Front Diff Vibes ECGS bushing fix.

41301-35230 - Case, Front Differential (2016-2017 All, 2018-Jan. 2019 Excl. TRD Pro)
41301-71120 - Case, Front Differential (Jan. 2019-2021 Excl. TRD Pro)
41301-35240 - Case, Front Differential (2018-2021 TRD Pro)

41039-35010 - Gear Set, Spider (2016-2017 All, 2018-2021 Excl. TRD Pro)
41039-35020 - Gear Set, Spider (2018-2021 TRD Pro)

I have no idea what the differences are, and the 2018-2021 TRD Pro parts are not used in any other Toyota vehicle.

Jeff

 

It's really a matter of perspective. From a "wanting to lift the truck" perspective it's not great, but the spider gear and the spline is not intended to support radial loading from the CV spline, that's what the bearing is for, but again, it's not designed for misalignment forces.

Jeff

 

It’s cost savings plain and simple. Mass producing a cast part with loose tolerances is cheaper than a machined precision fit that would prohibit misalignment forces in the needle bearing

 

Yup, that's exactly what I'm saying, you don't precision machine a part that doesn't need to be machined, it's a waste of money. The spider gear is designed to be supported by the CV shaft, it is not there to support the CV shaft. The spider gear is not supposed to touch the case as it was designed. They designed the differential for the forces they expected it to see and excluded cases they didn't. That said, if they did design it for those forces, it would have been with a second internal bearing and/or larger outer bearing. The needle bearing is there because Toyota doesn't want consistent metal on metal contact between the always spinning LH CV and the not always spinning front differential in ADD front diffs.

Splined connections are not typically designed for radial loading, and so applying that loading and then trying to support it with steel on steel surface contact between the spider gear and the case without pressurized lubrication would seem to be ill-advised, at least to me.

I would suggest deleting ADD and going with a traditional diff, or perhaps machine the diff/spider gear to accept a bearing (ball or plain if there are geometry concerns) if you are going to apply those increased loads to the spider gear. I'm not sure if that is what ECGS was planning to do when they took it apart.

Jeff

 

None of your suggestions are practical for anyone just wanting to eliminate vibes after a lift. What “traditional” diff would even fit? Besides, the ECGS bushings doesn’t net you steel on steel, it’s a sintered bronze bushing.

FWIF, the Dana 30 carrier is machined for a much more precise fit of the spider gear.

 

What's practical depends on the person I suppose, though I agree for most typical owners my suggestions aren't the most straightforward, though I would say the most practical of them is probably using a non-ADD differential, you could find one used pretty easily I would think.

For finding one, in North America, a traditional diff could be sourced from a 2003-2009 4Runner V8 (3.73:1), 2003-2009 GX470 (3.73:1), 2007-2014 FJ Cruiser 6MT (3.91:1), 2010-2021 4Runner Limited/Nightshade (3.73:1), or 2010-2021 GX460 (3.91:1). These diffs are all bolt-in for a 2005-2021 Tacoma and do not use the needle bearing setup.

You're right, the ECGS bushing is not steel on steel and serves the same purpose the stock needle bearing did, but that wasn't what I was getting at to be honest.

In a traditional differential setup, like you would find in a Dana 30, or a non-ADD Toyota, when traveling in a straight line with the hubs engaged, the diff and axles are spinning at the same speed, so there is no relative motion between them. When you start to take a corner, the inside wheel moves a bit slower and the outside wheel moves a bit faster, with the diff moving at their average speed. The relative speed between the diff and each axle is half the difference between the inner and outer wheel, which is pretty slow and easy to lubricate.

In contrast, with ADD the RH axle is disconnected, and so when driving in a straight line, the LH axle is spinning at full speed while the differential is stopped, this results in the spider gears spinning inside the differential at full vehicle speed, and so Toyota machined the differential case slightly larger and put in a needle bearing to allow that full speed relative motion between the moving CV shaft and the stopped differential.

If Toyota had machined the case and had a precise fit on the spider gear into it, that spider gear would then also be spinning against a stopped case at full vehicle speed. This is also why there is a needle bearing on the RH side of the diff, as that (disconnected) stub shaft is also spinning at full vehicle speed. The other spider gears ride on a pinion shaft with two slots to allow oil to get in. There is very little loading on these gears during disconnected operation. This is what I was getting at.

If it were me trying to solve the problem, my first thought would be to try to get a second bearing installed outboard of the differential in the area where the oil seal is installed. It's a tight area to try and make something like that happen in, but it would provide the support needed instead of overloading the needle bearing, additionally it could be done in vehicle without too much trouble.

