Trans Overheated

[kcdehart]

Hey all

Was exploring some trails last weekend and ended up having to back ~1/4 mile in 4WD up a steep, very tight trail to find a turnaround spot (tree across the trail stopped progress). When I got turned around I noticed that my Trans Temp light was on (meaning the fluid got stupidly hot). I put it in park and let it idle to circulate the fluid and the light turned off after the longest 30 seconds or so of my life (warning lights when you're a 40 minute drive from the nearest cell service are NOT fun).

Should I do a fluid change or flush ASAP? I'm at 180k miles on (as far as I know) the original fluid.

Pros/cons of a flush vs an exchange? I always hear horror stories about flushes, so figured I'd ask for input.

Was a great trip, otherwise

 

[Falcon3]

180k original? Get it changed ASAP. If you’re comfortable, do the trans cooler hose exchange with 15 quarts of WS and be done. It uses the normal pump so no flushing. The dealer can also do this, and it shouldn’t hurt anything. Mine was done by dealer at 170k after it developed the shudder, and a hard 10k later, it’s still going strong.

 

[kcdehart]

I'm assuming it's never been changed. At the very least, it's been 20k miles, since that's how long I've had it. I'll do a flush soon just to be safe.

What's the shudder you mentioned? FWIW it drives great, no slippage or anything like that.

 

[ElZilcho]

It definitely won't hurt to change your fluid but the test is simple.

Crack a line to the transmission cooler and smell the fluid. If it smells burnt... it's burnt. If it smells fine... it's fine.

Toyota calls it "lifetime" transmission fluid but in engineering parlance that usually means ~100K miles. Even if it seems fine, if there's no evidence of a recent (post 100K) transmission service, I'd change it.

Check the fluid in your front diff too. It's also not designed to be driven in reverse for long periods of time and would've been taking the bulk of the load if you were reversing uphill.

 

[kcdehart]

It definitely won't hurt to change your fluid but the test is simple.

Crack a line to the transmission cooler and smell the fluid. If it smells burnt... it's burnt. If it smells fine... it's fine.

Toyota calls it "lifetime" transmission fluid but in engineering parlance that usually means ~100K miles. Even if it seems fine, if there's no evidence of a recent (post 100K) transmission service, I'd change it.

Check the fluid in your front diff too. It's also not designed to be driven in reverse for long periods of time and would've been taking the bulk of the load if you were reversing uphill.

Yeah, I tested from the dipstick and it's brown/smells burnt. I'll do the change next weekend. Flushing brake fluid at the moment and the dealer that replaced a front caliper before I bought it put on a sh*tty aftermarket on and the bleed screw sheared off inside. So that's the fun for today...not leaking, fortunately, so I can still drive it.

 

[BackOff]

Even if this 'life time' stuff was good for 100k.
How old is your 2004 T4R now? 14 years...with the same fluid?
Mine was built in '03 its just at 75k now.
Haynes repair manual states 30k or 24 months for trans. 15k if operated in 'severe' conditions.

I know it seems a bit much but that's what the book says.

Not sure who started this myth that you should not change the trans fluid.

 

[kcdehart]

Even if this 'life time' stuff was good for 100k.
How old is your 2004 T4R now? 14 years...with the same fluid?
Mine was built in '03 its just at 75k now.
Haynes repair manual states 30k or 24 months for trans. 15k if operated in 'severe' conditions.

I know it seems a bit much but that's what the book says.

Not sure who started this myth that you should not change the trans fluid.

I think the myth covers not flushing it. I've heard only to change the fluid in the pan, but not flush it, as flushing will remove the metal that's coming off of the trans that's keeping things viscous. Idk how true that is, but that's what I've heard...

Automatic transmissions are magic to me haha. Give me a manual and I understand it fine.

 

[AuSeeker]

You have a 2004 with a V6 and a 4 speed tranmission not the 5 speed correct?

