2025 Tundra Engine is down!

Or, the stacked tolerance evaluation did not cover the manufacturing flow extremes.

 

No, We know motors are being replaced because of a bearing failure. The symptom is a knocking motor lol

 

Wrong again. Plenty of failures that happened without “knocking”.

 

Good lord boys, do we even know what we are arguing about ? Lol

 

Well the sky isn’t technically blue either….the motors knock, or seize from a bearing failure. The symptom is the knocking or locked up….is that better.

 

Are they the Teenage Mutant Ninja kind?

 

@UncleBif'sAIvatars

 

Toyota’s ambiguity continues to be justified

 

That's the only kind

 

Stacked tolerances is something I’ve been dealing with consistently as an engineer as we push the envelope for efficiency. I don’t think this is something that is well taught in engineering anymore, if it at all. I wouldn’t be surprised if that is it.

 

Relatively recent mechanical engineering grad here. University of Colorado didn’t really touch on tolerance stackups. Only a tiny bit in my senior design class. It’s much more complex than it seems when you have so many components working together. I remember thinking “oh well you just min max the tolerances” but I didn’t consider pin/hole clearances until I had to do a stack up at work. Now, add in rotating assemblies with harmonic frequencies / non-straightness across bearings… that’s when it probably becomes FEA time using different high/low tolerances… but if you make one wrong assumption, you could be missing something huge. Add in time constraints, lack of resources during covid, confidence/reliability calculations, and of course money. There could’ve been an assumption/calculation made long ago that hasn’t been questioned yet.

 

Lol, what are you talking about? That wouldn’t solve a main bearing failure due to contamination. You would see an upper rod bearing failure and piston/cylinder damage if the actual tune was the problem, multiple people have posted pics of their spark plugs at the 40k interval change and they look perfect. You’d see damaged spark plugs if the tune was an issue. Stop peddling nonsense. Also multiple videos showing the engine swap being done on YouTube, you wouldn’t need to swap the ecu, just upload new software. Modern engines have knock sensors, the ecu would pull timing on its own if it sensed any pinging or misfire. Modern engines will literally go into a limp mode annd self limit if any misfire is detected for a certain period. This was demonstrated when people installed the TRD intakes without the performance tune. The truck went into limp mode and wouldn’t make power, every word of what you posted is just flat wrong.

 

you haven’t been paying attention to the engine tear downs or this thread have you?

 

Yes I have, none of the failures indicate an issue with the tune. The rod bearing issue would be secondary to piston/cylinder damage. Once again you don’t know what you’re talking about. The majority of the issues are spun main bearings, from the oil system being contaminated, specifically main bearing number 1. The contamination has caused spun and damaged rod bearings, but where is the cylinder and piston damage? All I’ve seen is excessive skirt damage from metal being in the oil system, no damage to piston crowns, no metal missing from the combustion chambers, zero indication of detonation and pre ignition. The reason some engines have main bearing failure and some have rod bearing failure, is get this, machining debris being left in seemingly random areas of the oiling system, just like Toyota said.

 

Not being an engineer, I went down the "stacked tolerance" rabbit hole and I believe I now have the definitive answer as to why the V35A is blowing up. Toyota is using AI to design their motors. That's it, we can all quit trying to figure it out. Your welcome, now go drive whatever truck you own, to your favorite past time.

Seriously though, as I was reading and trying to understand the principles behind the tolerance thingy, I was thinking that I have always had (and especially since Covid) a rather healthy skepticism towards "modelling", and how flawed it truly is. Think "climate" modelling etc.
And how engineering has become I would suspect increasingly dependent on modelling. Not all models are bad or inherently wrong and without it, you engineers would have a hard time designing the crazy things we get to enjoy in our daily lives. But my skepticism comes from maybe young, inexperienced engineers blindly trusting their modelling software without ever really knowing what it is calculating behind the scenes, and never questioning the results they are seeing.

It's a long time ago, but we weren't allowed to use calculators in school until we could prove through testing that we knew long division etc. Modelling use today is taken to the extreme of that example but the principle applies.

 

Agreed. Especially since the real world difference between the two is 3mpg and they went with lighter/narrower tires on the new truck (265/70R18).

 

I wonder how many of these engines were put through dynamic testing in their development? I would have to assume in the hundreds. This would be the step used after modeling was taken as far as it could in order to validate the variables and constraints used in the model.
Deficiencies in either the design or part fit up (stack up tolerances) should have been addressed. I am now of the belief this really is an assembly issue, especially if human hands get in there.

 

Can probably all be traced back to GD&T issues, ASME Y14.5 has introduced a series of problems when interfacing between design, implementation, and manufacturing because it's a different language altogether. I run into issues with it weekly. Great concept, implementation has led to some major issues.

 

For those not jumping between two threads; went and saw my truck today; motor is torn down, it was a #5 bearing failure.

In complete contrast to what my service writer told me last Thursday, I'm not getting a whole motor, it's simply the short block and timing cover (and gasket set, and oil filter, and oil, and coolant). All parts arrived last Thursday, and the best timeline the service manager could give me today was that it would be ready "sometime next week". Also, since it's Tuesday... Happy 3 weeks since I last drove my 10 day old truck!

 

#5?? Sooo..... rod bearing, not crank bearing correct?

 

So it was a rod bearing failure then. Interesting.

 

Correct... The block was pushed to the side and honestly I didn't peak in and take a good look, but the crank was still in place when he pointed

 

Hmm. Interesting.

@yakeng and @chrisgibbs707 may be onto something with the stacked tolerances.

@G3ardnut - This is a question that needs to be answered. There is no way that they didn't experience failures during the development and testing of this engine.

@2wheelsforfun - This has been a thought in private discussions with engineers. Reminds me of Ford v. Ferrari. The yarn test for downforce and lift.

 

So should the rest of us 2025 owners be concerned then still? Lol or do you think this incident was a one off thing?

 

@sudobash you may be able to speak to this... What's the reason the front timing cover (11310-F4010) is replaced in this process?

 

Appears the "replace everything oil touched" does not apply here?

 

they will replace that because oil passes through it

 

Not even close

Although, in speaking to the Toyota brand engagement rep today, and expressing my continued disagreement with just the short block, I pushed the fact that there is precedent for those with similar failures to have the short block done, and then very shortly there after, going back for another motor presumably due to debris still residing elsewhere... She agreed without hesitation that that's true