Intermittent trouble downshifting with WOT

[elebouef]

Itasca Meridian 34B 340 Cummings Allison MH2500. Have Intermittent trouble downshifting climbing a grade or trying to pass. Sometimes unable to down shift unless down arrow is pushed many times. Will go into limp mode after making a manual downshift and then pushing the up arrow to 6 then stop at a stop sign. Replaced all 3 speed sensors and no change. Key pad will not read out trouble codes nor does the mode function work.

Has anybody had this problem?

[sstgermain]

I never manually down shift. I let the transmission and engine decide when it needs too.

[wolfe10]

Not "choosing to" manually downshift is VERY DIFFERENT from the transmission not being able to do it as it should.

Yes, ASSUMING this is a significant change from "what it was"/"what it should be".

[dickandlois]

3 hours ago, elebouef said:

Itasca Meridian 34B 340 Cummings Allison MH2500. Have Intermittent trouble downshifting climbing a grade or trying to pass. Sometimes unable to down shift unless down arrow is pushed many times. Will go into limp mode after making a manual downshift and then pushing the up arrow to 6 then stop at a stop sign. Replaced all 3 speed sensors and no change. Key pad will not read out trouble codes nor does the mode function work.

Has anybody had this problem?

Welcome to the FMCA Forum !

  What is the model year of your coach?  Do you have any transmission issues when up shifting?  Have you had the transmission control module software scanned? Has the shift pad registered and or stored any error codes? 

Rich.

[bm02tj]

The program is set to not down shift so the motor will be over speed when shift complete so will not down shift 

 

when i hit a long hill I will select the gear to hold it after it shifts down its self 

[wildebill308]

5 hours ago, elebouef said:

Itasca Meridian 34B 340 Cummings Allison MH2500. Have Intermittent trouble downshifting climbing a grade or trying to pass. Sometimes unable to down shift unless down arrow is pushed many times. Will go into limp mode after making a manual downshift and then pushing the up arrow to 6 then stop at a stop sign. Replaced all 3 speed sensors and no change. Key pad will not read out trouble codes nor does the mode function work.

Has anybody had this problem?

Welcome to the forum. 

What speed and rpm are you running when you try to downshift?

Bill

[elebouef]

3 hours ago, DickandLois said:

Welcome to the FMCA Forum !

  What is the model year of your coach?  Do you have any transmission issues when up shifting?  Have you had the transmission control module software scanned? Has the shift pad registered and or stored any error codes? 

Rich.

its a 2013. No issues up shifting. I don't know if the Allision tech scanned the module. No error codes have ben set in the TCM but I did get a code alarm.

Thanks

Ed

1 hour ago, WILDEBILL308 said:

Welcome to the forum. 

What speed and rpm are you running when you try to downshift?

Bill

Anywhere between 45 and 55

Thanks

Ed

4 hours ago, sstgermain said:

I never manually down shift. I let the transmission and engine decide when it needs too.

 

[rsbilledwards]

I manually down shift all the time to use the jake all the way to first and have never had/have a problem  Allison 4060 

[dickandlois]

Ed, This Allison information might help you run some tests and reset the transmission. If the the problem still happens. It might offer some helpful tests or a solution.

http://www.rvtechstop.com/resources/Articles/allsonok.pdf

Rich.

AllisonMECHANICSTIPS_1000_2000_Series.pdf

[manholt]

I downshift my 3000 manually, in/off cruise control, up or down steep grades and have had no issues. The idea is to keep high rpm's.  If you don't downshift, you risk "lugging" the engine...that's not a good idea!  

[sstgermain]

9 hours ago, bm02tj said:

The program is set to not down shift so the motor will be over speed when shift complete so will not down shift 

 

when i hit a long hill I will select the gear to hold it after it shifts down its self 

That is exactly how my Journey used to operate and that is how my Tour operates.

[elebouef]

8 hours ago, DickandLois said:

Ed, This Allison information might help you run some tests and reset the transmission. If the the problem still happens. It might offer some helpful tests or a solution.

http://www.rvtechstop.com/resources/Articles/allsonok.pdf

Rich.

AllisonMECHANICSTIPS_1000_2000_Series.pdf

Rich, thanks for the info. My keypad (the same as displayed) does not function exactly the way rvtechstop describes the functions. The mode button does not work and the display for economy is not lit. I am unable to enter the diagnostics by pushing the up and down arrow keys and this going into limp mode really scares if I don't catch it as the engine is doing 3200 RPM before I know it.

Ed

[sstgermain]

That might be the Winnebago has the transmission programmed. My Journey never was able to go into an economy or a mode light come on.

[elebouef]

1 hour ago, sstgermain said:

That might be the Winnebago has the transmission programmed. My Journey never was able to go into an economy or a mode light come on.

Thanks Steve, that may be true. I'll try calling them and see what they say.

Ed

[wolfe10]

Ed,

Any Allison dealer can verify programming and if incorrect, change it.

BUT, if this is a recent change (vs it has always shifted this way), it is unlikely to be the ECU programming.

I have no first hand experience with the 2500 (only 3000 and 4000) but wonder if an Allison dealer can check for codes (like we do on the 3000/4000 with the shift pad)?

[elebouef]

1 hour ago, wolfe10 said:

Ed,

Any Allison dealer can verify programming and if incorrect, change it.

BUT, if this is a recent change (vs it has always shifted this way), it is unlikely to be the ECU programming.

