trans temp sender

[JIM S.]

I just installed a trans temp gauge from TST and the instrutions say to put the sender in the forward test port on the pass. side of the transmission..... but it seems like I saw a post talking about how that was not a good idea! like the sender could stick out too far and a (thing) could hit and cause big trouble! am I thinking of the right thing? or what... I am not wanting to drive the thing till I know... anyone. and were is the ideal place for mounting the sender if the place I have it is not good? ... . Jim

 

[DieselB59]

You can put it in the first port. If you're really worried about it, then use the pressure test port, the second one back. It'll only work in drive, but really what else would you need it to read in? I put the Ford ones in the pressure test port because you need to weld to the pan or buy a new one, and some people want to do neither. You can also buy a Mag-Hytec pan and just put the sender in the hole that the pan has for it.

 

[illflem]

I use the second test port (middle one on pass. side) on my '95 because it already has the stock sender in the output line port. Easy to do, works just fine and costs you nothing. Avoid the pan, it will give you low enough readings that your AT may already be over-heating by the time it registers.

 

[ProvenPerformance]

Illflem-



How similar are the readings seen when fluid temp is sampled in the test port and the trans line? Is the test port going to give me much cooler temps than what the line temps would?



Thanks!

 

[illflem]

PP, the readings are supposed to be very similar, but as Chris said only in drive. Just be careful in Reverse when backing up a trailer, I've heard reports that the only time some folks have gotten high AT readings is while trying to jockey a travel trailer into a tight campsite, there is less airflow though the cooler in reverse. Bill K recommend the middle port to me since '94 & '95s use the output line tap for the stock sender. Another alternative on 94-95s is to remove the stock sender and replace it with a resistor, I'm not sure of the value. Yet another way is to add a compression tee to the output line for the sender, I personally wouldn't go this route for fear of a potential leak.

 

[ProvenPerformance]

Thanks for your help... . I APPRECIATE IT!

 

[Extreme1]

I've done it in 3 places...

The forward test port, the pan and the line out.



The pan and the test port will give you the same very low readings. My guage (Isspro) reads from 140 to 320. The pan and port read about the same but the hottest it ever got was about 160-170 on a hot summer day in traffic pulling a trailer.



With the sender in the line, the temp measured is much higher and fluctuates much more. Sitting at idle at a light will raise the temp to 200+ on a hot day in no time. Pulling a load up a grade (on ramps around here) is worse. You should see how fast it drops when the TC locks up. Then it will read 170ish if on a warm day.



Reality Check: On a recent trip to California, pulling a small but heavy trailer on the Needles highway in SD, I had the trans temp guage pegged. (Kick down cable not set right. ) Yes, the warning light does work. It turns off at 265 and on around the same temp. (Glad I updated the lines before we left!)



For the ultimate, put a sender in each location and switch between the two.



If you already have the line with the temp port (94-95), update that line to the one with the short section of hose at the block mounted cooler end. (Latest revision. ) Take the factory hose off (it has a check valve) and throw it or put it in your boonie box for a spare. Make up a similar section of line but use a 1/2" pipe T, a 1/2" hose barb to 1/2" pipe, a 1/2" hose barb to 1/2" (-8) inverted flare (same as an AN fitting for this size only), a 1/2" nipple (short) and about 6" of transmission hose. You will also need a bushing for the temp sender. I got it all with one trip to the local hydraulic line shop.



Install the T with the nipple in the block mounted cooler before the installing the sender as there isn't room to turn the T with the sender already in it.



You will end up with a hose section as long as the factory hose because theirs has the check valve.

 

[GOakes]

According to my '97' Service Manual, Dodge measures this temperature in the pan. Then, some will tell you -- "they don't know what they are doing". Or could it be-- that those Dodge engineers just might know things about their trucks that they aren't willing to share.



Simply stated:

(1) The oil in the pan will be pumped into the working parts of the transmission to lubricate and cool those parts.

(2) If that oil gets too hot bad things start to happen (and rite now) !!!!

(3) The torque converter is by deign a heat generator. A whole engineering paper could be written on that subject and that would be little more than a primer.

(4) Using the TC discharge oil temperature as a data input to any meaningful measurement would require more than a casual knowledge of automatic transmissions.

I measure my transmission oil temperature in the pan. It is (in my opinion) the first and best indicator of oil cooler failure.



As to the over heating while operating in reverse --- how about stop and go traffic ?--- maybe that's the reason for the water to transmission oil cooler.

 

[illflem]

GOakes, you are correct about Dodge measuring the AT temp in the pan from '96 on. '94&'95 are measured in the output line to the cooler. You've got to wonder why they changed, was it because it's better or because it saved them a buck. I have a feeling it was the later.

 

[EMDDIESEL]

Transmission cooler failure is a non issue, it has no moving parts, it either works, or it does'nt, IE blocked or leaking, in which case you will know right away when you trannie ceases to function or you temp sensor mouted elsewhere cause you gauge to rise rapidly. So mounting a temp sender in the pan only for that reason is a waste of time. The reason for mounting the sender in the output from the trannie to the cooler is this way you know what you trannie is doing, if your trannie is heating up fast, you will know right away. A pan mounted temp sender will show you the temp after the fluid has been cooled and then allowed to cool further with the fluid in the pan. Think of driving in 0 degree weather and how fast your trannie will cool and if you are getting a reading from the pan it will be MUCH cooler then a reading from the output line. Therefore you will not see a problem anywhere near as fast as if you were taking the reading right after the fuid is used. Something to think about. Just because its easy to mount a sender in the pan, does not mean its a good idea. Dont forget, no pain, no gain.

 

[Extreme1]

GOakes, It is measured internally but I don't think in the pan. I am not sure about the newer vehicles but the '94-95 models won't upshift when "cold" (below 45 as I recall).



I have to drive about 1 mile when it is in the mid to upper 30s and 1 1/2 miles when it is around 0 before it upshifts. The sensor is in the stock (cooler line) location and this is typical. If the sensor were in the pan, it would take much longer to upshift.



When my first transmission failed (too much heat) the warning light never came on. How hot was the pan temp? No idea, no gauge. But the overheated section was in the overdrive unit. We were driving in 15 degree temps at high (80 mph) speed and towing boxy but not too heavy trailers. I am pretty sure that the cooled fluid would have supressed any indication that doom was impending. Especially since the failure was caused by lack of lubrication and, consequently, wouln't have had a significant volume of hot fluid coming into the pan to offset the "normal" pan temp which is way below 140 in those conditions.



But, like I stated above, for the ultimate, put a sender in each location and switch bewteen the two. I plan on doing this when I decide where to locate my switch panel.