If so it dosen't use the WS "Lifetime" transmission fluid and should be initially changed at a lower mileage and more often than the initial change at 90,000 miles of the later transmissions, look at your "Maintenance Schedule" book for the proper intervals to change the fluid, the proper transmission fluid is noted on the dipstick and in your owner's manual.

Either way, change the fluid NOW!!

 

[wcjeep]

Were you in 4high or 4low? Curious.

I would flush. Also, consider a cellphone booster. Depending on terrain and your cellphone provider it can add a few miles of coverage.

 

[kcdehart]

You have a 2004 with a V6 and a 4 speed tranmission not the 5 speed correct?

If so it dosen't use the WS "Lifetime" transmission fluid and should be initially changed at a lower mileage and more often than the initial change at 90,000 miles of the later transmissions, look at your "Maintenance Schedule" book for the proper intervals to change the fluid, the proper transmission fluid is noted on the dipstick and in your owner's manual.

Either way, change the fluid NOW!!

Yeah, I'll definitely change it. We pulled the dipstick out and it was brown instead of red and smelled kinda toasty.

Were you in 4high or 4low? Curious.

I would flush. Also, consider a cellphone booster. Depending on terrain and your cellphone provider it can add a few miles of coverage.

I was in 4 high. 4 low probably would've been a good move since I just needed to crawl. Might've saved the torque converter some strain.

I'll look into the cell booster! It sure would be nice...

 

[wcjeep]

I use Weboost cell boosters. Used to be called Wilson Electronics. There are a few factors that affect performance. They are not magic. On average they extend service a few miles. I've had internet access when friends had zero service. The "Sleek" can usually add 18db of signal. They do have a more powerful mobile device that can boost upto 4 devices at 35db each (advertised at 50db). Cost increases. The Sleek is usually enough for most people.

If there is no signal to boost expect no signal. I have found the center of a vehicle hood a great place for the magnet antenna.

 

[ElZilcho]

I was in 4 high. 4 low probably would've been a good move since I just needed to crawl. Might've saved the torque converter some strain.

4lo wouldn't have made any difference. The transmission would have been turning as fast or faster and still wouldn't have been circulating fluid.

 

[kcdehart]

4lo wouldn't have made any difference. The transmission would have been turning as fast or faster and still wouldn't have been circulating fluid.

Yeah, the lack of airflow was what I think really did me in. Moving backwards uphill under a lot of strain really doesn't do wonders for moving air over the trans cooler/rad.

I'm thinking I'm gonna install an external cooler alongside this flush.

 

[ElZilcho]

Yeah, the lack of airflow was what I think really did me in.

I'm sure that was a contributing factor but the root cause is that the transmission doesn't pump ATF through in reverse. The actuators are driven by check valve. When you reverse the output shaft it applies pressure to the "wrong" side of all the check valves for the forward gears to lock them closed so the transmission doesn't accidentally engage a forward gear-set while your driving backwards. When those check valves are closed there is not nearly enough ATF circulating to properly cool the transmission.

Loaded, unloaded, driving, or being towed in reverse long enough will nuke the transmission and it's not unique to 4runners. It happens on pretty much any modern automatic.

Don't ask me how I know this.:doh:

 

[kcdehart]

I'm sure that was a contributing factor but the root cause is that the transmission doesn't pump ATF through in reverse. The actuators are driven by check valve. When you reverse the output shaft it applies pressure to the "wrong" side of all the check valves for the forward gears to lock them closed so the transmission doesn't accidentally engage a forward gear-set while your driving backwards. When those check valves are closed there is not nearly enough ATF circulating to properly cool the transmission.

Loaded, unloaded, driving, or being towed in reverse long enough will nuke the transmission and it's not unique to 4runners. It happens on pretty much any modern automatic.

Don't ask me how I know this.:doh:

That's actually really cool to know. Glad you were able to learn it for me haha.

I guess if I'm ever in a situation like this again I'll reverse a bit, put it in drive /park to let it flow and repeat. Rather than just going at it all at once.