Trans. Temp
- Thread starter JBM
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Mine gets 125-150 on the freeway in the summer, secondary tranny cooler inline with stock cooler and redline D4 synthetic atf. Ive got an idiot light so if i dont see it comming on i must be ok. What its set at i dont know.
I like to see 100-150F. My PSD pickup runs 115-125F in the sump all year. 200 is too hot if it's sustained, getting 200 while racing up a hill isn't a big deal as long as the temp comes down. I'd put an aux cooler with a oilstat on your rig, it's a lot less expensive than a rebuild!
Patrick
Patrick
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Sure, but where is it being grabbed from? On cross flows it runs on the outlet side tank (usually = unless you've got an oil cooler on one side and a trans cooler on the other tank). It will shed heat to the cooler end of the trip through the rad. If it's a vertical flow rad, the tank is at the bottom and the rad has shed all the heat that it can. I don't know the delta (it would depend on a lot of factors), but it's probably a good bit cooler, in all instances, then the thermostat setting for the engine (assuming the rad has enough capacity in all circumstances).
Gary writes:
I believe that most cars with automatic transmissions in the milder regions of North America probably could benefit from an auxiliary tranny cooler. In the cold states like Minnesota, it might be better to cover or bypass the cooler in the wintertime.
I concur. I've measured this on several cars, and the difference between the temp at the upper radiator hose and the lower radiator hose was about 30 to 40 degrees. As I recall the figures for my Taurus (without A/C or A/C condenser to obstruct the radiator), the radiator outlet temp on a hot summer day was about 156 degrees Fahrenheit. Also in the summer I run about 1/3 glycol coolant, and 2/3 distilled water. Of course, air flow, traffic conditions, engine load, etc. etc. have to be considered.
I believe that most cars with automatic transmissions in the milder regions of North America probably could benefit from an auxiliary tranny cooler. In the cold states like Minnesota, it might be better to cover or bypass the cooler in the wintertime.
One issue not considered thus far in the discussion is where the trans oil temp is measured. Some advocate measuring the oil in the pan, others the return oil from the cooler and a few the oil out to the cooler. I had a rig with a three way switch and three senders, one each in the pan, the oil line to the cooler and the return oil line.
The actual temps at each position will vary somewhat according to the tranny. Some automatics run hotter by nature than others and vice versa. In my case, the trans was the notorious GM 700R4... known for being a hottie among other things. Ahem!
With the stock vehicle on an 85 degree ambient day at slow speeds in mild four-wheeling situations with the converter unlocked, while pan temp was 190, the outflowing oil was 250+ (gauge pegged), the oil coming out of the factory radiator cooler) was about 200. Similar conditions were experienced when climbing Vail Pass in Colorado with the converter unlocked (I had a "kill" switch to lock out the converter lockup).
I learned that watching the outgoing oil tended to induce heart failure because this oil has been superheated by the torque converter on a 700R4, which has a "slippery" converter. The torque converter is the major heat producing element and the relatively loose lockup converters of today (loose until lockup that is) result in hotter temps generally than the old three speed non-lockup converters of days gone by that had lower stall speeds.
You do not want to know what the temps were on hot days in harder four-wheeling with the stock rig. I twice had the "cherry volcanos" out the dipstick with the gauge pegged in all positions.
Cruising down the freeway in converter lockup at 70 ambient yielded completely different numbers, about 190 to the cooler, 130 out of the cooler and 145 in the pan.
In town, stop and go, at 70 ambient, 195-200 to the cooler, 170 out and 160 in the pan.
In some cases, downhills mainly, the cooler outflow oil was hotter than the inflow.
In my case, an '83 diesel Blazer, I found that the OE radiator cooler could usually pull 40-50 degrees off the oil temp.
When I added an oil to air cooler, it could knock off another 30-100 degrees depending on ambient temp. With that cooler in a Colorado winter I had overcooling problems in normal easy driving. I had the oil-to-air cooler routed after the radiator, so on a 30 degree day the oil in the trans barely warmed up. I rigged it so I could switch the lines and route the air cooler BEFORE the radiator cooler. This was in the '90s and that neat oil thermostat deal was temporaily out of production.
A deep pan knocked another 5-15 degrees off (depending on ambient) in just about every situation.
