Transmission

[04UZJ100]

The stock fluid/air has ducting around it to keep mud out.. it is a pretty well protected unit. Plus if it became clogged the fluid/fluid in the base of the radiator should help at least somewhat..

Yep. Fun fact - This entire cooler was removed from the 5.7L Tundra all together. Toyota made the distinct decision to leave it in the Cruiser.

However, the 200’s cooler is smaller than the 100’s and is also routed through the radiator - which the 100s is not. The 100 has lower operating temperatures in the transmission than the 200….

 

[bloc]

Yep. Fun fact - This entire cooler was removed from the 5.7L Tundra all together. Toyota made the distinct decision to leave it in the Cruiser.

However, the 200’s cooler is smaller than the 100’s and is also routed through the radiator - which the 100s is not. The 100 has lower operating temperatures in the transmission than the 200….

The fluid/fluid one?

Total speculation.. but the cruiser is a 2-row radiator whereas the tundra is single row. I guess it's possible it just wouldn't fit into the lower tank.

Or more likely, they were trying to save money and thought it wasn't necessary.

 

[LC200JG]

The stock fluid/air has ducting around it to keep mud out.. it is a pretty well protected unit. Plus if it became clogged the fluid/fluid in the base of the radiator should help at least somewhat..

If I were to buy a cooler any recs from anyone?

 

[bloc]

If I were to buy a cooler any recs from anyone?

I'm really not sure how you'd improve on the stock system. It has two.. both a large air/fluid and a fluid/fluid inside the radiator.

I'd just make sure your stock air/fluid (the thing behind the grille on the passenger side with the plastic ducting) isn't totally full of bugs and mud.

We really have no idea whether fluid temps contributed to your issues. Before I went messing with the cooling system I'd at least use a bluetooth OBD adapter and an app like OBDFusion to log temps and see if they are climbing. Sometimes messing with the stock systems only makes things worse, since they are so reliable/durable.

 

[LC200JG]

I'm really not sure how you'd improve on the stock system. It has two.. both a large air/fluid and a fluid/fluid inside the radiator.

I'd just make sure your stock air/fluid (the thing behind the grille on the passenger side with the plastic ducting) isn't totally full of bugs and mud.

We really have no idea whether fluid temps contributed to your issues. Before I went messing with the cooling system I'd at least use a bluetooth OBD adapter and an app like OBDFusion to log temps and see if they are climbing. Sometimes messing with the stock systems only makes things worse, since they are so reliable/durable.

Thank you!

 

[bronc076]

Like bloc said the factory setup is good, my comment earlier was more of a general comment to maintain transmission health. Keep them cool with fresh fluid. Lots of vehicles only have the cooler in the radiator. So sorry if I sent you in a direction that does not need traveled. I would look through your grill with a flashlight and see how cruddy the transmission cooler is Though.

Thankfully no. It drove 80 mph all the way home. I only noticed it slipped under load. Going up "hills" on the highway.

In what gears does your transmission slip? Id change the fluid and filter, see how much crap is in the pan, and see how it drives.

 

[LC200JG]

Like bloc said the factory setup is good, my comment earlier was more of a general comment to maintain transmission health. Keep them cool with fresh fluid. Lots of vehicles only have the cooler in the radiator. So sorry if I sent you in a direction that does not need traveled. I would look through your grill with a flashlight and see how cruddy the transmission cooler is Though.



In what gears does your transmission slip? Id change the fluid and filter, see how much crap is in the pan, and see how it drives.

It makes a lot of noise. Mostly slips on the highway driving around town you never notice it. It does not make noise at slow speeds or even on the highway as long as you’re not accelerating hard.

 

[linuxgod]

FYI this is general info for you @LC200JG. Not sure how much will help but I figure it can't hurt. Most/all of this is based on the 6-speed, but I believe it applies to the 8-speed as well. I'm going to post this info, then I'll comment in a second reply

There are two temp sensors for the A/T. One is in exiting the torque converter (when the temps are the hottest) and the second is somewhere on the return and/or in or around the pan. I'm going to refer to these as the TC and pan temps, though I'd have to go look at the transmission diagrams to figure out exactly where in the path they lie.

Fluid from the transmission is pumped through the cooling system (exiting the torque converter, through the external cooler, then into the radiator cooler, before being returned to the transmission pan) by the engine. High RPMs will pump fluid faster. More on this later.

