle under the boot and reclamp. They may not rebuild stuff at every dealership. We had mechanics first and technicians next. Technicians make you look good and mechanics get work done. I watched them rebuild a rack but $288 for rebuilt Toyota and that's not to bad. I might collect one for what if. $788 new