4L80E Where do you take temp readnig (aftermarket sending unit)
 

I have mine in the port behind the range sensor. On a long highway drive it's getting up around 200-210. This is the basically the same as engine temp which makes sense to me since they are bolted together but I am seeing guys on there running sub 175 degree trans temps. Where are you taking your temp readings for that? I don't really want to modify anything to put the sending unit somewhere else. I do have the biggest B&M cooler and the radiator cooler is bypassed. The temp ran about the same before and after the B&M (maybe 10 degrees less with bm). Yes the fluid is pumping and has less than 1k miles on the swap.

I'm not sure on the 80, but I used the pressure test port on the 60 and had a problem with the sending unit...
After seeing this on Ls1tech, I was concerned:
Attachment 113220


some over there have used a shorter sending unit
#2259
Attachment 113221

Just to check, I measured the depth of the port with an allen wrench. it was close...
so I colored the end of my sending unit with magic marker and slowly snugged it up.
it wore the magic marker off the sending unit, so I picked up the shorter one.

Attachment 113222

I have a mine running from the transmission to the stock, in-radiator cooler, then to a 40k tru-cool. I'm running ~130* - 140* in the summer. I've seen it get as high as 150 in stop and go traffic with my 3k stall.

During the winter, it rarely gets above 120*

Your temps seem a bit high, but again, I'm not used to a 4l80. You can T into your supply line from the transmission with an autometer block (or something similar) if you don't want to tap into your pan.
http://www.autometer.com/img/products/2287_d.jpg

Otherwise, you're pretty limited.

Some people install a bung on the pan but that 11mm port by the PRNDL switch is fine. If you havent already, id suggest grabbing a Truc-cool 40k trans cooler.

yeah, 10* is not that much with the B&M. Mine dropped 40* with the tru-cool.

I don't have an 80e yet, but I just drilled and tapped the side of my Hughes cast trans pan on my 60e, and with a tru-cool 40k I rarely get over 160deg. on my autometer fullsweep, even daily driving in traffic in summer with lifted 4x4 and loose 3600 converter.

IMO it needs to be in the oil pan or the return cooler line. I have never seen a factory transmission from any manufacture put it in a pressure port. The trans from the factory has a sensor located inside the oil pan. That should tell you something.

From looking at the B&M site their biggest (transmission) cooler is a measly 14,400BTU. That's a piss-ant cooler and is totally inadequate for a truck application where it's run in a dedicated cooling configuration. Now if you have their Universal cooler that's 1.5" deep it gets to 29,000BTU but the design will restrict airflow unless you have a fan mounted to it.

FYI, your in-tank radiator cooler can dissipate 18,000BTU so you're not actually doing anything with the B&M transmission cooler.

Get a Tru-Cool MAX and you will see the temps we talk about here. It is rated to dissipate 45,000BTU and is leaps and bounds better than the B&M coolers in terms of airflow resistance and cooling capacity. My 80E runs at 140*F on my Tru-Cool.

Why are you measuring transmission temperature? Is it to monitor how your transmission is doing or how well your cooler works?

Pan, Port or discharge.

each is going to register a bit different temperature.

IMO mounting the sending unit in the return line is useless.

Its to make sure you dont overtemp it, you want to monitor the temperature of the oil that is being supplied to the trans.

i was asking a rhetorical question.

but you just mentioned 2 different things:

1) you don't want to overheat the trans.
2) Monitor the temp of the oil that you're sending to it.

What I'm saying is if you're wanting to keep check on the transmission temperature (or oil temp) in order to keep it from overheating, you want to watch the temperature where it get's the hottest.

If you have your sending unit in the return side (the line going TO the transmission FROM the cooler), you're reading the temperature after it has already been cooled and you won't see the damaging spikes until it's too late.