The LC transmission will generally run in the 180-195F range under normal operations. 195F is the normal engine operating temp, and because A/T fluid goes through the radiator second that ensures it's always at least at 195F when you're driving once warmed up. You could add a dozen external coolers before the radiator and they would do nothing for you so long as the oil temp coming out of the radiator is ~195F. The only things you could do to further reduce A/T temp are (a) reroute the lines to skip the radiator (which might leave you running "dangerously" cold in the winter), or (b) run in a lower gear (or 4L vs 4H) in order to get RPMs up and pump more fluid through the cooler faster.

Anyway, you'll sit around 180-185F in both the pan and the TC if you put the vehicle in park and leave it running for hours. That's no load on the transmission of course. If you drive for a bit you'll see the pan normally runs around 195F. The TC will get hotter anytime the TC is not locked, though how much hotter depends on the gear, speed, ambient temps, and general transmission load. In most cases normal driving will put it temporarily around maybe 210F at peak, but it'll cool back down into the ~195F range after a couple minutes if your TC locks up. If you climb a mountain pass and the truck downshifts into 2nd or 3rd (on the 6 speed... probably ~4th in the 8 speed) you might see it get into the 230-240F range during your climb. Most people don't see that unless they're towing though.

The A/T temp light in the dashboard comes on at 305F and goes off at ~270F, IIRC. Or maybe it's 275F. Anyway my perception from those numbers is that Toyota believes anything under 270F is not a big deal, since the manual pretty much says the fluid is lifetime for normal driving (not towing, not heavy offroad), but if the A/T light ever comes on you do need to change the fluid. To them 270-305F is the questionable range... if you got to 305F then the A/T will do things like force your transmission into a lower gear to lock the TC and force fluid through the system faster (higher RPMs!) until you get down to 270F. (Note that anything over 240F concerns me for any length of time, but I'm not a Toyota engineer and they probably do know best).

 

[linuxgod]

Ok so now my thoughts for you.

tl;dr - go change your A/T fluid. Do a full 13 quart flush, where you drain into a gallon jug, not a pan drain/fill (exchange). At 120k without any fluid changes I suspect your transmission fluid is burnt and you're slipping because there's no friction in the fluid. This is cheap to do ($150 in fluid) and will tell you a lot about the problem.

If you never saw an A/T temp light while offroad, you never got to 305F. That's not to say you couldn't have been running at 304F all day, but in my experience offroad I've not seen the A/T temps get nearly as hot as they do when I'm towing. Assuming your ambient temps were in the 90s outside or lower, 230F is probably the peak, give or take. Now if you're pushing the truck hard it's possible you're generating a lot of heat while not moving enough, but it's hard for me to believe you'd see temps significantly higher. Even 240F or 250F all day you wouldn't destroy the transmission, just the fluid in it.

That said as other have noted there have been a number of issues with the 8-speed. Toyota fixed some with firmware updates, but there have been some documented cases of transmissions completely going out on new 2016+ trucks a few years back where Toyota did full transmission swaps.

If there is some damage, I would question whether it's the whole transmission or just the torque converter. Granted the TC alone is pretty expensive, and if you have to drop the transmission to do it you might as well swap the whole thing.

Once you're up and running again, I'd suggest getting a cheap ELM 327 bluetooth OBD2 dongle and a copy of OBD Fusion and using that to watch your transmission temps, as well as engine oil temp and any other interesting data, when you're offroading. The dongle plus OBD Fusion and the add-on Toyota PID pack is maybe $50 total. There's info in my Towing with a 200-series thread.

Good luck

 

[LC200JG]

Ok so now my thoughts for you.

tl;dr - go change your A/T fluid. Do a full 13 quart flush, where you drain into a gallon jug, not a pan drain/fill (exchange). At 120k without any fluid changes I suspect your transmission fluid is burnt and you're slipping because there's no friction in the fluid. This is cheap to do ($150 in fluid) and will tell you a lot about the problem.

If you never saw an A/T temp light while offroad, you never got to 305F. That's not to say you couldn't have been running at 304F all day, but in my experience offroad I've not seen the A/T temps get nearly as hot as they do when I'm towing. Assuming your ambient temps were in the 90s outside or lower, 230F is probably the peak, give or take. Now if you're pushing the truck hard it's possible you're generating a lot of heat while not moving enough, but it's hard for me to believe you'd see temps significantly higher. Even 240F or 250F all day you wouldn't destroy the transmission, just the fluid in it.