A shift kit helped a little in town but it was a hard-to-measure blip in the readings. I later had a tighter converter installed, but didn't really test it much. I did note a drop in temp, though.
A big oil-to-air cooler was the answer but it's effectiveness varied according to ambient temp and somewhat to humidity. On humid days, it didn't seem as effective.
The biggest help was going to lower gears. The truck had 3.08s. Temps jumped when I installed 31 inch tires with these gears, but dropped significantly when I swapped in 4.10s. They went back up when I installed 35 inch tires and even higher when I went to 37s, still with 4.10s. They dropped down again when I installed 4.88s. The more you slip the converter, and keep the trans out of lockup, the more heat. Lessen the load with lower gears and you run cooler.
So, your ultimate temp will depend on where you measure it, what tranny you have and your rigs genreal weight and gearing situation. If you have a 700R4 with 200 degrees in the pan, you've got 250+ going to the cooler. Do you want fries with that?
Where to put the sender? Either the pan or the return line, IMO.
To contrast, I have an '86 F-250 6.9L diesel that primarily has been a tow rig. I have a sender in the pan of the C-6 (generally noted a a cool tranny). With a moderately large air-to-oil cooler, it runs 145 on an 80 degree day in town and less on the higway (bottom number is 140 on the gauge). Towing at 18,000 CGVWR it never has broken 200 in the pan.
The actual temps at each position will vary somewhat according to the tranny. Some automatics run hotter by nature than others and vice versa. In my case, the trans was the notorious GM 700R4... known for being a hottie among other things. Ahem!
With the stock vehicle on an 85 degree ambient day at slow speeds in mild four-wheeling situations with the converter unlocked, while pan temp was 190, the outflowing oil was 250+ (gauge pegged), the oil coming out of the factory radiator cooler) was about 200. Similar conditions were experienced when climbing Vail Pass in Colorado with the converter unlocked (I had a "kill" switch to lock out the converter lockup).
I learned that watching the outgoing oil tended to induce heart failure because this oil has been superheated by the torque converter on a 700R4, which has a "slippery" converter. The torque converter is the major heat producing element and the relatively loose lockup converters of today (loose until lockup that is) result in hotter temps generally than the old three speed non-lockup converters of days gone by that had lower stall speeds.
You do not want to know what the temps were on hot days in harder four-wheeling with the stock rig. I twice had the "cherry volcanos" out the dipstick with the gauge pegged in all positions.
Cruising down the freeway in converter lockup at 70 ambient yielded completely different numbers, about 190 to the cooler, 130 out of the cooler and 145 in the pan.
In town, stop and go, at 70 ambient, 195-200 to the cooler, 170 out and 160 in the pan.
In some cases, downhills mainly, the cooler outflow oil was hotter than the inflow.
In my case, an '83 diesel Blazer, I found that the OE radiator cooler could usually pull 40-50 degrees off the oil temp.
When I added an oil to air cooler, it could knock off another 30-100 degrees depending on ambient temp. With that cooler in a Colorado winter I had overcooling problems in normal easy driving. I had the oil-to-air cooler routed after the radiator, so on a 30 degree day the oil in the trans barely warmed up. I rigged it so I could switch the lines and route the air cooler BEFORE the radiator cooler. This was in the '90s and that neat oil thermostat deal was temporaily out of production.
A deep pan knocked another 5-15 degrees off (depending on ambient) in just about every situation.
A shift kit helped a little in town but it was a hard-to-measure blip in the readings. I later had a tighter converter installed, but didn't really test it much. I did note a drop in temp, though.
A big oil-to-air cooler was the answer but it's effectiveness varied according to ambient temp and somewhat to humidity. On humid days, it didn't seem as effective.
The biggest help was going to lower gears. The truck had 3.08s. Temps jumped when I installed 31 inch tires with these gears, but dropped significantly when I swapped in 4.10s. They went back up when I installed 35 inch tires and even higher when I went to 37s, still with 4.10s. They dropped down again when I installed 4.88s. The more you slip the converter, and keep the trans out of lockup, the more heat. Lessen the load with lower gears and you run cooler.
So, your ultimate temp will depend on where you measure it, what tranny you have and your rigs genreal weight and gearing situation. If you have a 700R4 with 200 degrees in the pan, you've got 250+ going to the cooler. Do you want fries with that?
