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Topic: Very Jerky Allison Trans (Read 563 times) previous topic - next topic

Very Jerky Allison Trans

Test driving a U240 with Cat 3116 and Allison 6 sp. this morning, the shift was so jerky I parked and did not want to continue driving. The coach sat for 2-3 years unused, but on this test drive the coach was all warmed up and seemed ready.
There was a "1" code on the shift pad in Drive.

Any thought would be helpful.

Re: Very Jerky Allison Trans

Reply #1 –
First thing I would do is check fluid levels and go from there.

Re: Very Jerky Allison Trans

Reply #2 –
Use the shift pad to check for transmission DIAGNOSTIC CODES.

Ignition on (engine off)
Press the up and down arrows at the same time.  If that brings up d-1, you are in diagnostic codes.

If it brings up OL, press the up and down arrows again to bring up diagnostic codes.

After the d-1, there will be two digit pairs of any diagnostic codes.

Press the mode button to go to d-2, 3, etc.

When there are no more diagnostic codes you will see d- "the number" followed by - -.

Let us know what you find.  Could be as simple as low voltage to the Allison ECU.

Re: Very Jerky Allison Trans

Reply #4 –
Quote from: wolfe10 –
Use the shift pad to check for transmission DIAGNOSTIC CODES.

Ignition on (engine off)
Press the up and down arrows at the same time.  If that brings up d-1, you are in diagnostic codes.

If it brings up OL, press the up and down arrows again to bring up diagnostic codes.

After the d-1, there will be two digit pairs of any diagnostic codes.

Press the mode button to go to d-2, 3, etc.

When there are no more diagnostic codes you will see d- "the number" followed by - -.

Let us know what you find.  Could be as simple as low voltage to the Allison ECU.
Brett,

Thanks. I am going to save your instructions for future use, as I dropped the coach off at Western Caterpillar this morning to have them diagnose; there was also a fluid leak I couldn't pinpoint as well, and I am having them change oil and all of the filters.

Also, please disregard my comment about the code while underway, as I was unaware that the later shift pads displayed the gear in the window where a code would be on the earlier models.

While we're on the subject, does the CAT 3116/Allison setup on the U240 have a diagnostic reader port that uses a reader similar to the Prolink 9000 or some OBD-II scanner?

Re: Very Jerky Allison Trans

Reply #5 –
You could call 501 955 3880... Dwight.  He is the oldest and best I've seen with the earlier Allisons in particular. He is on central time and is very generous with his time. You may very well find your issue by following the code procedure Bret mentions but if not..

Re: Very Jerky Allison Trans

Reply #6 –
Quote from: RandallBrink –
While we're on the subject, does the CAT 3116/Allison setup on the U240 have a diagnostic reader port that uses a reader similar to the Prolink 9000 or some OBD-II scanner?
I don't know about the CAT engine, but it seems the transmission might provide a DDR (Diagnostic Data Reader) connector.
See Figure 1-1 on Page 7 of the manual linked below.  It mentions using a Pro-Link diagnostic tool J 38538-A to read data.

General Description; Transmission; Electronic Control Components View -...

https://ww2-secure.justanswer.com/uploads/HE/HeavyEquipmentTech/2013-09-22_223029_allison_transmission_md3060_trouble-shooting.pdf

Re: Very Jerky Allison Trans

Reply #7 –
Quote from: Chuck & Jeannie –
I don't know about the CAT engine, but it seems the transmission might provide a DDR (Diagnostic Data Reader) connector.
See Figure 1-1 on Page 7 of the manual linked below.  It mentions using a Pro-Link diagnostic tool J 38538-A to read data.

General Description; Transmission; Electronic Control Components View -...

https://ww2-secure.justanswer.com/uploads/HE/HeavyEquipmentTech/2013-09-22_223029_allison_transmission_md3060_trouble-shooting.pdf
Thank you—this looks like it will answer the question about diagnosing issues and codes.

Re: Very Jerky Allison Trans

Reply #8 –
But, you can check for diagnostic codes for FREE from the driver's seat.

Sure, you may need more in-depth diagnosis, but start with the free stuff.

Re: Very Jerky Allison Trans

Reply #9 –
Quote from: wolfe10 –
But, you can check for diagnostic codes for FREE from the driver's seat.

Sure, you may need more in-depth diagnosis, but start with the free stuff.
Brett,

Yes, from what you have described in terms of codes that can be gotten from the pad—that is probably more than enough for me, whereas anything more involved would require service.

Re: Very Jerky Allison Trans

Reply #10 –
The other thing that you can easily check is that the transmission's throttle position sensor is not disconnected/cable broken.

Easily seen once you raise the bed.

Re: Very Jerky Allison Trans

Reply #11 –
Quote from: wolfe10 –
The other thing that you can easily check is that the transmission's throttle position sensor is not disconnected/cable broken.

Easily seen once you raise the bed.
Very good call, I didn't think of that. Earlier I dropped the coach off at the Caterpillar shop to have them do the fluid and filter service and chase down a fluid leak that I couldn't find. I also wrote up the hard shifting from 1st to 2nd, so they will probably find the throttle position sensor problem if that's what it is, and now that you mention it, that's what it felt like is non-responsive to throttle position.

Re: Very Jerky Allison Trans

Reply #12 –
I found a broken cord right beneath the control room which may well turn out to be the throttle position sensor.IMG_1179.jpg

 

Re: Very Jerky Allison Trans

Reply #13 –
Snake, Snake, Snake...