The truth about differential and transfer case fluids

When your over 70 or so its hard to crawl under those trucks anymore. My wife has a new 2018 RAV4 with 14000 miles and the next (first) oil change is at 20k?

My last vehicle went to CARx here in town for oil changes and other work. I am sure that's where I am going to take my new to me 2015 Tacoma. They are honest and saved me a bunch when they found an in warranty by two weeks issue with my 2014 Silverado. Could have charged me but sent me to the dealer for warranty work that saved me $2k on rear axle repair!

 

FWIW, my earlier post about lubricant change intervals is based off of experience with and analysis I've done on various fluid systems. I've never done detailed analysis specifially with automotive drivetrain components, but I have seen (and analyzed) the affects of wear and lubricant quality first hand.

Not saying I'm an expert on the subject, but I'm basing my opinion on my experience in the engineering field. Take it for what it's worth (or not, just wanted to clarify ).

In my opinion, if you're on this forum, unless you're physically unable to, you should be changing your own fluids anyway. But that's just me.

 

Consider the following.

Most people drive about 15-20 kmiles/year. So, even at a 30 kmile interval, you change every 18-24 months. Cost for a DIY fluid change job on the diffs and Xfer case is roughly $50-60 and a couple hours rolling around under the truck. The maintenance cost is about $2-3/month. If just one of these components fails......the repair cost will be significantly greater than $3/month.

Automatic transmission fluid and filter change as a DIY job is even less expensive. Fluid and filter <$50 with a 100 kmile interval, so at 20 kiles/year, you change 1 time in 5 years. Cost is less than $1/month. Think about the cost of a major tranny repair...... $1/month is pretty cheap.

Sure, there will always be the 1 who has a bajillion miles on their truck and haven't done any maintenance. Just realize, this is not a typical circumstance.

Also realize the engineers who design and test these components spend 1000s of hours in testing and monitoring part wear and fluid life. I would be hard pressed to debate them on this topic. I am sure the engineers have a built in safety margin for the stated change intervals.

When I was in the power tool industry, our standard tool life analysis was based on the Wiebul process. We would define the warranty at a time when 10% of the tools were expected to fail. The "life" of the tool was the time at which 90% of the tools were expected to fail. This limits the warranty exposure, it also indicates that some tools would run well past the expected life.

I am in the camp of changing fluids and doing maintenance at or near the stated intervals. Its the best way to keep your ride out of the shop and keep operating costs low.

Do as you wish. Just understand what is being risked with extending or ignoring the service intervals.

 

Your argument is a small pyramid of fallacies built on each other. It’s actually quite impressive. Not Giza impressive mind you, but I have to give you credit for the effort.

 

I just stick to whatever the maintenance schedule says. A lot of conspiracy theorists think the manual gives bogus information for unnecessary work so the dealer can make money or no guidance at all to ruin your truck so you need to buy a new one but I don’t think that’s true. The first and second gens have gone a while but I don’t think we will know the true reliability of the 3rd gens for another 5-10 years.

 

This thread is different than I thought.............I don't think there is anything all that special about the requirements of the 3RD Gen TC, that make the Toyota Special Fluid a use or die proposition. It's just a very very thin oil with some EP/AW additives. I venture to say anything from a strong ATF to MTF gear oil will work. Sure, there is a chain (same as 2nd gen??) which could shear the base oil, but the switching in 4LO is all stop, so no synchro there and 4HI must have a simple synchro, yet is OK with the Toyota fluid and which should be OK with MTF. Been on MTF for awhile, zero issues. May swap and analyze at 25K, dunno.

 

If you do it yourself, the diffs and transfer case fluid changes are cheap and easy.

 

The easiest has to be the TC oil, get truck up on standard safe ramps, set up lawn chair under truck , make sure fill plug breaks free, drain, replace crush washer tighten drain plug, pump full, replace crush washer, tighten fill plug and admire handywork. The other holes are easy as well.

 

Ok - I need to bring this back up again. I checked the maintenance book and found that transfer case and differential fluids are only recommended to be changed if you do off-roading, dirt road driving, or towing. I don't do any of that...just city driving. Based on this, It doesn't seem like these fluids are required to be changed at all. Yet my dealer is pushing it. My taco has 91k miles.

The question is whether its really needed or not - based on the experience of people in this forum.

Yes yes yes, I know I can do it myself. I've seen all 20 posts telling me that its cheaper to do it myself. Thanks for the heads up. but that wasn't my question.

 

That's completely up to you, if it were mine I would change it just for peace of mind. Just my 2 cents

 

Do as you wish. The rear differential fluid is stressed. At minimum it should be changed. The front diff is just hardly if ever working, ditto the TC, and it is a sealed unit. But if used they are mechanical gears so need fluid changes at proper intervals. Again, modern synthetic lubes last a LONG TIME, change now and you should never need to change again.

Not exactly a precise answer, more my thoughts on the matter.

 

Any write ups on the power steering fluid and brake fluid with turkey baster or syringe? Sounds pretty obvious to me me just want to be sure.

What do you recommend for fluids in each of those?

 

sounds like you aren’t willing to do it yourself and/or can’t afford to have the dealer do it.

If you don’t WANT to do it then don’t, but you are just fishing for a reason to rationalize your decision.

At a certain point your manual isn’t going to tell you what to do. What then?

 

Do you intend to keep this vehicle as long as you can? If yes, changing the fluids is an inexpensive method to ensure you get maximum life out of these components.

Can you afford to do so right now? If no, then delay this until you can. Can you afford to do this every 100, 000 miles? Same as new tires, brakes? Then yes, do it.

 

I remember someone posting this video on a TW diff. thread and thought it gives some idea what stresses the rear diff. oil goes through at a slow speed.

https://www.youtube.com/watch?v=9-yG3D3JBRs&t

 

FTFY

 

excellent find

 

On my 05 4runner (close enough to tacoma) had the diff/tcase fluid changed at Toyota around 100k, then I bought it around 185k, and I changed them when I started learning about maintenance around 210k. It could have been changed in between either of those at a Firestone or whatever, but I don't know. The front diff was pretty low, but I don't have any diff problems now. That being said, I plan to change the gear oil every 30k-45k from here on out. I give this example not to say that you can wait 100k between changes, just that putting it off until you can afford (monetary and downtime wise) isn't going to instantly grenade your diff. I would recommend changing the fluid it at your earliest convenience.

An added benefit of the frequent changing is it will help to keep the front diff drain bolt from getting to stuck from sitting forever

I'm going to guess that the 4runner and Tacoma PS fluid systems are similar given they have same engine and very similar drivetrain, front suspension, etc but I'm not 100% sure. I've got some pics of when I did my PS flush in my build thread (not really a build, but working on it lol) linked in my signature on page 3ish. I used a top to a pump soap to empty reservoir. Also a thread called 4th gen Maintenance Tutorials, Write-ups, and Picture Threads in my signature over on T4R.org that has a writeup on PS fluid in there. Sorry for the scavenger hunt, can't get to T4R.org right now lol

I used maxlife atf for my PS

 

At 30k i changed rear, front and TC fluids. I forgot to do them again at 60k. I'm closing in on 90k now and will do them all again then. I don't think it will hurt anything but am also not advocating waiting. I just forgot and its one of those things on the back of my mind. My truck doesn't see any off-road abuse and actually doesn't see much 4x4 action period. Mostly use 4x4 in the snow during ski season. Either way you're probably fine as others have stated, but it definitely wouldn't hurt to stick to the recommended maintenance schedule. And yes, do it yourself. Super easy.