Quick answer is "it depends"...

If are cruising down the road and the TC is locked up, you'll probably find that both temps are the same.

If you are running in town and not getting the TC locked all the time (or running in reverse up an incline), you will probably find the output line temp will rise quicker then the test port temp.

This is because the output line will be showing you the temp of the fluid after it's been heated up by the unlocked TC. It'll go thru the coolers and back to the pan where it'll be cooled down some, so the test port temp will not necessarily show this 'spike' in temp.

Conversely, once you lock the TC, you should notice the temp go back down pretty fast too.

Either location is fine. You just have to know how to interpret the results based on it's location IMO.

I like the output line temps myself. Others will favor the test port, or even the pan directly.

Mitch

 

Thanks Mitch, yeah I am planning on using the output line, I want to see the hottest that fluid gets.. I had one in the pan and I just didn't like it, it was so slow to change that I could have burnt the transmission up before I saw the rise in the pan..

 

i have mine in the test port and thats where the ford trans engineer says to put it.

 

The output line will will be anywhere from a similar temperature to 100°F or more hotter.

The temperature in the output line varies a lot depending on whether the torque converter is locked or unlocked. I''m interested in the temperature of the transmission, and you can get that from the test port. The output line temperature is going to scare most people for no reason. It will not be that unusual to see 300°F in the output line, and that doesn't mean something is wrong.

 

Ok so what about information like this- http://www.txchange.com/heatchrt.htm Don't temps that high seriously break down the fluid?? I am not a tranny engineer by any means, but if the fluid coming out of the tranny is hot, doesn't that mean the transmission itself is that hot?

 

Plan on using Amsoil fluid.

 

I actually made my order for amsoil last night!

 

[QUOTE=SupercrewLightn; Don't temps that high seriously break down the fluid?? I am not a tranny engineer by any means, but if the fluid coming out of the tranny is hot, doesn't that mean the transmission itself is that hot?[/QUOTE]

It then goes through the cooler, those temps are closer to what you'll see in the trans. Unlocked converters make a lot of heat, esp. for extended periods like a long pull uphill.

 

I've only seen a high temp of 210* out of the output line? That was pulling a 5% grade in 90*+ weather, towing a #5000 TT in 2nd gear with the A/C on. Engine temp was at 210* also.

Found that the TC was still unlocked in 2nd... I matted the gas pedal and that triggered the TC to lock. While still going up the grade, the trans temp dropped to around 195* for the rest of the grade.

Once over the top, the engine temp dropped to 195* and the trans temp dropped to around 190* I'd say.. (over the 180* mark, but not to the 195* mark..).

Been running the Water and Trans temp gauges for over 7 years now and it's been consistent in it's temp readings the whole time.

I've got the old E4OD that calls for the standard 'MERCON' fluid and I pick up the gallon jugs from Wally Mart with that spec on them. Do a pan drop every other year and a pan drains in-between the drops from the drain plug I added to the pan. About 6 qts each time. Nothing significant comes off of the magnet at all either. No residue in the pan either. Just nice pink fluid...

Almost 228,000 miles on it so far!

I've seen 210* on the 1 mile drive from the freeway to my house towing the TT. I'm learning how to keep the TC locked more on that 1 mile trip and can keep it at 180* now..

Just my experience with it...

Mitch

 

Output out of the trans. or out of the cooler?

Good info!

 

out of the trans.. I tapped into the line up front going to the upper part of the rad.

Mitch

 

According to that chart, yes, those temps destroy your fluid and will ruin your trans very quickly. The part that they leave out of that chart is that they are flat out lying.

Not modern transmission fluids. 300°F is nothing to them.

The output temperature of the transmission is how hot the torque converter is getting, but not the transmission. The transmission will be A LOT cooler. That's why there are transmission coolers, to bring this temperature back down to where the trans needs to operate.