Jeff

 

Oh, that’s what you mean by traditional diff. Gotcha, yeah those will fit but you will then end up with a diff, front drive shaft and xfer case that always spins. Even in 2Hi. Driven by the tires, with worse mpg as a result. How much worse I can’t say. Never tried on my trucks. It probably changes the road feel too, at least slightly but maybe not everyone will notice. I don’t mean to lecture you, sounds like you’re well aware but you didn’t state this in your post above. So what did you do on your truck? Factory CV angle? Or did you use one of those AWD non ADD diffs? Do the latter use a 2 or 4 pinion design?

 

Yeah I am aware of the changes it would make, figured it was a given. Definitely would have the diff, shaft, and t-case spinning all the time, which would hurt your fuel mileage a tad. With an open differential in there I don't think you'd notice a difference in the way the truck drives, each of the front wheels is free to spin completely independently from the other. There is a small difference of course, with the added drag losses of the spinning drivetrain components, but likely not noticeable from a road feel perspective.

As for me, I've never had a lift large enough to cause issues with the bearings. My interest is almost purely from a design/engineering interest standpoint, though I have also in the past had to help other people fix their trucks or just help when they're deciding how to set up a lift, etc.

From time to time I do take the time to develop an actual product and/or solution to these issues as well, and I'm hoping once I am done my last semester of classes in April, I'll be able to use some of my time to doing that a bit more.

Jeff

 

Same here, I have less than 1” suspension lift. Not a fan of lifted trucks, and I’ve had no need for ditching the needle bearing. So do you know if those ‘conventional’ diffs are 2 or 4 pinion?

and if one were to go ADD delete, either with the Taco clamshell or a donor from an AWD Yota, what is your take on throwing a Torsen into the mix up front?

 

Sorry I missed that part. The pinion setup and the spider gears are the same for with or without ADD, so they are still 2-pinion.

Jeff

 

So, same as the open rear diff. I was asking because both the available ARB air locker and the Harrop e-locker utilize a 4 pinion design (in the rear as well) but curiously the Harrop unit uses OEM style needle bearings (on both sides) but the ARB does not.

 

Do you need the install tool or just the removal tool?

 

Fuck I am an idiot and decided to change the seal as well. I guess it didn't go in evenly. How likely is this to leak? somewhere between definitely and probably. I mean she is absolutely in there and tight now.

 

I'd say you're more likely to leak from a rusted out hole in that diff... good lordy that's bad.

As for the seal, it's kind of hard to say, but I think as long as it makes good contact with the CV, you'll be fine. I'd just install the CV axle and keep an eye on it for a little while.

 

Hey be nice. Its not that bad. I guess I already knew the answer goin in. Luckily my local had 1 more in stock. Second time around I am going to clean the edges of the opening where it contacts. I feel like it just caught on the rust or something. Also didn't go in too evenly.

 

Holy rust! what does the rest of the underneath look like?

 

Alright fuckos! enough about the rusty boy. Operation went well I think after putting another seal in there. New CV aslo. Frame recall in 2017. Some areas still have more surface rust than others. Front Diff being one of those places.

 

Hey, Folks.

With some help over the weekend, I got the bushing installed, but I was dumb. I replaced the seal and got some nice leakage because I think I drove it in a bit too far. I had to do this to square it up. Last night, I swapped in another new seal and got it square and flush to the diff surface. There was a lot of lube in the area and all over the seal. After a 8mi test drive, I had a small dribble out of the fully filled diff. This morning after a 15mi drive, I got a similar amount. Not enough to dip off or run.

From folks that have swapped the seals, is this common?


I should have left the factory seal. At over 50k, I thought it might have been smart to swap. Oh well.

Thanks!

 

Hey, Folks.

It looks like I'm good to go. The small dribbles must have been lube on the outer face of the seal during installation. It is looking good now.


If folks go further than flush with the seal, expect trouble.

 

Not sure where else to post this but I recently encountered 2 instances of a bad needle bearing on my buddies trucks. Both 07s both lifetime bone stock suspension, standard size tires. I think both trd sports too.

Also both had seriously deteriorated needle bearings and a ton of play in the driver side axle, so I guess having a lift could accelerate the problem but they were both really bad like mine was. I don’t think there’s much difference between stock and lofted as far as that bearing going bad. It should probably be a tsb but that’s another discussion. I know this is all gen2 evidence but we’re all rocking the same malfunctioning part, so there you go. Happy (vibe) hunting gents!