Where to put the sender? Either the pan or the return line, IMO.
To contrast, I have an '86 F-250 6.9L diesel that primarily has been a tow rig. I have a sender in the pan of the C-6 (generally noted a a cool tranny). With a moderately large air-to-oil cooler, it runs 145 on an 80 degree day in town and less on the higway (bottom number is 140 on the gauge). Towing at 18,000 CGVWR it never has broken 200 in the pan.
Jim Allen, Wow............Got Photos ????
I still have a few, but it's been nearly 10 years since I did all that testing. Most of this went into either "4x4 Performance" magazine (Big Blazer Buildup starting in Sept '97) or "Four Wheeler" magazine (Project Blazer parts 1-10, '98-2000).
The pics would not too interesting in the context of this discussion anyway. I did a pretty scabby job of welding the bung in the pan and would rather not have you see it!
Plus,one inline fitting looks pretty much the same as another.
It's the info that provides the most useful material. And remember, unless you have an identical vehicle, it will only provide you with useful trends, not absolutes.
You can still buy the inline fittings from B&M, and other places. I just bought some weld-in bungs from AutoMeter to install a rear axle temp gauge in my old Ford and it could be applied to a tranny pan. One thing I would like to see now is the effect synthetic ATF might have on trans temps. In my testing thus far, synthetic oil in the diff made a significant drop.
BTW, in revieiwing my post, I realized I mixed up two numbers:
The pics would not too interesting in the context of this discussion anyway. I did a pretty scabby job of welding the bung in the pan and would rather not have you see it!
It's the info that provides the most useful material. And remember, unless you have an identical vehicle, it will only provide you with useful trends, not absolutes.
You can still buy the inline fittings from B&M, and other places. I just bought some weld-in bungs from AutoMeter to install a rear axle temp gauge in my old Ford and it could be applied to a tranny pan. One thing I would like to see now is the effect synthetic ATF might have on trans temps. In my testing thus far, synthetic oil in the diff made a significant drop.
BTW, in revieiwing my post, I realized I mixed up two numbers:
Exchange the 190 with the 200 above
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Go to ebay. Hit ebay motors ..parts and accessories ..put "cooler" into the search engine (make sure you're at least in ebay motors). TONS of them ..cheap. New ..used..plate ..tube ..what have you
This may be a little off-topic, but I have a rant about in tank rad ATF/Oil coolers. As far as ATF is concerned, it seems that the rad cooler is defeating the purpose somewhat. I don't want to heat up (need to know engine coolant temp, but I usually assume 180F average) my ATF to 150+ degrees (obviously depending on rad type and efficiency) before I start to load the transmission. Also, I have seen numerous in tank coolers fail and load the ATF with coolant - and it takes an amazingly small amount of coolant to kill the trans (in some cases a couple ounces). I have run stainless stacked plate oil to coolant exchangers (the type that would be found on many Detroit Diesels for decades) with much better success; however it is a much more involved process to retrofit these in place of the rad coolers, impossible in some cases.
I have two trucks that I put the largest coolers with high flow fans under the bed of the truck and eliminate the ATF in the rad altogether. I used an oilstat to help warm the ATF to about 100F before any meaningful cooling takes place (oilstat does allow a small bypass to prevent a “cold shock”). Under most conditions the large coolers kept up with BTU input without the fan. In my oldest truck I had to run the fan quite a lot, so I have two coolers in series and almost never run the fan now.
Newest truck is a PSD with the 4r100. I have a re-valved accumulator valve body and a low stall BD converter with an always locked TC after 25 mph. This truck is usually 17,500 to 21,250 GCVW. ATF to cooler around 175F, from cooler 100F, sump is 125F (with the fans off, only need them on in hot ambient temps usually). Remember that not all the ATF is sent through the cooling circuit. In most cases HDD automatics send 30% to the cooler, the rest back to the sump. This is a poor example since the converter stays locked up most of the time. My 77 GMC with the TH400 gets quite hot when towing the same load (don’t use it now that I have the diesel, spend much less money on broken rods and cranks). The 77 sees about 218 to the cooler, 160 from the cooler, about 178 from the sump. Problem with the 77 is since it’s a no lockup TC, it builds a lot more heat when pulling hard. Although after I top the hill the temp would go down to about 218 to the cooler fairly quickly.
