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Transmission temps when its nuclear hot

Joel Wilson

Joel Wilson

1/2 ton status
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Jun 7, 2017
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Location
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Today, I had to drive 45 min for a stupid VA appt. I drove 67 to 70 mph, no AC, ambient temp 95 to 100. I turned the transmission cooler fan on once it hit 180.

Transmission temp at the pan was 220 according to the gauge, engine oil temp was 160 on the gauge, coolant at the bottom of the radiator was 150 on the gauge.

Coming back, temps climbed a bit, ambient was a solid 100 maybe 105. Trans was reading 240, engine oil temp was 170, coolant temp was 150.

The 240 was kinda scaring me, so I grabbed the laser gun as soon as I stopped and took as many readings as I could, as best I could.

Engine oil temp at the cooler was 204 in and 145 out. 145 reading was erratic.
Transmission oil at the cooler was 160 at the cooler and at the pan was 180 at the bottom of the pan and 201 at the top.
Coolant temp at the thermostat housing was 190.

This was the hottest day that I had driven the Jimmy on the freeway. Jimmy is a SBC 400, 415hp ish, 3.73 gears, 35's, TH350, NP203 with a mile marker part time kit. Rear end has an Eaton G80. I also had the hubs locked during this trip since I have had problems with the hubs not being locked before and trying to engage 4wd after a week or two of not locking the hubs. I have a 1200 stall on the trans and I do believe I have lost 2nd gear. Transmission pan is +3 qt.

So my question/concerns are the transmission temps. Are they okay, or should I plan on replacing the transmission oil every year, just to prolong the transmission life. I need to check the transmission oil cooler lines to see what they have in close proximity of.

Thanks in advance for any help. 240 scared me a bit.

Joel
norcal
 
infrared temp did not match the gauge temps at every location. I have an external cooler with a fan but it partially obstructed by winch bumper. IR gun is one from harbor Freight but seems to be close when used at other temps at work on various pieces of equip. I am sure that some temps are affected by exhaust. I just need to limit that.

That temp listing is that for 5 min or 30 min? I understand that the higher temps mean bad things in a oil but how long at that temp?
 
Kain said:
might be time to relocate the trans cooler
Click to expand...
I thought about what you said quite a bit over the last week and I got to thinking that we had transmission problems before this engine rebuild and this newer trans so I was trying to think of the common denominator between the 2 and the only thing I can come up with is the exhaust. There is one spot where the passenger side dual comes really close to the transmission lines. I have no idea what the old transmission temp was but the old trans failed and this one is running hotter than normal. So I bought some heat insulation sleeve from Summit (listed on another thread) and am going to insulate the transmission lines to and from the cooler and while I am at it, insulate the fuel lines since they run down that frame rail as well. As soon as it gets here and I get it installed, I will take readings and let everyone know the results. If that doesnt work, then I will put the cooler someplace wide open.
 
I mentioned the Ir and gauge temps, to see how accurate your gauges are.
The gauges that are close to the Ir are probably accurate, and others aren't.
Might have seen all the trans cooling stuff I have done. My next experiment will be to by pass the radiator cooler.
I am happy with temps as sits now, at least with no A/c and not towing.
 
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