I have no first hand experience with the 2500 (only 3000 and 4000) but wonder if an Allison dealer can check for codes (like we do on the 3000/4000 with the shift pad)?

Thanks Brett, I did have it at the Allison dealer for this problem and they said it was one of the 3 speed sensors but didn't know which one so they replaced all 3 for a cost of $50 for parts and $450 labor and misc. shop charges. Needless to say I'm a little nervous to take it back to them.  

[dickandlois]

Ed, Some interesting feedback.

This is some Kick down information for your trans.  2500 MH Trans is a four speed with OD.

3.6 KICKDOWN Some vehicles have a “kickdown” feature that allows the operator to choose between an “Economy” primary shift schedule and “Performance” secondary shift schedule. The throttle pedal will have a detent feel when full­throttle is achieved using “Economy” shift points. When the operator “steps through” this detent, the function is activated and “Performance” shift points are achieved.

There might be an issue with the throttle point on the pedal, to activate the performance shift point. 

You might also run the manual ECM codes  with read out switch's.  They are most often located under the dash, near the steering column.

3.9 RANGE INHIBIT(ED) LIGHT The red or amber RANGE INHIBIT(ED) warning light is located on or near the shift selector. The purpose of this indicator is to alert the operator that transmission operation is being inhibited and that range shifts being requested by the operator may not occur. When certain operating conditions are detected by the TCM, the controls will command the transmission to be locked in the range currently in use. If the torque converter clutch is applied when the condition is detected, the clutch will be disengaged concurrently with the activation of the RANGE INHIBIT(ED) light. Each time the engine is started, the RANGE INHIBIT(ED) light will illuminate, then turn off after two seconds. If the light does not illuminate during ignition, or if the light remains on after ignition, the transmission system should be checked immediately. For the conditions under which shift inhibits occur, see the SHIFT INHIBITS section in this manual.

Over Range sounds like the issue - you are reaching 3200 plus RPS at the point the engine is limited to 900 RPS - Limp Mode.

Rich.

The (MAP) manifold absolute pressure sensor senses engine load through pressure in the intake manifold. A faulty MAP sensor will really affect engine performance, but can also affect transmission's shift timing. This is because the PCM uses this signal as an indication of engine load.

[elebouef]

1 hour ago, DickandLois said:

Ed, Some interesting feedback.

This is some Kick down information for your trans.  2500 MH Trans is a four speed with OD.

3.6 KICKDOWN Some vehicles have a “kickdown” feature that allows the operator to choose between an “Economy” primary shift schedule and “Performance” secondary shift schedule. The throttle pedal will have a detent feel when full­throttle is achieved using “Economy” shift points. When the operator “steps through” this detent, the function is activated and “Performance” shift points are achieved.

There might be an issue with the throttle point on the pedal, to activate the performance shift point. 

You might also run the manual ECM codes  with read out switch's.  They are most often located under the dash, near the steering column.

Rich.

Hey Rich, my 2500 MH is actually a 6 speed. I did connect a code reader but there were no trans codes set and I was able to see many different trans. parameters. There was 1 engine code, SPN 102. That code has set 4 or 5 times but nobody seems to think it's a problem.

[dickandlois]

Allison list it as 2500 MH Trans is a four speed with OD.   So the coach builder must have requested an option for a 6 speed setup.

Ed, The 102 code is a intake manifold - pressure sensor code. Reading is ether high or low. In the Cummings  error code  and is at a level 2 code. It has thrown this code 4 to 5 time. 

A level 2 code  has a fix when detected rating - A level 3 is fix at the next oil change and maintenance. Level 4 is just information - no work required.

A level 1 code is shutdown the engine code.

The sensor is around 50 to 60 dollars. Labor ?

No info regarding the manifold pressure or flow, but if it works like a map sensor - engines with a low or restricted air flow do not work to well.

Have you looked at the air intake system components for any openings, restrictions or dirty air filter? 

Rich.

https://www.amazon.com/Cummins-2897334-Manifold-Pressure-Temperature/dp/B0734CDMX5

[elebouef]

2 hours ago, DickandLois said:

Allison list it as 2500 MH Trans is a four speed with OD.   So the coach builder must have requested an option for a 6 speed setup.

Ed, The 102 code is a intake manifold - pressure sensor code. Reading is ether high or low. In the Cummings  error code  and is at a level 2 code. It has thrown this code 4 to 5 time. 

A level 2 code  has a fix when detected rating - A level 3 is fix at the next oil change and maintenance. Level 4 is just information - no work required.

A level 1 code is shutdown the engine code.

The sensor is around 50 to 60 dollars. Labor ?

No info regarding the manifold pressure or flow, but if it works like a map sensor - engines with a low or restricted air flow do not work to well.

Have you looked at the air intake system components for any openings, restrictions or dirty air filter? 

Rich.

https://www.amazon.com/Cummins-2897334-Manifold-Pressure-Temperature/dp/B0734CDMX5

Rich thank you so much. I will get that sensor ordered. I just changed the air cleaner and there is no restrictions in the induction system so it must be that sensor.

Ed

[manholt]

The factory must  have changed the amount gears from 4 to 6.  I only had one 2500, it was 4 speed with OD, mated to a Duramax engine in a 2500 Silverado! 56,000+/miles, never an issue, no matter what I pulled...I also used it as a toad.