Jim Allen, I went through the back issues of Four Wheel and checked out the articles (missed about 3 out of the 10) nice articles. I have a similar vintage GMC that I put a 453 Detroit into (probably made about the same power as the 6.2, but sounded way better). If any of you are still a wake, I’m finally done
(sorry for hijacking the tread)
Patrick
I have two trucks that I put the largest coolers with high flow fans under the bed of the truck and eliminate the ATF in the rad altogether. I used an oilstat to help warm the ATF to about 100F before any meaningful cooling takes place (oilstat does allow a small bypass to prevent a “cold shock”). Under most conditions the large coolers kept up with BTU input without the fan. In my oldest truck I had to run the fan quite a lot, so I have two coolers in series and almost never run the fan now.
Newest truck is a PSD with the 4r100. I have a re-valved accumulator valve body and a low stall BD converter with an always locked TC after 25 mph. This truck is usually 17,500 to 21,250 GCVW. ATF to cooler around 175F, from cooler 100F, sump is 125F (with the fans off, only need them on in hot ambient temps usually). Remember that not all the ATF is sent through the cooling circuit. In most cases HDD automatics send 30% to the cooler, the rest back to the sump. This is a poor example since the converter stays locked up most of the time. My 77 GMC with the TH400 gets quite hot when towing the same load (don’t use it now that I have the diesel, spend much less money on broken rods and cranks). The 77 sees about 218 to the cooler, 160 from the cooler, about 178 from the sump. Problem with the 77 is since it’s a no lockup TC, it builds a lot more heat when pulling hard. Although after I top the hill the temp would go down to about 218 to the cooler fairly quickly.
Jim Allen, I went through the back issues of Four Wheel and checked out the articles (missed about 3 out of the 10) nice articles. I have a similar vintage GMC that I put a 453 Detroit into (probably made about the same power as the 6.2, but sounded way better). If any of you are still a wake, I’m finally done
Patrick
I had over heating problems. Disconnected the radiator cooler. Didn't want to add any heat to the coolant. Added two more air to oil coolers. and still got +200F temps.
Took every thing out and added a 4" x 24" x 1.5" radiator style ATX cooler from a '93 to '95 Taurus SHO. After beating the car on and off at the track in +90F temps the ATX fluid never got over 210F which was at the end of the day.
A properly working TC is important as once locked up there is very little heat produced.
Took every thing out and added a 4" x 24" x 1.5" radiator style ATX cooler from a '93 to '95 Taurus SHO. After beating the car on and off at the track in +90F temps the ATX fluid never got over 210F which was at the end of the day.
A properly working TC is important as once locked up there is very little heat produced.
I'll add this FWIW. I have a Probe GT with the infamous 4EAT trans. I'm using a Long LPD 7.5 X 10 X 3/4 cooler with an 8" dedicated fan. It's plumbed as an auxiliary, i.e., after the radiator cooler.
In this car the engine oil is also cooled by radiator coolant. Before the LPD, the trans and the oil temps were more or less the same, which makes sense. After the cooler was installed, the ATF is generally 30 deg cooler than the oil temp. The oil is generally 210, the ATF 180. In stop and go traffic in summer (Central Florida) the AFT will get up to about 195. The fan will then bring it down about 10 degrees, but a few moments at 30 or so will bring it down to 180 again.
The ATF temp is taken in the coolant line before the radiator cooler. The oil temp is block temp after the filter and cooler. I don't bother with coolant temp, the factory guage is sufficient for me, and is not calibrated.
In this car the engine oil is also cooled by radiator coolant. Before the LPD, the trans and the oil temps were more or less the same, which makes sense. After the cooler was installed, the ATF is generally 30 deg cooler than the oil temp. The oil is generally 210, the ATF 180. In stop and go traffic in summer (Central Florida) the AFT will get up to about 195. The fan will then bring it down about 10 degrees, but a few moments at 30 or so will bring it down to 180 again.
The ATF temp is taken in the coolant line before the radiator cooler. The oil temp is block temp after the filter and cooler. I don't bother with coolant temp, the factory guage is sufficient for me, and is not calibrated.
"The" Jim Allen from "Jeep 4x4 Performance Handbook"?.
Thanks for the numbers from the tests. Good thread to bookmark.
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