Inaccuracy of trans temp sender in pan


Active Member
May 24, 2001
I just installed a trans temp guage sending unit in the pan. Also the aux trans cooler is plumbed after the radiator trans cooler. Temp guage shows 240 deg normal driving. Is it that inaccurate mounted in the pan (40 deg)? Checked fluid and it is a little over full. I think Bruce recommends it be plumbed at the trans return line fitting, but this was just as easy since i had the trans out anyway.
Unless gauge is wrong

You got problems. Should never see 240 driving. Pan is actually cooler than the return line. If it is truely 240 something is wrong. Ck it with an infrared gun. That will tell you.

Where is there a place on the side of the tranny that I can put my tranny temp sending unit into?
I was told there is a place that is already threaded for 1/8 pipe thread that would give accurate temp readings??? I believe it might be on the DS of the tranny and used for line pressure testing, is this correct? TIA
Yes the port for mainline is.

But that will not tell you either. You want to put in return cooler line at trans. Bottom. Just go buy a 1/4 pipe tee with female, female, male threaded tee. Then put a 1/8 pipe to 1/4 pipe bushing in. Put your original fitting back in tee and go. All you are doing is adding a section. If you would like I think they are 18.00 from us and can be purchased at any good auto parts store and/or your local hydraulic fittings place :)
AND... Totally removable , at any time without altering.

good luck.:D

Out of curiosity, why would we want it on the return line after the cooler??? Wouldn't we want to know the temp of the fluid before it's cooled to give us a more accurate number of what the tranny is doing as far as building heat is concerned??? Also, which is the return line, the upper or lower port, this is where you mean.....right, on the P/S of the tranny towards the front? TIA
BTW, I'll take two of those fittings, you have my card number and shipping address.
Yes.. the reason is...

Actually the t/c is a heat pump. That will be the true temp of the heat that is being generated. Cooler lube is discharged directly out of converter. Trans needs lube more than cooling as there is very little heat produced other than the clutch or band friction. Hell for years they didnt even have a cooler. The t/c is your heat source and pan temp can be stagnent oil. Mainline port capped off is at the end of a pressure circuit so fluid there is trapped also. If you flowed it to a source it would tell you what pump temp was but not what true temp or heat generating temp is. I know this can be confusing but ask any trans guy and maybe they can explain better with an example at hand. And yes bottom port is return line back to trans. That is where you would like to put temp fitting. I will have Mark on it tommorrow. :)

Well, it looks like the Autometer guage or the sender is bad. Now the trans temp guage goes to max (250 deg) and beyond in 2 minutes of normal driving. I drove the car 10 miles normal driving and then checked the temp of the dipstick and fluid on the stick. With the guage still pegged, the fluid is barely warm and the dipstick is same. Car shifts normal, and does not smell hot and fluid does not smell hot. Anybody else have this problem with Autometer temp guages?
Nope, not usually, they are very good

Thats all we sell and install. The one thing I have run across is in 1999 I think they changed the sender and the reading at the gauge. If you mix match early and late it has a tendency to do this. Also if sender wire is touching ground ANYWHERE it will do exactly what you are describing. Ck again for all wires to be touching nothing and/or cut somewhere. Look at the attaching stud and nut, on sender, as we once had one that didnt have the little plastic washer that isolates and it did that too.
Let me know.