Transmission Temperatures?

Guardian · January 28, 2003

You guys were such a great help on the last post, I thought I'd try again!

Basically what I'm after is a way to keep an eye on the transmission temperature. I tow a 25' goosesneck trailer over the mountain passes and want to make sure nothing melts. I've heard that someone makes a temp gauge that has a sender that goes between the trans coolant line and the radiator. But I'm not sure who that is. My other question is, is it possible to get another temp sensor for the coolant and splice a 'T' into the HOT side of the trans coolant line, and then use a switch so that the engine temp gauge in the cab could be used to read both the engine and trans temp?

Has anyone done this before? Or am I just crazy?

I'm doing this on a 1991 Chev 3/4 ton, ext cab, 4wd, with the 454 (7.4L) Thanks for all your help on this.

jimb · January 28, 2003

look here.

http://www.bankspower.com/dynafact.cfm

January 28, 2003

Sure, it could be done providing you have everything "matched" and used electrical gauges and senders.

You'd need the same sending unit for the tranny and engine. Split the tranny line, put in the "T" with the sender (Make sure that this gauge is grounded to the engine block!)

Run the wire up to a single pole, double throw switch.

Splice into the wire for the engine temp gauge, making the wire to the sensor on one pole, the wire to the gauge goes in the middle of the switch.

If this is confusing, email me and I'll send you a diagram.

This is actually a pretty good idea. I may do it myself, just never thought of it.

Dan

Guardian · January 30, 2003

Thanks for the encouragement Friz.

I already went out and got most of the parts I think I'll need. Probably need a few more parts runs though, so far I figure I'm into it for about $60. I'll keep you posted as to if this works or not. Should have it done in about a week.

Thanks Rob

titanium10k · January 30, 2003

hey guardian I was thinking of adding the tranny temp gauge also...where are you gonna mount yours and what brand are u gonna get.....

Guardian · January 31, 2003

Actually I decide to go with using the original engine temp gauge (mine has actual numbers). Installing a toggle in the dash so I could flip it up to read the engine temp and down to read the tranny temp. It's basically the same concept as the fuel gauge when you have two tanks that read off the same gauge.

After talking to numerous transmission rebuilders and aftermarket people they all agreed that the best place to put the sending unit was in the transmission cooler line (the hot side coming from tranny to radiator) if you put it in the pan or the return line to the tranny it gives you a false low temp.

If your going to use the existing gauge in the dash, go to the dealer and get the exact sending unit the gauge already uses. They're about $22.00 Westach also makes some nice gauges for your tranny.

Your tranny should run ideally at 200, but when towing or pulling heavy loads it will usually run a bit hotter. You might also want to check out MRTRUCK.NET he has some sites listed that sell aluminum pans that hold a couple of extra quarts. Beware the chrom ones though, they have a tendency to hold heat in.

Rob

awdvkd · January 31, 2003

Why can't you just use the line pressure test port on the side of the transmission instead of using a "T" in line. Wouldn't you get the actual temp inside the tranny. Its the correct tap size and easily installed. (700r4) ???

Guardian · January 31, 2003

If you got the test port, then use it! I just don't happent to be that lucky my truck has the 480LE tranny (the early model) and as far as I know it doesn't have a test port. (Someone correct me if I'm wrong) That test port sounds like an easy way out. Soon as it quits raining I think I'll climb under and take another look.

Thanks for the info.

Rob

titanium10k · February 1, 2003

does the 4L60E have this port??????????

mnstrmdnss · February 1, 2003

it just so happens ive been looking into this idea, also. ive got a wonderful technical source at my shop called Mitchell. i have complete wiring scematices for my vehice, and i can get them for any vehicle(hint,hint!). the easy part i can say is that in my 98 4l60E, their is a transmission fluid temp sensor already in the tranny, which is the same resistance values as the coolant temp sensor. im 99% positive that all 4l60E and 4L80E trannys have them.

now the down side, the instrument panel. the only way to properly feed the gauge would be to actually hook the middle of the dpdt switch to the temp gauge---not easy considering its all a printed circuit board. you could take an easy way out and connect the dpdt switch between the two temp sensors leading to the pcm, which WILL work, cause the pcm directly controls the temp gauge, BUT the computer will also see a difference in temp and if the tranny is nice and hot, the computer wont know the difference , it'll just adjust fuel trim settings to compensate for higher temps.

this is true for the most part on 94' up, not quiet sure on a 91. but like i said, let me know and i can get you your vehicle wiring scematic.

Guardian · February 1, 2003

Well I guess that makes sense that the tranny would have a temp sensor, otherwise how could that pesky check engine light come one? Do you know if there is a way to tap into that sensors wires?

Would the wiring schematics be the same as in the Hayes Manual?

I did learn that the port on the side of the tranny can be tapped into for a sensor, but it is cautioned against for two reasons. First being that it is for pressure testing, and second that it may not give an accurate hot reading (May read cooler than it actually is.

Thanks for all the contributions,

Rob

P.s. I'm sure there is a very complicated way to do this simply.

mnstrmdnss · February 2, 2003

my email is [email protected], email me with your email, and i can send you a scematic of a 4l80E, which i presumably believ you have.

February 2, 2003

P.s. I'm sure there is a very complicated way to do this simply.

If it don't hurt, we aint doin' it right

americanmuscleman · February 9, 2003

There is a tranny temp test port in a 4L60E. You can screw a temp senser into the side of it. I installed a tranny temp gauge on my camaro (same basic 4L60E), and put a "T" in the output line of the tranny. Only after I did that did I realize there is a test port in the tranny that a temp sensor will screw into. Your tranny temp gauge will read perfectly fine being in the output line though. The factory temp gauge in my camaro's 4L60E reads exactly the same as the one I have installed in the output line of my transmission (I verified this will reading my engines computer with a laptop, and comparing it to the temp my aftermarket gauge indicated).

I really like the AutoMeter electric tranny temp gauges. They include the temp sensor, multiple fittings, and the gauge I have is dead-nuts accurate.