That said as other have noted there have been a number of issues with the 8-speed. Toyota fixed some with firmware updates, but there have been some documented cases of transmissions completely going out on new 2016+ trucks a few years back where Toyota did full transmission swaps.

If there is some damage, I would question whether it's the whole transmission or just the torque converter. Granted the TC alone is pretty expensive, and if you have to drop the transmission to do it you might as well swap the whole thing.

Once you're up and running again, I'd suggest getting a cheap ELM 327 bluetooth OBD2 dongle and a copy of OBD Fusion and using that to watch your transmission temps, as well as engine oil temp and any other interesting data, when you're offroading. The dongle plus OBD Fusion and the add-on Toyota PID pack is maybe $50 total. There's info in my Towing with a 200-series thread.

Good luck

Especially after all of this information, and thank you, it is very confusing to me that it burnt up at all. Yes I was was locked. Yes I was in 4 low.

 

[linuxgod]

Yeah I'm frankly surprised that it would go. 3x locked in 4Lo or unlocked, the transmission impact should be the same - either the torque converter spins and generates heat and you go nowhere or it spins and engages and you move. If you're locked and not moving the stress is to the diffs or transfer case... the point of the torque converter is to spin but except when you get above 4th gear (in the 6-speed) or 5th gear (in the 8-speed) the torque converter doesn't lock up so there's no direct stress on the transmission.

Again I'd try a fluid swap with fresh ATF WS before dropping huge $ on a transmission swap. Unless you've already removed the transmission and broken it down and determined that there was damage, I would not be surprised if the fluid has degraded from the heat but the transmission is largely ok. Then again my mechanical skills for anything as complex as an electronic 8-speed A/T are probably worthless.

 

[LC200JG]

Yeah I'm frankly surprised that it would go. 3x locked in 4Lo or unlocked, the transmission impact should be the same - either the torque converter spins and generates heat and you go nowhere or it spins and engages and you move. If you're locked and not moving the stress is to the diffs or transfer case... the point of the torque converter is to spin but except when you get above 4th gear (in the 6-speed) or 5th gear (in the 8-speed) the torque converter doesn't lock up so there's no direct stress on the transmission.

Again I'd try a fluid swap with fresh ATF WS before dropping huge $ on a transmission swap. Unless you've already removed the transmission and broken it down and determined that there was damage, I would not be surprised if the fluid has degraded from the heat but the transmission is largely ok. Then again my mechanical skills for anything as complex as an electronic 8-speed A/T are probably worthless.

I will approach it again, but my technicians are certain it is torn up inside based on the noise.

 

[LC200JG]

I will approach it again, but my technicians are certain it is torn up inside based on the noise.

Yeah I'm frankly surprised that it would go. 3x locked in 4Lo or unlocked, the transmission impact should be the same - either the torque converter spins and generates heat and you go nowhere or it spins and engages and you move. If you're locked and not moving the stress is to the diffs or transfer case... the point of the torque converter is to spin but except when you get above 4th gear (in the 6-speed) or 5th gear (in the 8-speed) the torque converter doesn't lock up so there's no direct stress on the transmission.

Again I'd try a fluid swap with fresh ATF WS before dropping huge $ on a transmission swap. Unless you've already removed the transmission and broken it down and determined that there was damage, I would not be surprised if the fluid has degraded from the heat but the transmission is largely ok. Then again my mechanical skills for anything as complex as an electronic 8-speed A/T are probably worthless.

Okay he says when it is fully locked the transmission is the weakest link. With the pressure and force trying to get my 6,000 lb truck over an immovable object he could see where it might overheat the transmission.

 

[04UZJ100]

Okay he says when it is fully locked the transmission is the weakest link. With the pressure and force trying to get my 6,000 lb truck over an immovable object he could see where it might overheat the transmission.

Disagree. Maximum input torque in the transmission is from the engine, Not the wheels.

 

[bronc076]

Okay he says when it is fully locked the transmission is the weakest link. With the pressure and force trying to get my 6,000 lb truck over an immovable object he could see where it might overheat the transmission.

Disagree. Maximum input torque in the transmission is from the engine, Not the wheels.

