700R4 temp monitoring

[MrJames]

Brokenwrench

I am just curious as to why you believe that monitoring the fluid temperature from the cooler(s) back to the transmission is the best location. It seems to me that this location will inform you as to how well the cooler(s) are functioning. The transmission could be sending out 300 degree fluid and you wouldn't know it in this location.

I wonder if having two sensors, on a switch to the gauge, on both the output and input lines would be more informative.

[1Gary]

Brokenwrench

I am just curious as to why you believe that monitoring the fluid temperature from the cooler(s) back to the transmission is the best location. It seems to me that this location will inform you as to how well the cooler(s) are functioning. The transmission could be sending out 300 degree fluid and you wouldn't know it in this location.

I wonder if having two sensors, on a switch to the gauge, on both the output and input lines would be more informative.

Having a switch sure would cover it and I think is a great idea. =D>

[brokenwrench]

Brokenwrench

I am just curious as to why you believe that monitoring the fluid temperature from the cooler(s) back to the transmission is the best location. It seems to me that this location will inform you as to how well the cooler(s) are functioning. The transmission could be sending out 300 degree fluid and you wouldn't know it in this location.

I wonder if having two sensors, on a switch to the gauge, on both the output and input lines would be more informative.

There is little that you can do to control the heat that your transmission produces, all that you can do is cool it within desired parameters and pump cool fluid back to the transmission. If you look at the fluid flow schematic for the transmission, they send the predictably hottest fluid out and return the cooled fluid to the supply for the entire system. Ideally the mixing that occurs in the transmission keeps the fluid at the ideal of 175 degrees, which is ideal for seal performance. Heat, within reasonable limits, does little damage to metal and clutches. It is damaged seals that cause fluid pressure decrease, slipping clutch packs, and then clutch burnout. Electrical component failure has added a new dimension of psychosis but fortunately it is reasonably reliably monitored by the computer and warning light system. If you want to monitor fluid heat going out, then you need to decide if you are going to pull over at the side of the road when it reaches which temperature????????????

[MrJames]

I assume that at 230 degrees I would stop towing a load to let it cool down or change my driving it hard antics. At this temperature it may have already burnt the fluid. I would at least know what was happening to attempt a cure before it got worse.

[brokenwrench]

I assume that at 230 degrees I would stop towing a load to let it cool down or change my driving it hard antics. At this temperature it may have already burnt the fluid. I would at least know what was happening to attempt a cure before it got worse.

If you are getting 230 degrees returning to the transmission, yah, shut it down. Fluid gets burnt from clutches slipping causing extreme heat. There is no problem with a lot of gauges other than risk of leaks with the more plumbing that you have. Van will start to look like a 747, which might be cool. I am thinking of fabricating a dash mount gauge cluster from fiberglass for my own gauge obsessions. How many holes would you want in yours?

[1Gary]

On Ole Yellar because it will be a high top conversion,the plan is to locate the gauges where the stock radio goes and relocate the radio to the overhead.I will plasma cut diamond plate the size of the plastic I have cut out to mount three gauges,oil pressure,amp,water temp.Fuel pressure on the cowl.Trans/oil temp on the overhead.The primary function of this project is towing and as much info as I can plum in is critical.

[MrJames]

Gary

If I knew that the transmission was heating up to 210 or a little more constantly without undue loading I would be very concerned. I chose 230 on the output side to answer brokenwrench's question of "when to pull over" for a particular spike point due to specific conditions. Again, at that temperature it may have already burnt the fluid and caused additional damage.

I still wonder if the return temperature would be "normal" if that 230 output was occurring. Would I assume that all is well because my cooler(s) are very effectively returning 190 or 200 degree fluid in that state ?

I also understand that below normal temperature is just as bad as overheating.

I would love to hear your results if you do install two switched sensors.

[MrJames]

Brokenwrench

I believe that if was getting a 230 degree return temperature with functioning cooler(s) that the transmission would have already made the decision as to when to pull over.

I still wonder what a temperature sensing gun would reveal if the pan, out and in lines as well as the pressure port were measured and compared.

There is no doubt in my mind that cutting in sensors can cause problems. If the port works then why ask for trouble ?

[MountainManJoe]

I wouldn't be too concerned about 230 deg F (or 110 C) coming out of the tranny at all. In fact I think that could happen very easily. Especially towing. Especially uphill. I reached that temperature in my pan taking a rough road (a lot of TC slippage). And that's with a 28,000 BTU aux cooler. It's not great for the lifetime of the fluid, and it's when I pull over for a bit, but it's not that bad for the tranny if you don't keep it up.

I also understand that below normal temperature is just as bad as overheating.

I disagree with this.

[MrJames]

Right on timelessbeing

The entire concept here is in or out temperature. If in then 230 is a real problem. If out then much less but a need to rethink your actions.

[MountainManJoe]

If in then 230 is a real problem.

I'm not sure what you mean by problem. Depending on your driving habits, It CAN get this hot in extreme situations, like off-roading or pulling out a stuck vehicle in hot weather. Just don't overdo it, but ATF is surprisingly durable.
MAYBE you could keep temps within spec in any situation with dual aux-coolers with fans or somethin, but would you really want to go through all that just for those rare occasions?

[MrJames]

timelessbeing; Let me begin by saying that I agree with everything you have stated except the too low a temperature opinion. I do believe the cooler side of the operating temperature range is better for the life of the system.

The theoretical "problem" that I am speaking of is that by measuring on the return line and detecting a fluid temperature of 230 degrees returning from functioning cooler(s) would indicate that a much hotter temperature was exiting the transmission. Heaven forbid if that was with dual or triple coolers.

I believe that if this happened and you became aware of it in this manner (return line measuring) it may be too late for the transmission.

[brokenwrench]

"too cool" only affects seal performance. reaction times in clutch packs and accumulators would be slower, rather like running 90w in your engine. I have been told that in extreme cold in the far north of Canada they use ethylene glycol in transmissions, rather than hydraulic fluid. current recommendations from manufacturers are that you do not have to warm up anything, start and go. this is bullshit. their problem is that there is such better manufacturing now that vehicles would last 25 years with a little warmup and spec maintenance. not good for the big three. 320 degrees I would be worried about, 230 is not really a big deal. I often see off shore rebuild kits for a third of the price of domestic kits. something has to be compromised. probably make the seals out of recycled running shoes.

[1Gary]

Technically you could run the B & M cooler with the fan on a thermostat to turn on the fan at a temperature.

[oldsmoker]

wow!...this turned out to be quite the topic!....im loving the exchange of experience here!...thank you!