Aisin-transmission too hot warning

[getpower1]

Hi all,

Trying to figure out a problem with my truck. 2018 Crew Cab Long Bed 4x4 3500 SRW that I bought new in 2018. Has the HO Cummins with the Aisin. Truck currently has around 43,000 miles on it. Way more driving empty than towing, but since the very end of 2020 we’ve had a three axle toy hauler that weighs probably around 14,000lbs. Never have had it on a scale but I’m very familiar with weights.

Up until a recent trip, the highest I have ever seen the trans temp get is around 168 degrees. Monitor gauges pretty constantly. Now on the recent trip we were about to pull up the steep long hill to our house (just an in town road where we live),something I’ve done many times before with no issue, and I locked the trans to 2nd gear at the stop sign at the bottom of the hill at the stop sign before the climb (not sure if I’ve done this before), then proceeded up the hill.

About half way up the transmission started to get clunky and then I got a warning that the transmission temperature was too hot. I looked at the guages and it was reading at like 180 or 188 or somewhere in between. Don’t remember which, but I remember it wasn’t into the 190s.

I stopped, put the truck in 4lo, got up to my house, got out, opened the gates with the truck in park. Temp at that time was 179. Got everything situated for a couple minutes, kids etc…, got back in, temp still at 179. Backed the trailer in, have the truck a couple minutes and shut down, still trans at 179.

Unloaded the camper, got back in the truck to back the rest of the way in and unhook and temp had cooled back off to the low 160s. Total mileage for the trip there and back was just above 200 miles and didn’t have a temp problem till the hill when home.

Since then, I’ve done a drain and fill on the trans fluid. Which was my first drain and fill. Didn’t consider my use of the truck “heavy” so I’ve had the fluid in the garage since around 30k miles, but it hasn’t been a priority.

After the drain and fill I took the truck on a lengthy empty test drive and it took quite a long time for the trans to even get past 159 degrees. By the time I hit that same hill to home it was 163 when pulling up to the house. Thought my problem was solved!

Now, we recently took a trip from around SF area where we live up to Reno. This was pretty much the next time the truck has been used since the trip before the drain and fill. When going through the traffic going through SF empty not towing, the trans temperatures got up to 177 degrees. Once we got back up to freeway speeds it came right back down again. Seemed fine for the rest of the trip, but now I’m freaking out because it’s not what I would call normal behavior for my truck.

I understand those temps are well within normal and no harm should have been done to the transmission. It shifts perfectly fine, just as it did before the problem happened.

Only differences between the last trip we pulled the fifth wheel and the one where it had the problem was a banks monster ram was installed, and I went from 275/18 tires to 285/18 tires. Otherwise truck is all stock. I understand gearing and things like that and I don’t believe that a tire size difference would cause a transmission to do what I’m describing. Even sitting in traffic before and just getting on and off the brake pedal wouldn’t make the temp go past 168. No acceleration, this is happening now. Not to mention the drive of over 100 miles there and most of the way back with zero temperature problems. Every time I looked down I was in the 160s range.

Any ideas? Coolant bypass valve messed up? The symptom of not getting up to temp on the test drive after may show this to be the problem?

 

[AH64ID]

Sounds like you were in 2nd gear with the torque converter unlocked so the temps rose quickly. Try the climb in 1st gear, as suggested by the owners manual, for cooler temps. I’ve found 1st does a much better job at keeping the temps down when the torque converter is unlocked on long slow climbs.

The warning light is based on the TC outlet temp, which is generally always hotter than the sump temp that’s displayed on the dash. The warning comes on at 293°F from what I’ve read.

As far as the fluid change Ram doesn’t have a different service interval for the Aisin based on use, it’s 30K or 2 years for a fluid change and 60K or 4 years for a fluid/filter change. That’s definitely a bit conservative, even for the non-synthetic fluid, but that’s how they rate it.

 

[gimmie11s]

Yeah, I'd say 6 years for your first fluid change is excessive. IMO I seriously doubt you hurt the trans by extending the interval, but non-synthetic oils do degrade MUCH faster than synthetics.

The only time ive seen my trans get hotter than 180 is a similar climb to what you describe. Roads were shut down to one lane on a 6% grade, towing my toy box fully loaded. Truck was hunting between 1st and 2nd gear the whole climb and I saw 190* on the dash. Did not get any warning lights however, and it still shifted fine.

 

[getpower1]

Sounds like you were in 2nd gear with the torque converter unlocked so the temps rose quickly. Try the climb in 1st gear, as suggested by the owners manual, for cooler temps. I’ve found 1st does a much better job at keeping the temps down when the torque converter is unlocked on long slow climbs.

The warning light is based on the TC outlet temp, which is generally always hotter than the sump temp that’s displayed on the dash. The warning comes on at 293°F from what I’ve read.

