Transmission overheated multiple times up in Death Valley and the Eastern Sierras (CA) this past weekend.
61k on vehicle now. Magnuson Supercharger installed at around 40k miles (probably not relevant). Replaced factory trans fluid at around 9k miles (yes I know supposedly a lifetime fluid) with Valoline MaxLife ATF (full synthetic). My buddies stock SR5 had no issues.
It was warm on a slow climb in low gears (2Hi or 4Hi). Nothing close to as steep as what the vehicle can handle. Just going slow as it was a both bumpy/rocky and somewhat steep. It was basically a single lane dirt fire/access type of road. Vehicle was full of camping gear, food, water and 2 little ones. Nothing being towed. It was warm but not above 95 degrees. I kept going for a mile or so driving more gently after the first episode. No limp mode or forced stop (don't know if our trucks do so). Warning message was gone after leaving the truck sitting (engine off) for 20-30 minutes. Continued on up to the 8k foot summit without recurrence.
On the second overheating, similar conditions, I stopped immediately and the warning message was gone after a very short cool down, maybe 5 minutes max. It did not come back over the next 2 hours of climbing up to 10k feet.
It seems that the SC intercooler blocks some considerable portion of the stock radiator (which as I understand it houses the transmission cooler), but largely speculative if this could be the cause or a contributor. I do also have some much bigger rubber than my buddy, 285 70 R17 BFG K02, but also doubt that is a factor. Anyone else experience this? I can't imagine I need an aftermarket trans cooler. I have not checked trans fluid level.
unless you regeared, this is your issue. if not the entire issue, a large part of it.
So if it was the inter cooler blocking air flow, whats the fix? Duel fans, moving the trans cooler, larger radiator?
The transmission cooler is a liquid to liquid cooler circuit where the ATF is run through a heat exhanger with the engine coolant in the bottom of the radiator.
The inside looks like this (the one on the left):
If the engine isn't overheating - the transmission cooling circuit is usually cooling as well as it can given the design. A larger primary engine radiator would have no benefit unless it was producing significantly colder coolant temps at the bottom of the radiator where the transmission cooling heat exchange is. A separate transmission cooler can add additional cooling capacity. The shared radiator circuit has limits. None of those options would overcome an internal thermal runaway problem.
The other way to help cool the transmission is air flow over the actual transmission. Some skid plates will block air flow more than others.
Different oils have different lubrication properties. The wrong ATF results in clutch packs that slip more than they do with the correct fluid and create a lot more heat. This isn't rocket science. If you put brake fluid in your differential - it isn't going to last very long. If you put rotella in your gas engine - it isn't going to last very long. And if you put the wrong ATF in your transmission... guess what?; it isn't going to last very long.
It doesn't have to be OEM Toyota fluid - but it DOES have to be the correct fluid. And currently only Toyota, Aisin, and Ravenol (possibly) make the correct lubricant for these transmissions. Valvoline ATF is about as close to WS as 5-20 engine oil. As explained in the video if it's T4 compatible - it is not compatible with WS fluid.
Also FWIW - Toyota WS is actually pretty cheap. Less than $10/qt.
EDIT: After a search there are a few other "WS" fluids at least on the label. Idemitsu claims to have one that is WS formulated (and not T4).
Rotella is fine in gas engines. A lot of the turbocharged crowd even uses it.
The transmission cooler is a liquid to liquid cooler circuit where the ATF is run through a heat exhanger with the engine coolant in the bottom of the radiator.
The inside looks like this (the one on the left):
If the engine isn't overheating - the transmission cooling circuit is usually cooling as well as it can given the design. A larger primary engine radiator would have no benefit unless it was producing significantly colder coolant temps at the bottom of the radiator where the transmission cooling heat exchange is. A separate transmission cooler can add additional cooling capacity. The shared radiator circuit has limits. None of those options would overcome an internal thermal runaway problem.
The other way to help cool the transmission is air flow over the actual transmission. Some skid plates will block air flow more than others.
Being in 4lo in these situations where you're slow going for a long period uphill will help moderate transmission temperatures as there is less slipping higher in the power band than when you're grunting along at low rpm. It will also allow the fan to kick in at a higher RPM and move more air through the engine/transmission radiator. Not sure if the fluid change makes any difference, only thing I can think of is if when it was changed, it wasn't filled properly and is low on fluid. Less fluid=less ability to disperse heat. Something to consider.
