Weird Allison Glitch

[bruceh]

After driving most of the day to get home, I was braking and downshifting to stop at the last signal before my house. As I downshifted, I noticed no change in engine revs but was smelling the barn and didn't connect the dots.

When the signal changed, I pushed the gas and it acted like I was in neutral, actually rolling backward. I tried several gears with no effect. I turned the engine off and restarted it and drove away like nothing had happened.

Has anybody else had this or heard of it???? The lack of engine braking earlier in the day could have been a crisis as I was driving across a mountain range.

The trans was changed over to Transynd last March and the trans temp was about 140

[DAN L]

Quote:

Originally Posted by bruceh After driving most of the day to get home, I was braking and downshifting to stop at the last signal before my house. As I downshifted, I noticed no change in engine revs but was smelling the barn and didn't connect the dots. When the signal changed, I pushed the gas and it acted like I was in neutral, actually rolling backward. I tried several gears with no effect. I turned the engine off and restarted it and drove away like nothing had happened. Has anybody else had this or heard of it???? The lack of engine braking earlier in the day could have been a crisis as I was driving across a mountain range. The trans was changed over to Transynd last March and the trans temp was about 140

is the fluid level ok when hot?

[bruceh]

The fluid was a little low. The Allison techs could not find any codes.

Oddly, it took 4 guys to get the diagnostic computer to sync up with the onboard computer and they never were completely successful. They offered to remove my computer and take it into their bench computer, I declined.

[bruceh]

I figured out why they could not connect to my computer. When they hooked up their test computer, they blew the 10a data fuse.

My scangauge was not working after they worked on the coach. I thought that they had toasted my scangauge by hooking it up with the engine running. Not so, they had already blown the fuse.

Scary lack of diagnostic ability.

[suddrethgd]

Have experienced the same situation on several occasions. Discussed same with an Cummins tech at the recent rally in NM. He suggested it could be a problem with the "neutral circuit" going to the transmission. Apparently, this circuit tells the transmission it is in neutral. Have not yet persued this with Allison but plan to do so.

[suddrethgd]

Quote:

Originally Posted by bruceh After driving most of the day to get home, I was braking and downshifting to stop at the last signal before my house. As I downshifted, I noticed no change in engine revs but was smelling the barn and didn't connect the dots. When the signal changed, I pushed the gas and it acted like I was in neutral, actually rolling backward. I tried several gears with no effect. I turned the engine off and restarted it and drove away like nothing had happened. Has anybody else had this or heard of it???? The lack of engine braking earlier in the day could have been a crisis as I was driving across a mountain range. The trans was changed over to Transynd last March and the trans temp was about 140

Have experienced the same situation on several occasions. Discussed same with a Cummins tech at the recent rally in NM. He suggested it could be a problem with the "neutral circuit" going to the transmission. Apparently, this circuit tells the transmission it is in neutral. Have not yet persued this with Allison but plan to do so.