What are you disagreeing with? If the truck is in gear, the engine is producing power, and the wheels are not spinning, the transmission is the only option to eliminate the rotation the engine is producing unless something else breaks. This occurs through the torque converter heating the fluid, or internal clutch packs slipping. Torque converter is designed to provide slippage sitting at a stop light, accelerating through the gears, towing, and other normal driving scenarios. However if one were to pump significant power into the transmission without wheel spin for a long period of time, something has to give. Sometimes it's an axle, sometimes it's a U-joint, sometimes it's broken gears. But typically, it's the automatic transmission converting RPM into heat.

The fact that the LC200CG is having trouble in higher gears while driving now leads me to believe a fluid flush would probably help.

What are the sounds it is making, and does it make it in all gears? Is is a high pitched sounds and in say 6th or 7th gear RPM increases with the sound? Or does it happen when the converter locks? There are a variety of things that could be wrong, but as others have stated, I would start with a fluid and filter change. It's frustrating that these do not have a dipstick, that is a handy tool to smell and view the fluid.

 

[bronc076]

If you're locked and not moving the stress is to the diffs or transfer case... the point of the torque converter is to spin but except when you get above 4th gear (in the 6-speed) or 5th gear (in the 8-speed) the torque converter doesn't lock up so there's no direct stress on the transmission.

This I disagree with. If you are locked and not moving there is equal stress on everything, axle shafts, driveshaft, Transfer Case, and transmission. How much force the output shaft of the torque converter puts on the input shaft of the transmission is transferred all the way to the wheels. Actually, the transmission would have more as the force is distributed through the drivelien to the 4 tires. Tire to pavement, transmission clutch packs, and torque converter are the only places rotation can be reduced.

 

[bronc076]

Here is a nice article on torque converters for those of you that are interested. The torque multiplication is interesting. This is geared towards drag racing.

Torque Converters - Unlocking The Secrets - Car Craft Magazine - https://www.motortrend.com/how-to/ccrp-0310-torque-converters/

 

[linuxgod]

This I disagree with. If you are locked and not moving there is equal stress on everything, axle shafts, driveshaft, Transfer Case, and transmission. How much force the output shaft of the torque converter puts on the input shaft of the transmission is transferred all the way to the wheels. Actually, the transmission would have more as the force is distributed through the drivelien to the 4 tires. Tire to pavement, transmission clutch packs, and torque converter are the only places rotation can be reduced.

IANAM - I am not a mechanic, I just play one on TV and the internet. So I may be wrong, but here's my understanding:

The transmission can slip; a locked drive line can't. I don't think the stress is equal for a number of reasons (gears multiplying the force for one, but also the ability for some components to slip and thus absorb some of the force). Your engine sends power through the transmission to the transfer case and then the diffs to the wheels. If you're triple locked and sending power to the right front wheel which won't move, the stress is at the wheel and thus the front diff. All the force (torque) is being applied to the part that is stuck (the RF wheel in this probably terrible example). If the wheel doesn't move you break a CV. If the CV doesn't break the force goes up the chain to the diff, transfer case, and transmission (and then engine). So yes there is stress to the transmission. However the torque converter slips, much like you partially depressing a clutch pedal, so it is absorbing some of that force as heat. (FWIW in the above example in an M/T you'd just stall if you didn't "ride the clutch" since the engine would try to turn the transmission and would immediately fail.

I would expect a lot of heat to be generated. How much depends on how long you're relying on the torque converter to slip, as that's where most of the energy goes (and thus the heat), which is why my first thought is the fluid is burnt and no longer allowing the proper amount of friction. Unless you were constantly on the gas and going nowhere I can't see generating enough heat to completely destroy the transmission. I'm not an ASE-certified mechanic and if a professional who the OP trusts says something is rattling around in there it is certainly possible that a gear broke or something, but I've also had ASE-certified mechanics I know and generally trust come up with the wrong diagnosis based on what the book taught them.

 

[airforce1]

As someone who needed a transmission rebuild at 93K, I would highly recommend a tranny flush regardless of whether it is a sealed system. My tranny rebuilder has seen many AB60s having given up the ghost due to inadequate ATF levels or burn ups.

 

[linuxgod]

As someone who needed a transmission rebuild at 93K, I would highly recommend a tranny flush regardless of whether it is a sealed system. My tranny rebuilder has seen many AB60s having given up the ghost due to inadequate ATF levels or burn ups.

I do tow a lot but $150 (plus an hour of labor... yours or a mechanic's) seems like cheap insurance to me.