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Auto Trans Temps get HOTTT!!!!

25K views 187 replies 34 participants last post by  YJ-Dog 
#1 ·
So, looking here linky you can see my install on a trans temp gauge. Its been in for about a month now. From what i have found the OEM tow package cooler isn't large enough for trucks that see offroad or towing on back roads. Now these are all summer readings, but thats the time of year we all play. Outside temps ranged from 70-105* for the most part. Around town really depends on ambient, on a cool morning in the 50's I will barely be at 130* when I get to work. But on the same drive in 95* weather it gets to 150-160*. Sitting at a stop light on a 90* day its not uncommon to see 170* or higher. On the hwy when empty driving 75 the trans lives between 160 and 190*. (toyota claims normal operating temps are 122-176). Towing on the interstate (500lbs cargo, 1800lb trailer, 150 lbs tounge weight) the tranny lives at 170* at 55mph and 190-210* at 70mph. On dirt roads it doesnt seem to matter if towing or not, around 180-210* is normal, espically if there is a small hill. Towing up a switchback road the tranny got up to 230*, and that was in 4L to get the rpm's up so the pump was moving more fluid. So all of that is a bit warmer than I want and am already looking at an different cooler that has its own elec fan. But the real kicker was today. I went to a local gravel pit to check on a clunk I have been hearing and decided to play a little. Outside temp was 70*, I put it in 4H and climbed about a 20* hill with some ruts. Well I got playing in the ruts a little and in 30 seconds the temp went from 130 to 190*, and I said wow, hit the top of the hill and got on the pavement.... it only cooled to 160* after 8 miles of 50mph driving (usually keeps the tranny about 130* at 70*).

So if you dont have the aux tranny cooler you REALLY need one. If you have the tow package and tow you need another cooler. If you wheel your truck you need another cooler.

I think the biggest issue is Toyota put the aux cooler directly behind the bumper, gets zero direct airflow. I went on two test drives the other day and proved that the bumper blocks way too much air. The first lap on the test I had the bumper on and saw about 160*, and once I set cruise it didnt drop below 140*, and took a few miles to get there. With the bumper removed I went on another drive, drove slower and harder, and the highest temp was 145*, and as soon as I hit cruise it dropped to 120* w/in about 30 seconds. So the location of the aux cooler is not conducive to slow speed driving, especially when towing or wheeling.

I am running stock size tires, and don't have too much extra weight on the truck.
 
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#6 ·
Fluid doesnt last as long... which toyota claims is life time fluid, or 60K if you tow. I will probably change mine at 30K.. Sure, takes more power to turn everything than just 1 axle.

and that was a buying point to get the tow package, fu toyota, got us again
Well think how bad it would be if you didnt have the tow package.. And the extra oil cooler and 130 amp alt are nice.... There isnt a rig out there that has adequate tranny cooling for backroads towing or real 4wd use... they are all designed for highway use.
 
#7 ·
I have had my oil temp go into the red on on two occasions while climbing a steep hill in 4 Lo. I always thought it was the tranny getting hot, I do not think the aux cooler gets sufficient airflow and don't think it is big enough for anything other than light towing on flat ground.
 
#11 ·
Where is your oil temp mounted?

I've noticed similar temp readings on my trans. temp gauge. I have not thought much about it in comparison to my GMC that has an Allison trans. It will run right about 200 all the time no matter what the outside temperature is and whether towing or not. I know its an apples & orange comparison, but is ~200 really going to effect the long term longevity(sp?) if the oil is changed at routine intervals?
If you change the fluid reg no, but remember the sensor is probably in the pan on the Alison so that means you could be seing temps 30-60* higher at the hottest fluid.

I dont know what all is in the 30k service but I planed on doing it every 30K anyway, if I still have my "truck" then.

The only truck that is made for 4x4 use is a Jeep. I'll probably trade this truck in for the new JT when it comes out.
Shit, Jeeps aren't really built to wheel... you cant even climb an incline with their auto trans w/out replacing the trans oil pan for a deeper one with a differnt sump as the OEM one sucks dry.. .that and you'll break your OEM axles with OEM size tires on a Jeep.... .They are built for show, just like most rigs.

Maybe a small e-fan on the cooler?
Yeah, but its only the size of a envelope. So I think an aftermarket cooler with an efan is the best, they are built to work together.
 
#8 ·
I've noticed similar temp readings on my trans. temp gauge. I have not thought much about it in comparison to my GMC that has an Allison trans. It will run right about 200 all the time no matter what the outside temperature is and whether towing or not. I know its an apples & orange comparison, but is ~200 really going to effect the long term longevity(sp?) if the oil is changed at routine intervals?
 
#14 ·
im running 2 aux coolers on my 00, i bypassed the stock cooler in the radiator. one aux cooler has a e-fan on it, it helps a lot when going slower.

here are my 2 coolers, the bottom one has the fan:

http://www.importperformancetrans.com/coolers.shtml#main

Long Tru- Cool LPD Transmission Cooler- 22,000 GVW (4490)
Long Tru- Cool LPD Transmission Cooler- 28,000 GVW (4590)

temp is taken on the rubber line coming from the trans before any coolers

my temp on the highway sits right at 180 if the torque converter is locked, as soon as it unlocks temp goes up to 200-210 and holds there. as soon as it locks again it drops back down to 180.

climing hills it rises to about 230 or 40 depending on how hard i'm on it.

im going to look into one or two of these eventually
 
#28 ·
Why bypass the stock cooler? My TRD cooler is hooked up after the stock cooler. I towed between 3500-4000 lbs 1500 miles and the highest it ever got was 215 in second gear since going up really steep grades and in flat roads in third gear 170.
 
