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High Trans Temp
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Dick,
We also don’t have a transmission temp gauge on the dash. What we have is a coumpter readout in the info section. I have to toggle through a couple of screens to see the trans temp. It seems to stay steady at 207.
Mark
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Generally the transmission temperature on XL coaches or H models of that vintage will track the engine temps closely (except in rain which causes a drop in temps) but if a retarder is installed and active the transmission temps can climb significantly when the retarder is engaged or brakes are being used. This is (I think) due to the temperature sensor downstream from the retarder, but ahead of the intercooler.
On XLII or H models of that vintage the temperature sensor has likely been relocated because the transmission temperature readout (on the message center) no longer reacts to the use of the retarder but more closely reads the same or close to engine temp.
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DICK: My coach is kind of a bastard because it has the XLII dash which displays engine oil temp as a selected display. I’m with Jon; your coach probably has a ddec sensor. I’ve never seen excessive engine oil temps although I do not monitor them constantly and I agree coolant will be more critical. I DO have trans oil temp as my default display and it IS critical with a retarder.
My coach had 4 round 2 1/16″ gauges located on an angled panel high to the driver’s left. They were the two voltage gauges and 2 generator gauges. My gen gauges have been relocated (Dakota Digital) to the central electrical panel as I rarely use gen while driving (OTR equipped). I have replaced those 2 gauges with 2 1/16″ round analog VDO diff temp and outside air temp. You will probably be surprised by your diff temps. Full synthetic oil helps; removal of the full width rear mud flap helps, and I’ve gone to super singles on the drive for airflow over the brakes. I still find it necessary to occasionaly reduce speed under adverse conditions to maintain diff oil temps below 275F but I’m often running at 110F+ ambient pulling 20,000#.
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A concern I have is that on XL and H vintage coaches that do not have a message center the information was via the small round gauges. My concern is none are marked for limits. Some limits we know. We know what temps the fan clutch engages on the high and low speeds. We know at a certain coolant temp we get a CEL. But do we know the upper and lower limits for oil pressure? Do we know the upper limit for the transmission fluid?
Voltage? Boost? Differential temp? Air pressure upper limit?
None of those are redlined on any of the gauges. How about engine RPM? Not redlined.
We do know DDEC and ATEC will protect us from exceeding some limits. At least I think they will. But I for one would like a mark on the gauge that shows the upper limit. Does anyone know if Joel’s differential temps are within an allowable range? There is not a shred of infomation on the Prevost web site about that. We are assured if the retarder heats the fluid to 300 degrees it will back off to limit the fluid temp to 300, but a marking on the gauge to show us when nearing a limit would be helpful.
I wish our coaches came with an owner’s manual page that listed limitations. We have a page full of limitations once we start digging into that, with all of the lmitations coming from all sorces and for many reasons.
Why can our coaches go faster than the 75 MPH speed limitation for the tires? Why do we need to rely on an unreliable device (the Vanner electrical monitor) to light a warning light to tell us we are over voltage? or out of balance. Wouldn’t two gauges, one for 12 volts and one for 24 volts with proportional scales that would show both needles in the exact same spot and marked with the voltage limits be better?
With today’s technologies we would know if our axle weight limits are being observed by translating air bag pressure to a value for the weight carried. The message center could easily be retrofitted and better than just displaying raw data it could not only display temps and pressures, it could also show where within the acceptable range they could be.
I’ll step down off my soap box and go get my meds now.
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I just made a trip to Daytona and back, pulling my stacker with 2 cars inside. My trans and engine temp were no higher than pulling my toad. LONG hills, is the only time I see trans temp rise.
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