Re: allison mh4000 trans
rhall - 9/25/2009 4:57 PM
i drove the mh about 50 miles today .i drove it at about 85 mph up and down some hills the temp on the monitor showed 227 when i stopped and checked the to cooler line at the trans it was 187 the temp at the from cooler line at the trans were the sender is it showed 204 with the laser do you think it will be ok . can the sump j1939 link be wrong
The temperatures you're quoting don't indicate a problem in and of themselves. What makes no sense is you're reading the from cooler higher than the to cooler, and the sump is higher than both.
I can believe the J1939 CAN signal for sump temp that goes to the screen might have something throwing it off, but the to cooler oil being cooler than the oil that has passed through the cooler is unusual.
I double checked the hose locations. To cooler is the left port as looking at the rear of the trans. From cooler is on the right. Your plumbing makes sense for a side tank cooler(side tank attached to the engine radiator). The to cooler goes in the bottom of the tank, which pushes any air out as the oil flows in. The from cooler comes from the top of the tank back to the trans.
If this vehicle were mine, I'd put some manual gauges in both those cooler ports and get some very accurate readings of what's going on there. If the to cooler oil really is cooler than the from cooler oil, that would mean the engine water is hotter than the trans oil and is actually heating the trans oil. But "heating" it to 204 degrees is still well below the max temp for the trans. However, that still leaves the question of why the sump is hotter than both unanswered.
I assume, because you haven't mentioned it, there's no output retarder on the transmission and you don't see any foaming of the oil on the dipstick.
Another thing I'd do if it were mine is put a temperature probe for a manual gauge in a fitting that adapts to the drain plug hole. That would verify what the sump temperature actually is. I'd be surprised if the sump really is hotter than both the to and from cooler oil.
You may not want to go to all that trouble or expense because the temperature values you are quoting do not indicate temperatures that are over any published maximum.