Overheating in Mountains with 3000TC

[ahess77]

OK, I'm in Gatlinburg, TN this week and I was driving through the National Park up the mountains yesterday. Ambient temp was in the mid 90s. It's about 5 to 8 miles up, then back down to Cherokee, NC. Speed limit is 35 mph, so with my 4:10 rear gear I am turning between 2200 and 2700 rpm as you speed up/slow down.

So, after a couple miles of 2500 rpm in 3rd gear my trans temp get upward of 230F (it usually runs 180 to 210 max with the 2nd trans cooler). I know I'm programmed not to lock-up the TC at these slow speeds, so I decide to switch my stock program to see if the normal transmission programming helps the problem. Nope, I shut off the engine, switch to my program #2 (chip with 4 programs, #2 is all stock with 4:10 adjustment only). Trans heats up again and keeps climbing. So, I shift into 2nd to get the RPMs up and get above the stall speed of the TC (it's a PI set to 3000). In 2nd gear I'm turning 2700 to 3500 RPM around all the twisty-turns. Trans temp starts cooling down, but engine starts getting hot, Oil temp is now 230 and climbing. I pop the hood and let it ride on the secondary latch only, but there's only minimal airflow with the huge downstanding flange around the hood.

So, I do this balancing act switching between 2nd and 3rd trying to keep both the oil and trans temps below 250 as I'm climbing to the top at 25 to 35 mph. Anyone else had this problem? Any suggestions on how to keep cool at such low speeds?

I turned around at the top and went back to Gatlinburg so I didn't have to climb up again. Coasted most of the way down in neutral and everything stayed cool.

Let me know if you have any ideas on how to stay cool with these conditions. Thanks.

[Raudermaster]

Do you have a full amount of tranny fluid in there? When was the last time it was changed?

[MercModifier]

Dont be offended, but its possible the fluid is going into the 2nd cooler then back to the factory cooler and then back to the trans.

Just a thought.

[fastblackmerc]

The aux cooler should be plumbed in after the factory cooler.

Factory cooler out to aux cooler in, aux cooler out to tranny.

[ahess77]

The aux cooler should be plumbed in after the factory cooler.

Ok, 2 things, yes the secondary cooler is after the factory cooler and the fluid is redline D4 with about 20k miles.

But, since you asked those questions please provide a technical reason for:

1. Why should the fluid flow through the secondary cooler after the factory cooler if it is a staked plate? Our factory cooler isn't in the radiator so why isn't it just as effective at disapating heat as the secondary cooler?

2. Why would old fluid have any less heat capacity than new fluid and therefore be less effective at cooling? It's not making sluge, so it's flowing just fine. I can see that it may breakdown and not have the same lubracation, but since it's still oil doesn't it still have the same heat capacity when old?

Anybody with some technical info let me know.

Thanks,

[MercModifier]

Ok, 2 things, yes the secondary cooler is after the factory cooler and the fluid is redline D4 with about 20k miles.

But, since you asked those questions please provide a technical reason for:

1. Why should the fluid flow through the secondary cooler after the factory cooler if it is a staked plate? Our factory cooler isn't in the radiator so why isn't it just as effective at disapating heat as the secondary cooler?

2. Why would old fluid have any less heat capacity than new fluid and therefore be less effective at cooling? It's not making sluge, so it's flowing just fine. I can see that it may breakdown and not have the same lubracation, but since it's still oil doesn't it still have the same heat capacity when old?

Anybody with some technical info let me know.

Thanks,

Answer to question 1:
Because the heat of the radiator is passed directly through the stock cooler, basically cooling it with air equivalent to the temp of the coolant, not the ambient air.

[FordNut]

Actually, the OEM cooler is mounted before the radiator. But it is after the AC condenser, so it does pick up heat from that. Plus the heat that is shed by the front cooler passes through the AC condenser then to the OEM tranny cooler.

Which brings to mind, I suppose you tried turning off the AC?

[Stranger in the Black Sedan]

http://www.txchange.com/heatchrt.jpg

Hmm, that is getting toastiieeeeeeee! I would understand a high stall converter heating the trans up below stall speed, it's what they do best. But with the TCC locked it should run cool. Can you feel that your TC is definitely locking up when it is commanded to?

[ahess77]

Actually, the OEM cooler is mounted before the radiator. But it is after the AC condenser, so it does pick up heat from that. Plus the heat that is shed by the front cooler passes through the AC condenser then to the OEM tranny cooler.

Which brings to mind, I suppose you tried turning off the AC?

I'll buy that, my secondary trans cooler is mounted in front of all the other heat exchangers so it should see the coolest air and therefore be able to achieve a lower temperature than the factory cooler after the AC condenser.

AC is also a critical function when it's 95 degrees and humid (heat index of somewhere around 108), so no I didn't turn off the AC.

Lastly, between 25 and 35mph the converter is almost always below the stall speed of 3000 rpm, and because of constant speed changes and braking due to other cars and turns and variation in hill grade the converter is almost never commanded to lock-up under those everchanging power requirements.

What I'm really trying to get to is: will our cars with a high stall torque converter simiply not be able to handle these circumstances? If anyone has programming/driving techniques/cooling tricks other than a larger heat exchanger let me know what you do.

[FordNut]

One thing that comes to mind is the programming. Some of the performance tunes do not allow TCC lockup unless the car is in 4th gear (OD). At the speeds you're describing it would never be in OD. Other tuners allow the TCC lockup feature in 2nd and/or 3rd gear. With TCC locked, there is no TC slippage, so there should be less heat generated.