As far as the fluid change Ram doesn’t have a different service interval for the Aisin based on use, it’s 30K or 2 years for a fluid change and 60K or 4 years for a fluid/filter change. That’s definitely a bit conservative, even for the non-synthetic fluid, but that’s how they rate it.

Helpful information to know. I’ll have to see if I can do some research on the outlet temperature and the warning it gave me.

It’s a fair point about the use case. Again, just not a priority. Fluids checked every time I use the truck and things always have looked good and still do. Not saying my lack of service is the right thing to do. But I’ve seen worse.

I don’t see that I’ve done any damage and it doesn’t act like it. Haven’t towed since then yet though. Maybe I should pull the trailer out and go on a quick highway run with it.

Again, I feel like something is off with the temperatures fluctuating. They have always been really solid on the readout. The fluctuation in traffic and then when on the highway is new. I’m well aware of how cooling works. But It’s never been as drastic on the readout as it is now.

Also, I think you’re correct about the torque converter not locking and slipping. But I don’t see why it didn’t lock. I was steady on the throttle and everything felt fine. Just didn’t seem to be doing what I thought it should be doing.

 

[H3LZSN1P3R]

Helpful information to know. I’ll have to see if I can do some research on the outlet temperature and the warning it gave me.

It’s a fair point about the use case. Again, just not a priority. Fluids checked every time I use the truck and things always have looked good and still do. Not saying my lack of service is the right thing to do. But I’ve seen worse.

I don’t see that I’ve done any damage and it doesn’t act like it. Haven’t towed since then yet though. Maybe I should pull the trailer out and go on a quick highway run with it.

Again, I feel like something is off with the temperatures fluctuating. They have always been really solid on the readout. The fluctuation in traffic and then when on the highway is new. I’m well aware of how cooling works. But It’s never been as drastic on the readout as it is now.

Also, I think you’re correct about the torque converter not locking and slipping. But I don’t see why it didn’t lock. I was steady on the throttle and everything felt fine. Just didn’t seem to be doing what I thought it should be doing.

I don’t think the aisin locks in 2nd at all.

As far as temps you did nothing that would cause damage as that starts to occur at about 250-270°F

 

[AH64ID]

It’s a fair point about the use case. Again, just not a priority. Fluids checked every time I use the truck and things always have looked good and still do. Not saying my lack of service is the right thing to do. But I’ve seen worse.

You can't go off how a fluid looks to determine if it's good or bad.

Again, I feel like something is off with the temperatures fluctuating. They have always been really solid on the readout. The fluctuation in traffic and then when on the highway is new. I’m well aware of how cooling works. But It’s never been as drastic on the readout as it is now.

It sounds normal for how you're describing how you use the truck.

Also, I think you’re correct about the torque converter not locking and slipping. But I don’t see why it didn’t lock. I was steady on the throttle and everything felt fine. Just didn’t seem to be doing what I thought it should be doing.

I don’t think the aisin locks in 2nd at all.

The Aisin will lock in 2nd but not until ~20 mph. It will hold the TC locked down to about 18.

 

[Brutal_HO]

You can't go off how a fluid looks to determine if it's good or bad.


It sounds normal for how you're describing how you use the truck.





The Aisin will lock in 2nd but not until ~20 mph. It will hold the TC locked down to about 18.

Assuming it's holding TC locked during active EB, mine holds down to 900RPM - around 11-12 MPH.

 

[AH64ID]

Assuming it's holding TC locked during active EB, mine holds down to 900RPM - around 11-12 MPH.

Yeah 900 will be 12 mph, but they unlock as soon as you apply throttle.

 

[getpower1]

For sure I wasn’t doing 20 mph. So there’s my definite answer on what happened and why. I’ve had the exhaust brake working going down the same hill several times. Can’t recall how fast I was going but I’d have to say it’s somewhere around 15mph. Definitely not 20. Had to have tow haul activated to get it to do it.

I’ve got a new approach on how I deal with this hill from now on, that’s for sure. Had to have been changed gearing with the new tires. Would’ve been nice if 4.10s were offered with the SRW trucks.

I still don’t think the temperature fluctuation is normal for the truck, though I understand they’re within safe levels, but I’ll have to run it and see what happens long term. Have no other choice really. I think it’s unlikely but it could be one of those things that’s always happened this way and I’ve just noticed it because I had a problem and was monitoring more than normal. Again, I think that’s unlikely.

Thanks for the insight.

 

[Brutal_HO]

I wonder if CP or the other guy that's doing Aisin tunes can get them to lock up at lower speed. One would think if they cracked them, they should be able to do that and even lock them in 1st gear down to xx MPH/RPM?

 

[AH64ID]

I noticed on my way to work today I can keep the TC locked in 2nd below 18 mph, but that was empty on a flat road. On a hill it always seems to unlock at those parameters.

Locked in 1st would be sweet, or even at 15 in 2nd.

