Transmission Overheating
Apologies in advance for the rambling nature of this report, but such is my demeanor after spending a day babying my sick coach.
Well, things took a turn for the worse today when after a short, hour and a half drive from West Yellowstone, MT, north on US 191 to Bozeman, everything went very well. The road was mostly flat and the speed was under 60 most of the way. Then, upon arriving in Bozeman, I got the "DO NOT SHIFT" light and had to stop and restart the coach to move it. I limped into a parking lot and along the way my SilverLeaf systems monitor indicated a transmission temp of 281 degrees. The trans temp gauge on the dash, however, showed normal, less than 200.
I checked the fluid and the level seems too high, also, there are bubbles on the stick. According to Allison, high fluid levels can cause aeration of the fluid, and overheating problems. Hmmm. I've never added a drop since it was last changed, 20,000 miles back.
The fluid is TranSyn and was changed a year ago last July when I posted in this same forum when the tranny got stuck in 4th gear, due to my overuse of the retarder on a few long downhills going into Flagstaff. Well, I've since driven about 20,000 miles and always baby the retarder and watch the Trans Temp gauge like a hawk. Never a problem until l10 days ago got a bit too hot on another long downhill in Montana and it went into 4th -only mode again, but only for a short while until the things cooled.
There has been additional odd behavior. Two weeks ago when I was pulling out of a spot where we had been sitting for 10 days, the drivetrain made a loud gear THUNK when I first put into gear. It was alarming but everything seemed normal and it didn't happen again, until this morning when again the coach at for 7 days. This morning, when the coach first started to move, another loud gear THUNK. As before, the coach ran and drove fine, that is until we reached our first stop, in Bozeman.
While maneuvering into a parking spot in Bozeman, another loud thunk as I was pulling away from a stop light.
After a 90 minute shutdown in Bozeman, the temps had fallen to 140 or so (according to the SilverLeaf) and so we took off. In about 15 miles, it had already reached 245 so we pulled off at a rest stop and while coasting into a parking space, we got DO NOT SHIFT again. We're headed for Billings now, 150 miles away, to the nearest Allison shop.
Since the first rest stop, we've been driving about 20 to 40 miles at a stretch, watching the temperature, and limping our way to Billings at 45 to 55 mph. The speed doesn't seem to have much of an effect in the temperature rise, but climbing hills does cause it to go up quickly. I turned off the retarder before we left Bozeman and haven't used except for one time, just to see what happened. Well, it had next to no effect. I would guess that this was because the hot oil has nearly zero viscosity left. Throughout all of this, the dash temperature gauge still shows normal readings. The engine temperature has been steady as a rock, hovering around 195.
We're about 50 miles out now. Most of the passes are behind us. The last pass spiked the temperature to 302 degrees, but oddly, the ECU didn't shut down the tranny and we pulled into a truck stop with no apparent problems or odd noises, shift hesitations, nothing. Everything seems fine except for the digital temperature. One final note, the transmission cools best with the engine sitting parked in idle.
We're hoping to make it to Billings this afternoon, in one or two more hops. We'll be spending the night in the Allison parking lot and the service guy has already informed me that there is no guarantee that he'll get to us tomorrow. So, it's looking like a little unscheduled vacation in Billings is in store for us.....
By the way, I can accept that the tranny is blown, but what I'm most eager not to experience is a towing. I'll be pretty happy just to make it this last 50 miles.
-fred
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Gary & Lise Deinhard, 2003 Elegant Lady Liberty, Dbl slide
Originally Posted by BoaterAl