[ckadiddle]

Was just up there in July for honeymoon. Beautiful area!

[MM_BKK]

One thing that comes to mind is the programming. Some of the performance tunes do not allow TCC lockup unless the car is in 4th gear (OD). At the speeds you're describing it would never be in OD. Other tuners allow the TCC lockup feature in 2nd and/or 3rd gear. With TCC locked, there is no TC slippage, so there should be less heat generated.

Another programming thing to think about is the pesky Converter Lock-Up Tip In. I found this to be VERY annoying. If you're constantly on and off the throttle, the converter is going to unlock and lock constantly. It's probably spending more time unlocked (hence heating up the fluid) with that type of driving where you're constantly changing speed.

There's 2 parameters in the EEC to deal with this:
1st one is Converter lock up delay
2nd one is Converter lock up delay 4th gear

The way it works is, on the 1st one IF your tune has the TC lock up enabled in 2nd & 3rd then you can program a time delay to have TC stay locked when you let up on the throttle until you get back in as long as it's before your programmed time.
On the 2nd one is the same as the 1st one except only when you're in 4th gear.

I programmed my delay time to 15 seconds. My factory tune was set to 0 seconds. You can tell that your delay is 0 seconds by driving to cruising speed so that your TC is locked, then try letting off the throttle and get back into it. If your RPM flare up ~200-300 then settles down then the delay is 0. If the RPM does not flare up then the TC is staying locked. This programming could be done with SCT Pro (I'm guessing). I did mine with Sniper Delta Force.

In theory, if you can keep the car in 3rd gear with the TC locked, your trans should run the coolest because all the planetary gears are locked to one another acting as a solid shaft. In any other gear all the internal trans gears are running against each other thereby producing additional heat.

IMHO, i don't think the heat coming off the AC condenser is going to effect your aux. cooler and factory trans cooler too much. You're probably ahead of everybody else by having the aux cooler. If that was the case, then the engine would be overheating everytime you use your AC following on the theory that the heat from the condenser won't let the engine radiator cool efficientyly enough. In fact, I found that my engine runs a little cooler with the AC on due to the fact that the cooling fan is forced on by the AC.
I believe the main heat source generator is the constant slippage of the TC. If you don't believe me, try power braking to 2800 RPM for 30 seconds and see how fast your trans temp gauge climb. Imagine doing that for 30 minutes.

Hope that will help shed some light.

[ahess77]

There's 2 parameters in the EEC to deal with this:
1st one is Converter lock up delay
2nd one is Converter lock up delay 4th gear


Thanks for all the great info about TC lock-up. This is exactly the info I was asking for. I'll look into how mine's set.

Has anyone been here recently (driven slowly up a 4% grade with twisty turnies) with a 3000 or higher TC? If so, how are your TC lock-up settings?

[1gtx]

Every day I drive up and down Mt. Scott (near Portland OR) going to and from work. The speed limit is 35-40. Up the hill in 2nd/3rd. Down the hill in 2nd in the steep sections (about 2 miles each). If you don't use the low gear going down, you'll eat a set of brakes in very short order.

I have a 3000 stall TC and 4.10s as well as a Reinhart tune. "Stock" performance transmission tune will not work in regular mountain work--especially in hot weather. It has taken a long time of fiddling around with the transmission program to get what I needed. A few basics...

1) lockup in all gears doesn't work--especially for gliding. Lock up kills your ability to glide down hill (does not allow "freewheeling" and causes a lot of unnecessary jerking from harsh shifts/lockups). Also kills the gas mileage "recovery" from eating gas to get up a mountain and not gliding well down the other side.

2) oregon has a basic 55 mph speed limit (lowest west of the rockies). My TC is set to lockup at 57 and unlock at 52 in only 4th gear when using very slight throttle pressure. Standard reinhart and lidio is 65. I've set high throttle angle (foot glued on floor) to not lockup until about 110.

3) locking up a converter only save you about 2-3% on gas mileage in most circumstances. Fine for cruising, useless otherwise.

4) keeping the TC unlocked allows the torque multiplication effect--much greater apparent torque than a stick car at the same rpm (when under the stall speed). Locking up the TC all the time just makes the Marauder act (accelerate and shift) like a 6 cylinder--not exactly the effect that driving a musclecar is suppose to be all about.

5) locking up the TC makes the engine's torque curve the controlling influence and with small V8's there isn't much torque at under 4K (a 4.6L is not the same as a Plymouth 440 [~7.3L/495lbs of torque at 2400rpm--stock] which when going up the rockies out of salt lake city seems to be saying 'hills? I don't see no stinking hills!' :-)

6) Even with my tweaks you need to note when you're going up a hill at a sustained rpm under the stall speed. It's not unusual to find that downshifting a gear only pops up the rpm 100-200rpm. This bring on the torque multiplication effect and dumps the huge potential heat build up in transmission.

Occasionally when going skiing on Mt. Hood (11K+ feet) I find that either increasing or decreasing my speed a few mph can eliminate any heat build up problems when I would otherwise be stuck right at a transition (shift) point.


Hope this helps.

-Mark

[Stranger in the Black Sedan]

I know Lidio's TC lockup is 63, but I thought DR's was lower than that?

[jonroe]

I have Lidio's tune. I know it says lock-up at 63 but I don't see that. When I very slowly and carefully accelerate past 60 I see lock-up no earlier than about 66 or so. I've never seen it lower than 66.