Those look to be the best places to start!

 

And the results are in.....

Been working on this for a while and now have some good data on what my truck runs for rear diff and transmission temps.

I used surface mounted RTDs and put one on the rear diff cover and one on the transmission oil pan. The rear diff still has the original steel stamped cover however I have changed the oil several times and am now using 75-140W synthetic oil. The temperatures are with and without my 5000# trailer in tow.

The rear diff temps ran between 120-150 degrees depending on speed and outside temps when I wasn't towing. With my trailer in tow the rear diff temps ran between 180-200 degrees at highway speeds in 90+ degree weather. The highest I saw it hit was 210 degrees after a good steep grade on the interstate.

The transmission oil pan temps ran around 150-160 degrees all of the time even when towing. I will put an RTD on the oil line going to the cooler before my next trip to see what the temperature difference is between the oil going to the cooler and the oil in the pan.

For a reference point the transmission temp gage needle was sitting just below the middle of the gage when the temps were in the 150-160 degree range.

 

You must have been reading my mind

I recently bought a PC fan control/temp monitor unit. It comes with 4 temp probes, which I intend to extend the wires on and mount on the Rear Dif, trans line, oil pan, and outside air temp.

The unit itself has nice silver face without excessive markings for PC type data. It also has a one line large LCD display that does not label the temps as 'Hard Drive' and 'CPU'. It also has temp alarm set points for each sensing circut.

The only fault I have found so far is the max temp reading is listed at 180 degrees F. I think I might be able to modify that a bit.

It will be August till I can play with this, which is a shame. Next week we leave on a 6,000 mile cross country trip. It would be nice to watch these temps up and down the Rockies.

 

You must have been reading my mind

I recently bought a PC fan control/temp monitor unit. It comes with 4 temp probes, which I intend to extend the wires on and mount on the Rear Dif, trans line, oil pan, and outside air temp.

The unit itself has nice silver face without excessive markings for PC type data. It also has a one line large LCD display that does not label the temps as 'Hard Drive' and 'CPU'. It also has temp alarm set points for each sensing circut.

The only fault I have found so far is the max temp reading is listed at 180 degrees F. I think I might be able to modify that a bit.

It will be August till I can play with this, which is a shame. Next week we leave on a 6,000 mile cross country trip. It would be nice to watch these temps up and down the Rockies.

Are you going to be towing anything on your trip? If not 180 degrees will probably be all you will need.

If you are interested I have a few extra RTDs that I would gladly send you. I got a whole batch of them on eBay for $5 so just PM me with your address and I can priority mail them on Tuesday to you no charge. All I ask is that you post the info when you get it.

You just need an ohm meter to read the resistance and I have a conversion chart to get the temperature.

 

Are you going to be towing anything on your trip? If not 180 degrees will probably be all you will need.

If you are interested I have a few extra RTDs that I would gladly send you. I got a whole batch of them on eBay for $5 so just PM me with your address and I can priority mail them on Tuesday to you no charge. All I ask is that you post the info when you get it.

You just need an ohm meter to read the resistance and I have a conversion chart to get the temperature.

That's a nice offer!

I think I'm ok with what I have. I also have a few infrared pyrometers as well as probe pyrometers around.

I'm looking at converting this PC unit because it has such a nice looking face plate and meets all my other requirements, (mostly). It will be mounted in the dash above the center tray, and should blend in nicely there as a permanant fixture.

I miss not having ambient air temp, so as long as I'm going after that I'll also capture data on the rear diff, trans, and oil as well. It has four channels to use......

I like the idea of having alarms as well. Be nice to have it BING when ambient gets to 33f or the trans gets hot.

For the upcoming trip I will toss one of my infrareds in the glove box and just aim it at the Dif and trans occasionally when I stop for fuel. That should give me a fair idea of what temps they run at. I won;t be towing anything so I'm not looking for anything unusual to occur.

 

Updated info on transmission temps

Update 7/27/05. Some new data points:

Another trip with my trailer in tow, outside temps in mid 90's again. A 250 mile trip up to northern New Hampshire on I93 at speeds around 60MPH. This time I had the line going out of the transmission to the cooler instrumented as well. The rear end temperatures stayed in the 180-200 degree range and the transmission oil pan temps stayed in the 150-160 degree range. The outlet line from the transmission to the oil cooler ran about 170-180 degrees (about 15-20 degrees above the pan temperature) normally but anytime the transmission came out of lock up the temps would shoot right up quickly.

I ran it in D and in 4th to see what the temps did. In 5th the transmission tended to hunt and come out of lockup quite a bit which caused the temps to go up. In 4th the transmission stayed locked up more so the temps stayed lower overall. However even in 4th on steeper grades when the transmission started to shift around it would come out of lockup and the temps would go right up.

I found that at lower speeds the tranny tended to come out of lockup quite a bit and the temps were actually higher than at highway speeds where the tranny stayed locked up more.

The highest temp I saw on the cooler line was about 210-220 degrees before I shifted it down to cool it off. The pan temp never changed noticeably during any of these temperature transients as they were all short term. What this means is that the temps coming out of the tranny can run quite high before you see it on the temperature gauge.

Bottom line is if the tranny is not locked up and you are towing, the tranny temperature is going to go up quickly to over 200+ degrees and stay there for a while before it shows up on the gauge.

On the way home next weekend I'll try to see exactly how high the outlet line temps need to go to cause the gauge reading to go up.

 

Interesting stuff. I have a carputer I will be installing soon (I hope) in connection with the avelectronic video switcher for the OEM NAV screen. The carputer could run temp logging & alarm software in the background and produce an audible alarm if I can find the right probes & software.

 

Locks up in 4th?

Does this trans give a solid lockup in 4th and other lower gears.I thought these "lockup" transmissions only gave a solid-metal to metal(or fiber plate) lockup like a manual transmission lockup in 5th gear?Clear this up for me?Thanks.Charlie

 

Re: Locks up in 4th?

Does this trans give a solid lockup in 4th and other lower gears.I thought these "lockup" transmissions only gave a solid-metal to metal(or fiber plate) lockup like a manual transmission lockup in 5th gear?Clear this up for me?Thanks.Charlie

Yes, The converter will lock in 4th when that gear is manual selected and the scheduled speed, rpm and throttle position is met.