#15 ·
Wow for all that cooling thats REALLY hot... I would think I have less cooling, but I dont seem to run that hot.

Are you running synthetic fluid?
 
#24 ·
Thats way too hot. Thats sucks. My old ford stayed at 160 degrees all day long. Hit 205 max towing a heavy trailer on the backroads at 10 mph. This tells me that the stock cooler on the towing package sucks. There is no way you are going to get 100k out of this tranny if you tow and hit these temps.

Curious, on the highway towing, what happens to the temp if you keep it in "4" instead of "D". That would keep it out of overdrive at least for highway towing on the hills. I notice towing my boat that if there is any incline at all the rpm jumps up slightly which I assume is just unlocking the T/C but still keeping it in overdrive. If I keep it in 4 the T/C should stay locked and run cooler?

Now I can see I really need a temp gage, hope the new scangage comes out soon.
 
#36 ·
IMO, the round tube style coolers don't work as well as the Multi row flat tube style coolers (Earl's performance,and Setrab). I also agree with John (AH64ID) that the cooler doesn't see anywhere near enough airflow to satisfy the cooling requirements under heavy towing conditions. Also, when you are running trails, the converter is not locking up, so the converter is creating a lot more heat than under normal cruising conditions. I'm kinda concerned with John's findings of high temps at slow speeds. Damn, guess I'm gonna have to look into spending a few hundy on a new trans cooler...thanks John:) Also, this is not a "Toyota only" problem. All of the major auto mfrs. come up short when it comes to trans cooling. Example: Why in the hell would anyone want to run the primary trans cooler in the radiator??? Hum, let's see, I think I'll run the trans fluid next to another fluid that is averaging 220 degrees...that's smart. Now if I understand just the basics of thermal dynamics, that means that the cooler fluid will absorb heat from the higher temp fluid, now that's rocket science:rolleyes: All in the name of saving a few bucks per unit. Go figure.
 
#39 ·
If I'm understanding this right the trans fluid cooler on tow package equipped trucks is located behind the bumper, and the school of thought here is that its not getting enough airflow thru the cooler to be effective. So to me the simple fix would be to move the cooler up higher, say behind the grill, so you would get the maximum airflow.

hokihigh
 
#40 ·
You could, but then you still have the issue of little to no airflow when driving slow.. i.e. wheeling or backroads towing.. so you dont fix that issue, but you do help when towing on the hwy... So the best thing would be a different cooler with an attached fan, mount it in the airflow for the hwy, and the fan takes care of the airflow on the trail...
 
#44 ·
Well after further thought on why Toyota would put the cooler behind the bumper like that, I don't think it was a mistake. I believe they put it there as a compromise, meaning in the winter time if the cooler was up higher, it would not allow the trans to get to optimum working temperature. So I think the positioning was a compromise on their part to try and get the optimum temp for the trans in all conditions, not just hot.

With that said it still gets too hot in some circumstances such as wheeling and towing. Which 95% of the people that own these trucks don't do.
I still feel something has to be done since I'm in the 5% that actually uses their trucks for everything, not just mall crawling. So I think I'm going to go with the smaller version (which still might be too big) that ah64id posted a pic of even though the bigger one is only $20 more. The smaller one won't be exposed as much as the bigger one and in the hot summer it will have the fan. Thoughts?

bigger one:
http://store.summitracing.com/partd...t=BMM-70297&N=700+4294854215+115&autoview=sku

smaller one:
http://store.summitracing.com/partd...t=BMM-70298&N=700+4294854215+115&autoview=sku

An here is a list of all the fan/coolers Summit has:
http://store.summitracing.com/egnsearch.asp?N=700+115+4294854215
 
#46 ·
I am thinking about the bigger on in the OEM location.. it will allow it to warm up some in winter and the fan will keep it cool in summer... if need be I can unplug the fan and cover it with cardboard... but the radiator will help it warm up to at least 130*ish....
 
#57 ·
wait a second, im confused, when towing on the highway, is it better to stay in D or in 4? im just goin by what the manual says, and i just got done towing my boat on a 1000 mile trip that was always in 4, so im just making sure i diddn't just toast up my tranny. im considering about getting a bigger boat now, which will then lead to a bigger concern on the tranny being cool. has anyone tried bringing this up to a toyota dealership and see what there take on it is, if its ok to installl an aux tranny cooler without voiding waranty. just curious because now i wouldn't even consider towing 5500lb's with it.
 
#58 ·
I don't believe that you could possibly void your warrantee by adding an aux cooler. Unless you didn't top off the trans fluid or messed up the install somehow.:2cents:
 
#61 ·
Silver: the best way is to get with some local wheelers and learn the ropes. I got into racing at 16 years old just by hanging out with some racers at the local burger joint. I built my first engine at 17 and never looked back. I started fabbing stuff in my early 20's when I put a 73 camaro on a blazer chassis and the rest is history. You can do anything you set your mind to. Good luck.:)
 
#78 ·
The stealeship is pullin your johnson, or they aren't doing a complete flush. Those bastards are charging any where from $15-20 per qt for this stuff. Makes you want to go full synthetic at your first real flush. That alone would save you a ton of cash.:2cents:
 
#79 ·
Hmm... I still didnt think it was that much for the fluid? And I thought that OEM spec WS is a full syn?? Oh well I've got 20K to figure it out.
 
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