[Chester Stone]

Yes, fast idle is best.

[folivier]

And with the rear radiator you need to keep it clean. It sucks up road grime and anything spun off by the engine and clogs up the radiator, especially if driving on wet roads.

[Fulltiming]

Based on today's drive, I will also add that a strong head wind can also result in higher transmission temperature because it may not let the transmission lock up.

I was seeing temperatures of 215 degrees, if you believe the transmission temperature gauge and lower fuel mileage than normal.

[Chester Stone]

Like I posted before, I have seen transmission temperatures of 240-250 with no known damage. I use synthetic oil in the transmission.

[Fulltiming]

I changed out to TranSynd a couple of years ago also.

[77newell]

Michael: if you have the HT741 transmission it will lock up in 2nd gear some time after shifting into that gear but before shifting to 3rd. Once it locks up in 2nd it stays locked up until downshifting. 3rd and 4th gear are always in lockup. The shifting sequence is 1st unlocked, 2nd unlocked, 2nd lockup, 3rd lockup, 4th lockup

I suspect your higher temperature is due to the higher load passing through the gears in order to maintain speed against the resistance of the headwind. Even more likely is that the increased load due to headwind increases the engine load and coolant temperature which raises the transmission oil temp as that oil passes through a coil in the bottom of your engine coolant radiator (assuming your coach works the mine does). With that arrangement, any rise in engine coolant temperature will likely cause a rise in transmission oil temp. I've noticed that correlation with mine. A reason for this configuration is to get and keep the fluid warm to reduce viscosity so there is less oil drag in the transmission and ergo better fuel efficiency. What will they think of next?

[Fulltiming]

I believe mine is the HT 740 (I also have the Stone Bennett air shift) rather than the HT 741. However, I don't know what differences there are between the two but I do notice the lock up in 2nd gear which at times almost feels like another shift. I do not recall that lockup in other gears so mine likely has the same characteristics and I agree that the increased transmission oil temperature is likely the result of the increased load rather than an unlocking in 4th gear. I do appreciate that information.

Today I had a tail wind instead of a head wind and at the same ground speeds I was seeing significantly lower transmission temperatures (20-40 degrees lower) while engine coolant temperature was only down about 10 degrees. I was also getting about 1-1.5 mpg better fuel economy which is to be expected.

Chester, I agree. I don't think that even with the head wind, the temperatures I was seeing were an issue.

[77newell]

I should have noted in my post that all Allison 700 series 4 speed transmissions have the same shift pattern whether they are mechanical or electronic. Yes, the lockup kicking in does feel a lot like a shift.

If you want to check to see which version, electronic or mechanical, you have, just look under the coach at the passenger side of the tranny. There will either be a mechanical shift mechanism or a big honking electronic cable connector. Both transmissions work really well. The singular advantage of the electronic version, IMO, is some flexibility in programming how it operates, something almost none of us will ever use.

[Fulltiming]

Mine is mechanical, operated by the Stone Bennett air shifter.

[77newell]

Michael: yeah I got that yours is mechanical though I'm surprized since the electronic was available. Then again, maybe I should be surprized that mine is electronic.

Anyway, I posted mainly to make it easy for others in case they were unsure and wanted to check in case it wasn't obvious from the selector which can be either lever or pushbutton.