Drive Train Fluids - Suggestions and Questions

[BlackWorksInc]

Asssuming the transmission holds 12 qts total (FSM is somewhat ambiguous, but that's close), and you drain and replace 4 qts each time you do it, then the percent of new fluid is given by the following formula

100*(1-(8/12)^N), where N = number of times you drain/fill.

Example. 1 drain and fill. (8/12=.667)

%new fluid = 100*(1-.667^1)=33%

Example: 3 drains and fills

%new fluid = 100*(1-.667^3) = 70%.

And so on... Takes about 6 cycles to get to 90%.

My plan going forward is to do a drain-fill at each oil change for the next 3 changes, and then every 3rd oil change after that. That should pretty much turn over the fluid every 100K miles, which for my driving model (<2000 miles of light towing/year) should be adequate.

I think that's a bit overkill, as I pointed out before it's not at all about getting all the old fluid out (you can't, not unless you take apart the transmission and scrub every last spec of varnish/grime off all the components); but replenishing the additive packages and majority of the fluid. You can't do a 100% fluid exchange no matter what you try, which is why Toyota is find with just drain & fill a couple time.

But it's your vehicle and if that's the service interval you want to use, it's not gonna hurt anything to do that. I personally am going with 100k and then 50k intervals to match the coolant service intervals (first coolant service for all Toyota vehicles using SLLC "Pink" is 10yr/100k followed by 5yr/50k intervals).

 

[RonJR]

You're probably right, but if you go back to the oil analysis I posted earlier in this thread, my fluid has a pretty high metal content currently, which is why I want to be a bit more aggressive early on with the drain/fills to get things cleaned up a bit. I'll send another sample in for analysis after two more drain/fills, see where I am, and go from there.

Thanks for your insights.

 

[wfo9]

I'm just amazed that OP is changing tranny fluid at 30k miles. That is crazy and a huge waste of time and money. ~100k makes sense.

 

[catrains]

You're probably right, but if you go back to the oil analysis I posted earlier in this thread, my fluid has a pretty high metal content currently, which is why I want to be a bit more aggressive early on with the drain/fills to get things cleaned up a bit. I'll send another sample in for analysis after two more drain/fills, see where I am, and go from there.

Thanks for your insights.

I am not going to do the drain and fill tranny fluid method . my plan is and on other vehicles drop tranny pan . clean up the pan and the pan magnets .

then add the same amount of fluid plus 1/2 qt . run it and check for proper level.

it is more work but the metal from break in and machining of new is mostly removed.

a new tranny will have more metal in the fluid..

flushing is good if its contaminated like antifreeze or water etc...
I would never flush with a dirty pan.

 

[jstim]

Speaking of fluids....here's a question for you all. I have heard a rumor, from a mechanic. I'm considering changing the gear oil in the front and rear diffs to Royal Purple. I have a 15 TEP and it has the locker, but I was told if I shy away, and use the other fluid, it will ruin the locker. My mechanical brain says this is hot garbage, but I want to know if anyone else has seen or heard anything like this? I absolutely do. Or want to have to buy a new locker over some damn fluid.

 

[wfo9]

Speaking of fluids....here's a question for you all. I have heard a rumor, from a mechanic. I'm considering changing the gear oil in the front and rear diffs to Royal Purple. I have a 15 TEP and it has the locker, but I was told if I shy away, and use the other fluid, it will ruin the locker. My mechanical brain says this is hot garbage, but I want to know if anyone else has seen or heard anything like this? I absolutely do. Or want to have to buy a new locker over some damn fluid.

Locker requires no special lubrication. Someone probably getting limited slip mixed up with a mechanical locker.

I run Lucas 85/140 non synthetic in mine. It's not the best for mpg, but helps with off-raoad use.

 

[jstim]

Locker requires no special lubrication. Someone probably getting limited slip mixed up with a mechanical locker.

I run Lucas 85/140 non synthetic in mine. It's not the best for mpg, but helps with off-raoad use.

I am on the fence with what I want to use, Amsoil, Royal Purple or Lucas. I just want to make sure that having a good feeling putting the fluid in, is going to make my pocket feel bad later....

 

[1engineer]

I am on the fence with what I want to use, Amsoil, Royal Purple or Lucas. I just want to make sure that having a good feeling putting the fluid in, is going to make my pocket feel bad later....

Why not OEM? Just use what they do and there are no problems or issues.

 

[jstim]

Why not OEM? Just use what they do and there are no problems or issues.

That is an option, I always look to see if there are better options out there though. As an example I used to use royal purple in all my diffs in several other vehicles because it's good up to about 50k. Otherwise, and I'm a pretty firm believer in changing the other fluids every 30k. That just happened to be an example where they made a superior product. But I'm kind of feeling my way through this one...my 5th gen that is.