I'm sorry, I just have to rant here. I am getting so tired of hearing everything under the sun when it comes to transmissions. I got my dad a temp guage for his truck since mine seems to run consistantly 240 or hotter.

Sending unit placement. Some say the line going to the cooler is best and T it in there. Some say a bung in the pan is the best place for it. Some say that the test ports on the side of the transmission are best. So who is right?

Now for the temps. Everywhere I have looked state that 175* is a really good temp for ATF. I've talked to two different shops here in town. Shops that I would assume know their stuff since they work on these things every day. They both told me that 200* to 240* is perfectly normal for the 4L80 in a one ton dually. WHAT?????

So no one really knows where to put a temperature sending unit for a transmission and no one really knows what temp a transmission should run? Interesting.

I do not like seeing 240*+ on my guage. I will cure my problem one way or another.

I just bought another transmission cooler. I do not like the one that is on there. I think it is restrictive both air flow and coolant flow. This is a Tru-Cool # LPD4739 cooler. It is a plate fin design. It is pretty large at 1.25 X 8.5 X 22.75, but it seems so tight and constrictive and the plates just don't seem like they would flow real well.

So now I bought a Permacool tube and fin design. This unit looks like a beast. It comes in at 1.5 X 10.5 X 21. It has a large tube that coiles through the fins. The fins are spaced quite well with lots of air space in between. To me, this seems like a better design. I will install it in my truck hopefully next week and I am hoping that this cures it. If not, I'll put both of the damn things on the truck! My goal is to see 180 pretty consistantly with the understandable spikes when I am towing my 32 foot gooseneck loaded with a 10,000 + tractor on it.

Sorry about the long rant. I'm done................................for now! :lol:

Just a heads up. On my 4L80, the temp at the test port and the temp on the transmission line going to the cooler are WAY different temps.

When it was in the test port, I was consistantly seeing 200 + temps. I moved it to the line going to the cooler and I have not seen 200 yet and I went to lunch through stop and go traffic. The highest I saw was 190 and that was when I was working at getting into a spot here at work.

Not sure if this is good or bad, but the temps are definitely different.

FWIW, a 4L80E does have a tranmission temp. sensor built into the hydraulic switch on the bottom of the valve body. The switch tells the PCM if the transmission is overheating. The PCM will then delay shifting, boost line pressure, and keep the convertor locked as much as possible. You can read the trans. temp. with a good scan tool (Snap-On Modis, G.M. Tech-2) while you are driving. Many of the later trucks have a trans temp. gauge, and I think it uses this same sensor. Now, if you mount an aftermarket temp. gauge in the line going from the trans. to the cooler, you are going to see a high temperature because that fluid is coming straight from the convertor, where the fluid is the hottest. The line coming back from the cooler to the trans. is probably going to read too cold, and not really be accurate either. I think it is best to read the fluid temperature in the pan.

That's where I would like it. I want to move it some day. I need to drop the pan soon to change out the filter since the rebuild. The truck sits very high and being a dually, I don't plan on off roading with it so I would like to get a deep pan with temp bung in it. But they don't give them away! For one that is aluminum, finned, sending unit welded in, deep, and an extension for the filter is over 300 bucks.

Best place for a temp gauge is in the pan, then you know the temp of the fluid before its sucked up and sent threw the tranny. 175* is considerd perfect, not what it HAS to run. 200* on a stock vehicle with no aftermarket cooler is the norm in my exsperience. FYI- I had a built 2004R in my 79 c10 with a vortec 350, 3.07 gears and a 2300rpm stall convertor. I ran the biggest cooler b&m makes after the stock radiator cooler, and my temps wouldn't go over 180* on a 110* day in stop and go driving. In the winter it wouldn't even hit 100*, and I think thats a bit too low.