On long slow pulls if I’m able to hold 20 I’ll let it lock in 2nd and use CC to keep it right at 20, but often those long slow pulls have too many tight corners.

 

[H3LZSN1P3R]

I wonder if CP or the other guy that's doing Aisin tunes can get them to lock up at lower speed. One would think if they cracked them, they should be able to do that and even lock them in 1st gear down to xx MPH/RPM?

I believe I saw somewhere PPEI had some tunes with locked shifts but even the unlocked shift ones were still locked at lower speeds for better EB and temps

I know with the 68RFE the locked shifts was a game changer the trans runs much cooler and shifts better with better EB use coupled with higher shift points it really changes the truck

 

[getpower1]

In all honesty I’m probably a good use case for the 2lo bd modification. I just got the bd bypass valve delete in the mail today because I ordered it before posting here. I’m going to do way more research on that before installing though because I’m not sure that’s a real problem.

If I tune it’s going to be for weight loss. So I’d have to hold off for trans stuff for now because of money. Unless the thing granades. But after a 300 plus mile trip empty I think it’s fine.

 

[AH64ID]

In all honesty I’m probably a good use case for the 2lo bd modification. I just got the bd bypass valve delete in the mail today because I ordered it before posting here. I’m going to do way more research on that before installing though because I’m not sure that’s a real problem.

If I tune it’s going to be for weight loss. So I’d have to hold off for trans stuff for now because of money. Unless the thing granades. But after a 300 plus mile trip empty I think it’s fine.

I have the 2Lo kit and unfortunately the TC still won’t lock below 20 mph, but you can get the rpms higher.

If you had a thermostat problem you would see high temps more often, and the pan temp would have been much higher too.

I know you don’t think so, but it all does seem normal for what you were doing. I monitor TC outlet temp on my CTS3 and loaded up a grade in 2nd at less than 20 mph and the temp climbs fast, very fast and much faster than the pan temp.

 

[H3LZSN1P3R]

If I tune it’s going to be for weight loss. So I’d have to hold off for trans stuff for now because of money. Unless the thing granades. But after a 300 plus mile trip empty I think it’s fine.

Deleting is better with trans tuning for trans life and for the added benefits trans tuning offers. Thankfully with the Aisin being a standalone TCM you can have one company for the engine weight loss side of things and the 2 companies that to have Aisin tuning but not deletes you can just use them for the trans tuning.

 

[getpower1]

I have the 2Lo kit and unfortunately the TC still won’t lock below 20 mph, but you can get the rpms higher.

If you had a thermostat problem you would see high temps more often, and the pan temp would have been much higher too.

I know you don’t think so, but it all does seem normal for what you were doing. I monitor TC outlet temp on my CTS3 and loaded up a grade in 2nd at less than 20 mph and the temp climbs fast, very fast and much faster than the pan temp.

No I didn’t figure it would make the torque converter lock. I was more speaking to the fact that it’ll make climbing my hill easier on the truck.

The CTS3 comment is actually very helpful. Thank you.

 

[getpower1]

Deleting is better with trans tuning for trans life and for the added benefits trans tuning offers. Thankfully with the Aisin being a standalone TCM you can have one company for the engine weight loss side of things and the 2 companies that to have Aisin tuning but not deletes you can just use them for the trans tuning.

Thanks. I’ve been out of the diesel game for a long time as far as research and what’s going on. I bought the truck new, well informed with years of knowledge and many other diesel trucks and then life has happened and being a diesel truck guy and staying informed has gone by the wayside.

 

[MEGA HO]

...
and I went from 275/18 tires to 285/18 tires.
...

This says nothing about the tire height. This is metric and only part of the measurement.
285/75R18 for example, the 1st number is the tire width in mm, the 2nd number is sidewall height, 75% of 285 in this case 213.75mm, the R18 obviously is the rim size.
To get the tire height you take sidewall height x2 plus the rim size, so in my this example the tire is 34.8". Your numbers don't tell us anything.

Sidenote: I think US lives in the stone age using imperial system but the the tire size is the only place where it actually makes sense.

 

[flan]

Sidenote: I think US lives in the stone age using the logical system but the the tire size is the only place where it actually makes sense.

Fixed it for ya

 

[Brutal_HO]

This says nothing about the tire height. This is metric and only part of the measurement.
285/75R18 for example, the 1st number is the tire width in mm, the 2nd number is sidewall height, 75% of 285 in this case 213.75mm, the R18 obviously is the rim size.
To get the tire height you take sidewall height x2 plus the rim size, so in my this example the tire is 34.8". Your numbers don't tell us anything.

Sidenote: I think US lives in the stone age using imperial system but the the tire size is the only place where it actually makes sense.

LOL, What drive size are all your ratchets?

Don't worry, soon you'll be the 51st state and we can kick that metric system to the curb (I keed of course).