See sigline for truck info. I just took a trip from MT to CA. My tranny gauge would occasionally suddenly go up to the 180/190 deg range - usually, it reads about 65 deg above outside air temp. It would stay there for a while and then all at once drop back to about 150-160 or about 75 deg above outside temp. Fluid level looks normal. I don't think it is a gauge malfunction as the vast majority of the time it read correctly. It looked like a blockage that suddenly broke free. Had I not had a gauge, I would have had no idea anything was potentially wrong.

Any ideas?

Has anyone had a tranny gauge in their truck when the tranny failed? What is the most common part that fails in these trannies? Wondering if I should replace something before total failure occurs.

 

Were you towing anything or empty? Maybe a filter change is in order. Hopefully Mark the tranny guru will see this thread and chime in.

When I had a tranny go south on my previous PSD, the gauge shot up to about 220 while towing some gradual hills with my 5'ver and I noticed it was loosing power. I pulled over when I found a spot and it lost all forward gears and they didn't come back. Had to be towed off a mountain.

 

I was empty when it started on the outbound leg of the trip and had maybe 1000lbs in the back on the return leg and it didn't seem to change anything. What I find interesting is the sudden, abrupt temp changes of 30-40 deg. It didn't seem to matter if on flat ground or up/down a hill.

 

You could have a sticking trans cooler bypass valve.

There's a detailed description on this LINK And how to test it.

 

well mine will go up to 180 around town i take it thats a bad sign....but "cruisin" at 60 on the hwy i run about 150

 

Another question, where is your temp sender located? On the line, test port on the driver's side or pan???

On edit: I guess that was two questions...

 

No, that's not a bad sign, that's absolutely normal. Nothing wrong at all.

 

When the temp went up were you cruising on the freeway, or were you in slow speed traffic, or in stop and go in the city?

Even if there were a blockage (and I doubt that there is one) the temp can't come down very quickly when it clears. There is a lot of mass in a trans and it takes several minutes for the temp to drop 30-40 degrees.

I see three possibilities:
First, you went from steady state cruising with the torque converter locked to a different condition where the converter isn't locked. An unlocked torque converter makes more heat than a locked one, so the temp goes up.

Second, something could be a bit flakey with your gauge.

Edit: Third, you might have the sender in the line to the cooler. When the torque converter unlocks the temp in this line will jump up in a couple seconds. When the torque converter locks the temp will drop in a couple seconds. This is normal, there's nothing wrong with that.

 

My BTS is 55 above ambient with the 6.0 cooler. Still, IIRC, my stock unit was about 75 above. At 180, doesn't that mean ambient is 105?

 

That's what I was thinking, Mark. My old Bronco was plumbed in-line and it behaved just like that at times.

 

Anywhere from 60 to 100F above ambient is normal. In stop and go traffic, towing, or with the sender in the cooler line you will see more than 100F above ambient.

There's nothing at all wrong with 180F. The trans is designed to run it's whole life around 180F.

 

I am at 55 above ambient. Is that too cool?

 

Thanks for the reply.

1) I was driving with cruise control set at 2000 rpm on flat ground (I -80 in Nevada).

2) The sender is near the bottom of the tranny in the port on the side.

I was not constantly watching the temp gauge. It would be running normal around 150 and then suddenly I would see it at 190. I did see it drop from 190 to 150 in about a second a couple times. It would hold 180-190 for a random period of time varying from 5 minutes to close to an hour. Then it would abruptly drop back to normal range. In 2000 miles of driving, it did it maybe a dozen times.

 

Test port on drivers side.

 

[quote=MTMike;6427416]Thanks for the reply.

I did see it drop from 190 to 150 in about a second a couple times.

Physically impossible. To much mass. Gots to be a sender problem. Check/clean connections, look for a pinched wire. Swap the sender.