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Transmission Shift Problem
Its a long story but try and bear with me here. We left last Tuesday from Indianapolis to go to Louisville to the NSRA Street Rods Nationals. It was my first time pulling a 24 ft encolosed trailer with the bus.I did every preflight inspection possible to ensure a good safe trip. My hitch is a 20K hitch/1500 tongue weight which is way over and above what I need. The electric brake control was replaced with a new one, etc. The rig is too long for me to get out of my driveway all hooked up so took the bus to a local school parking lot and my son brought the trailer to me and hooked up there.
We left and all was well. I turned on the tranny retarder and it was working fine as well. The first 83 miles of the trip was uneventful. At 83 miles ran into some heavy traffic on southbound I-65.
Sat in stop and go traffic for nearly 30 minutes. When the traffic cleared up I began to accelerate and the bus suddenly downshifted and lunged really hard. So hard we thought we had been hit. The tranny started shifting eratically up and down between 3-4-5th gears. I slowed down, checked and the retarder switch was in the “on” position. I turned it off and the shifting after about a half a mile smoothed out. Tranny and engine temps were normal.
Stopped about 20 min later for fuel. Since we were already close to the fair grounds the bus only went two more complete 1-6 gear shift cycles after the fuel stop. Both of those shift cycles were a little rough but I didn’t really think too much of it. Dropped off the car trailer in the designated area at the fairgrounds, spotted the bus at the campsite and had no further issues.
Spent 5 great days at the event and it was time to leave last night. Pulled the bus off the camp site with no problems, had N-D-R idle and fast idle all good. Left the fairgrounds with a short distance to get on northbound I-65 and sure enough first cycle of the transmission shift of 1-2, 2-3 were eratic again. I was at the entrance ramp to the interstate, it was either get on or go thru a neighborhood so I figured once I got into 6th gear, (like on the waydown) all would be good.
Once I tried to accelerate with merging traffic the transmission shifted one time (1-2) and would not up shift. I stayed in the right lane running 2100 rpm in 2nd gear (which is 28mph) watched the engine/Tranny temps which stayed normal until i crossed the JFK bidge and could find a large parking lot.
Pulled into a Walmart lot, went to put the bus in neutral and the entire keypad was unresponsive. It still showed “2”. The only digital response I could get was the mode button which was of no help.
The idle was normal so I set the parking brake and went back to check the transmission fluid. It appeared to be ok, a little hard to read on the stick but it appeared wet up to the mark.
I felt I was at an impass. Here I set, 75ft long in a crowded Walmart lot with a tarnsmission stuck in gear and no reverse. I thought about shutting the bus off to see if everything would reboot, My hotrodder instinct fter all, the bus already proved it would run 28mph with no issues.
Set the 4 way flashers and off we went. Lucky for us there was no traffic. Other than the extreme bordum of a 5 hour drive at 28mph we made it home. Unhooked the trailer in the school lot. and for the first time ever had to pull the bus into the driveway. (Not an easy task off of an old county rd with a keypad that would not allow me to back up and square up at least once).
Once I was in my own driveway when I shut to bus off I waited a minute and turned the key back on. The shift pad lit back up as normal. I had N-D-R, 1-6 and also had fast idle when I selected it.
My son suggested that since it was 3am it would be a great time to go ahead and turn the bus around and get it in the building which is what we did.
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So, I’m sorry for the rambling on in the above but working in aviation, having accurate facts leading up to troubleshooting is always crucial.
Has anyone else experienced something like this?
My guess is my problem is electrical, say maybe a solenoid?
Does anyone know of an Allison transmission hotline I can call ?
Is there a master reset button that might cure my problem?
I know the fix is more than likely above my paygrade but I want to go into this with my eyes open so I can try and mitigate the repair bill some.
Also, what are the thoughts about my ignorance of forgetting to switch off the master retarder switch on the trip going down? Is it possible this was the root cause of my problem?
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6 Replies
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John,
A lot of your questions are beyond my pay grade, but I do know some things from experience.
There was a vintage of transmission around the model year of yours that had an issue with the wear of the clutches. That clutch wear affected shift quality. Whether that is contributing to your problem might be revealed when an Allison dealer does the test. The will hook you up to a computer and your transmission will be analyzed down to how much clutch wear you have. Some clutches had such wear the material that wore off contaminated the transmission because it was so much.
You should always check your transmission fluid level on the key pad. hit the up-down arrows simultaneously and after a countdown the key pad display will tell you if it is OK, or low or overfilled. The tranny has to be at operating temperature. I believe the codes for the display can be found at the Allison web site. They might also reveal if the transmission had any codes while acting up
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John,
I keep my Retarder master switch “ON” all the time, so it is ready when I need to apply it with the Stalk control. I also pull a Stacker at times, with no issues.
I do have my brakelights disabled when using the retarder, so the brake lights do not come on when using the retarder, only the brakes, or parking brake. That way, you are not constantly applying trailer brakes every time the retarder comes on.
Don’t know if that may be a cause of your problem or not.
I would drive it without the trailer, and see if all is well, if so, Check how the brake controller was wired up.
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John,
There’s alot of years between our buses but you are describing the symptoms of a input trans speed sensor. Acting erratic like that happened to me and it was the sensor. I don’t have a clue to the differences in mine and your transmission but Prevost or Allison can tell you in 5 mins when they plug in.
Later
bv -
Thanks for the heads up and all the advice. The one thing that I did not mention is the bus has 119,000 miles on it.
It was kind of freaky, we bought the bus at Panterra last winter and there was no objective evidence left behind of previous ownership. Because of this they had to zero our most of the preventive maintenance (Fluids, filters a couple of norgens to correct air leaks) While at the campground at the NSRA event we met the previous owners. I did ask about any engine/transmission issues and they said they had none.
Keep your experiences coming my way. I’m always skeptical of dealing with technicians until they have proven their worth and knowledge to me either by trusted word of mouth or sucessfully fixing a previous problem for me.
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I’m with Bernie John, speed sensor.
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Thanks guys.
Another thing I forgot to add was the “Do Not Shift” light was on the entire time the transmission was stuck in second gear.
It too went out once I turned the engine off and everything rebooted.
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