Archived Good Trans. gone bad?

[tractorface]

Need some reassurance before my hour drive home this evening.



Finally installed my transmission temperature sender yesterday. I used a new line from desert diesel, It was shipped with the check valve removed at my request. The old check valve came out while removing the old line so I carefully inspected it and made certain I reinstalled it facing the correct direction.



OK, Driving in today (empty) the temp slowly climbed (5 minutes) to 180 and after another couple of miles it went down to 165. I let the truck idle in park for about 2 minutes while I recycled some old oil, got back in the truck and the temp was at 210:--) Continued on down the road and the temp slowly climed to over 250 for the rest of the drive (45 minutes) It did fall slightly at times but not more than a few degrees. Got to work and immediately pulled the dipstick to feel the fluid. It was not warm at allOo. Felt the line that the sender is in and it was cool to the touch as well. This leads me to believe either my sender or the wiring is bad. I am very capable of troubleshooting the electrical portion of this installation and will do so when I get home.



I just want someone to confirm that there is no way the fluid temp could have been over 250 for 45 minutes and the fluid not smell burnt not be discolored and not feel Hot to the touch.

Truck seemed to have driven normally no slipping (I think). A little unsure because I started believing I had a major problem and started to imagine shifting and slipping problems. Probably my deep down desire to replace the 100,000 mile OEM with a full tilt and boogie aftermarket trans.

Thanks for the help.

Now someone tell me its gonna be OK before I gotta add *** transmission to my signature!

 

[keimmmo]

I will be following this post with great interest! I too just installed a trans temp gauge. (Isspro) I run 140 on highway with converter locked. If converter unlocks for any reason, the temperature QUICKLY shoots to 160. I have already hit 195 driving around town. This concerns me since I will be heading from central Mexico up to Illinois with the 35 ft travel trailer in just a few days!!! I am running Dexron III ATF if that makes any difference.



Steve

 

[Greg Boardman-RIP]

I run 180* most of the time in lockup. If you run around in third at a low rpm or backing you will see extreme heat. That doesent mean that you are cooking your transmission. You are reading the fluid right after it leaves the TC. That is the hottest spot.

 

[keimmmo]

What are acceptable temperatures coming out of the trans? I already burnt the ATF once while towing in the mountains... that is why I put on a gauge! I would really hate to have to buy a transmission, but sitting along the road in Mexico with a dead rig could be a MAJOR problem!!!



Steve

 

[Greg Boardman-RIP]

I think 180*-220* are totally acceptable. I would be worried if my transmission was running at 250* for 45 minutes. I would call one of the transmission experts on this site and ask them. Call Fred at Desert Diesel. He will try to help 632-910-9575.

 

[tractorface]

I understand that would be a problem. My question is would the fluid be hot to the touch? Would it smell burnt or be discolored? What would cause this? The only possible scenario i could come up with was some kind of blockage at the check valve, still don't think under no load and a real light throttle foot this is possible.



Thanks for the advice. I will call Fred!



All of the transmission gurus are probably reading the Bind up thread!

 

[parcher]

On a gas passenger car the coolant can be as hot as 220 degrees F. The trans cooler is in the radiator, so in order for the trans cooler to lower the temp of the trans fluid, it has to be HOTTER than the coolant (over 220 deg. )!

 

[tractorface]

Forgot to mention the coolant temp never went above 190. Don't forget also that these trucks use a heat exchanger mounted near the engine as well as the radiator mounted cooler (unlike your gasser). With all that cooling power I was having trouble believing 250+ leaving my transmission. I understand the reading is before the coolers but unless there is no flow I could not imagine temps like this. I may be all wet no real experience to speak of.





Anyway got the multimeter out and discovered the problem. A high resistance ground. The one wire sender uses the line it is installed in as its ground conductor. The line I installed has very heavy paint on it and uses a flexible rubber connection to the cooler on the engine. This leaves the end leaving the transmission as the only path to ground..... of course, not thinking this is also the only place I used any Teflon tape. I did not have time to remove the tape but am certain this will fix the problem. As usual I caused my own problems



Thanks for the help.

 

[B.G. Smith]

ATF

If you want the fluid to cool while the truck is not moving I think you have to put the Trans. in neutral, don't believe the fluid circulates in park. bg

 

[rweis]

Yep, that's true unless it is a xxx which some of the rebuilders mod the VB so it circulates in park. Look in the service manual, in park the fluid circuit is not colored, ie not pressurized.



Bob Weis

 

[tractorface]

Eliminated the ground problem and still get the same readings. The sender is not too hot to touch and the fluid is pink and smells ok..... uugh. Going to pull the sender and test it in some water with a candy thermometer this evening. I am convinced it is not a "real" temperature problem but am starting to wonder. Hoping I will discover the sender is bad this evening. Will also check the gauge with a variable resistor tonight. Not exactly sure of the scale but will do some looking today. Oh yeah crawled under the truck last night and confirmed my membership into the "old 53er's" 53 block... not really worried. There are more importnt things going on in the world.

Life is short, Enjoy it!

 

[tractorface]

autometer z series sender ohms

Just in case anyone is interested below is from an e-mail I received from Autometer. I had asked about normal sender resistances at certain temps so I could properly troubleshoot my system. Quick response also!





100deg/1123ohms 120/708ohms 140/460ohms 150/374ohms 170/253ohms 190/175ohms 210/123ohms 220/105ohms 230/89ohms 250/65ohms 280/42ohms 300/32ohms 320/cooked transmission!

 

[Hohn]

General Comments

If you have a REAL trans fluid temp problem, you will know it from the smell. Petro-based transmission fluids don't handle high heat very well, and will darken quickly. They varnish surfaces under heat.



Redline makes a synthetic High-temp ATF that can handle temps that would turn other ATFs to solid crust. You might want to try that if you find you have a temp problem.



I agree that your sender is probably messed up. ATF @ 250° will not only feel warm, but give you a 3rd degree burn. Keep troubleshooting. Maybe a mechanical gauge would solve this problem, who knows?



One other thing: sometimes ATF can get so hot in our trucks that it will cause the engine to overheat. The ATF gets so hot that the radiator can't handle the extra heat, and the coolant temp will get very high.



An an auto truck, watch your three temps VERY closely, as they all relate: EGT, Coolant, Trans.



Hohn

 

[tractorface]

Thanks Hohn,

(spoken with a Dundalk accent)



I solved the High reading gauge issues and am now seeing very low temps actually. I drive country roads and highways unloaded and have not seen over 165. mostly sits around 135. I think these are probably a little low and will spend a little more time this weekend looking into the system. I appreciate your post, it confirms what I was thinking. Any idea what "normal" temps would be in my situation. I kinda thought the Trans. temp would follow the engine temp a little closer. That is why I am planning to do a little more work. My problem was due to the fact that I made a nice ltlle wire harness back in December and forgot exactly what was what. Got my meter out and solved that, now I just need to check the accuracy of the sender and the gauge.