There is plenty of discussion online on Maxlife ATF vs. WS ATF and plenty of empirical evidence that it is perfectly fine in Toyota ATs. I think Maxlife is superior for the same basic, well established reasons that synthetic motor oil is better than conventional. Some also have pointed out that Maxlife has/likely has a superior additive package.
Well we’ve got 190K miles on the Maxlife synthetic ATF and no problems. Scoreboard beats internet know it alls who really know nothing. The Toyota OEM oils are simply rebranded product from the major oil company’s.
Well we’ve got 190K miles on the Maxlife synthetic ATF and no problems. Scoreboard beats internet know it alls who really know nothing. The Toyota OEM oils are simply rebranded product from the major oil company’s.
Do you really want to compare your cute anecdote to hundreds of millions of miles of testing? If it helps my last 4runner had 200k on the original fluid. And no problems. So have tens of thousands of them.
The unusual data point is an overheating transmission. The obvious answer is obvious.
im going with reduced airflow to radiator.. while rock climbing how much air could you possibly be moving to cool the radiator? It's completely relying on the fan. In stock form the fan moves plenty of air to keep temperatures moderated but now you've got an oil cooler which is ultimately trying to dissipate its own heat and pulling right back into the radiator.
When you say check fluid level, did you properly adjust the fluid at the right temperature?
Being in 4lo in these situations where you're slow going for a long period uphill will help moderate transmission temperatures as there is less slipping higher in the power band than when you're grunting along at low rpm. It will also allow the fan to kick in at a higher RPM and move more air through the engine/transmission radiator. Not sure if the fluid change makes any difference, only thing I can think of is if when it was changed, it wasn't filled properly and is low on fluid. Less fluid=less ability to disperse heat. Something to consider.
Throwing this out there before it gets lost lol
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I do keep track of my trans temps. On a modded T4R, it is not really difficult to push trans temps up once you push the truck harder while loaded. Thankfully, haven't seen any warning lights, but planning to do a trans fluid swap with the Toyota stuff.
Back to OP's scenario, and assuming the purpose here is to solve this and not start another fluid X vs stupid OEM stuff debate, let's start by summarizing some facts:
1. truck is fully loaded for a trip + steep incline = high load on the transmission
3. supercharged setup = added demand on transmission by means of higher engine torque output
4. Slow drive/ airflow blockage impedes transmission cooling.
Our transmission cooling is mainly based on 2 parts:
a. The in-radiator heat exchanger passing heat to/from trans and engine coolant fluids. Coolant is usually ~190f to 194f, and
b. Good airflow around the transmission body.
5. Warm days/ hot surfaces under the sun worsen #4 above
Basically, I believe OP scenario above is pushing the stock transmission cooling loop beyond its capability. OP using a non OEM ATF, for better or worse, is at least a variable at question here
Potential solutions:
1. Swap back OEM ATF fluid, flush lines and inspect for any blockage
2. Add trans temp monitor and keep track of temps. Higher than average temps for extended periods can degrade the ATF life
3. Consider added cooling for trans by adding an in-line cooler.
Do you really want to compare your cute anecdote to hundreds of millions of miles of testing? If it helps my last 4runner had 200k on the original fluid. And no problems. So have tens of thousands of them.
The unusual data point is an overheating transmission. The obvious answer is obvious.
Yep reduced airflow on a cooling circuit pushed beyond its thermal limit by an added supercharger. Non-OEM Synthetic ATF had nothing to do with this and never will.
You’re fixated on a damn manual that specs OEM fluids made for them by the same manufacturers of off the shelf fluid. They know this works on simple minds.
Yep reduced airflow on a cooling circuit pushed beyond its thermal limit by an added supercharger. Non-OEM Synthetic ATF had nothing to do with this and never will.
You’re fixated on a damn manual that specs OEM fluids made for them by the same manufacturers of off the shelf fluid. They know this works on simple minds.
it comes down to this
----------------------------------------------
use which fluid ? a or b
a--[what aisin and toyota engineers and materials scientists formulate as the fluid to use]
vs
b--[what some team of unknown and unaccountable random ****wits trying to reverse engineer what toyota paid millions for recommend, because it's a conspiracy]
Do what you wish. My transmission doesn't overheat....
Linear Mode
