Allison 3000 Hesitates When Starting Out - Solved

Assume from your coach signature that you have the Allison 3000 series transmission.

Let's drill down a little more into "what is happening".

When the engine is running and you go from "N" to "D" on the Allison shift pad, what happens? Do you get that slight clunk and if you release the brake does the coach start moving forward? If so, sounds like the transmission is doing its thing properly.

If throttle response is the issue, be aware some engines (do not know what engine you have) DO have a delay when starting out cold to keep drivers from hammering a cold engine.

So:
What engine do you have?
Does this only happen when the engine is cold or all the time?

It only happens when the engine is cold and I am first starting out. I have a Cat C7 engine. When I go from N to D, it moves forward. The issue is with the throttle response. When I push the throttle, it does not speed up. It just keeps going forward at a slow speed. After about a minute, it responds to the throttle normally.

How long after cold start up do you try to move?

Best advice:

Start engine.

After 20-30 seconds, use cruise control to raise idle speed to around 1,000 RPM for quicker warm up.

Do not start driving until temperature gauge starts moving.

If you still have this issue and the temperature gauge has moved off the "cold peg", have a Caterpillar dealer look at it. There were some issues with this, but you do not want to push any stone cold diesel-- hence the poor throttle response was designed in. But, if this feature stays active too long, a Caterpillar dealer can remedy it.

Sounds good. I do warm it up that way but I have not been looking at the gauge. I will get more information when I go out on the next trip.

Have you changed the trans filters or checked the level. Here is the way to check trans when you come in warm and after you get it level. (Checking Fluid Level with the Keypad)
The following procedure will allow you to check your transmission fluid level from inside the vehicle, and it is also more accurate than checking via the dipstick.
To enter the transmission oil level display mode, press the UP and DOWN arrow buttons simultaneously on the mode selector. A two-minute countdown begins when the following conditions are met:
Engine is at idle
Transmission sump oil is at operating temperature
Transmission output shaft has stopped
Transmission is in neutral
Oil level sensor is functioning properly
The display should show *8 and then count down to 0. Note that it will take two minutes to complete this countdown. During the countdown, the display flashes and a count (8,7,6,5,4,3,2,1) occurs reducing by one digit every 15 seconds.
NOTE: Failure to meet any of the above conditions will stop the two minute countdown. The shift selector will then display one of the following Oil Level Codes to show the reason for the countdown interruption. The countdown will resume where it stopped once all conditions have been met. Shift selectors with single digit display will display the codes one digit at a time. Shift selectors with two digit displays will display the codes two digits at a time.
OIL LEVEL CODE
CODE DESCRIPTION
oL 0X
Setting time too short
oL 50
Engine RPM too low
oL 59
Engine RPM too high
oL 65
Neutral not selected
oL 70
Sump fluid temperature too low
oL 79
Sump fluid temperature too high
oL 89
Output shaft rotation detected
oL 95
Oil level sensor failed

After the two minute countdown, the shift selector displays the oil level data as in the following examples:
OIL LEVEL READINGS
MEANING OF READINGS
o, L, o, K
Fluid level is correct
o, L, L, o, 1 or OL, LO, 01
Fluid level is 1 quart low
o, L, H, 1 or OL, HI, 01
Fluid level is 1 quart high

To exit the oil level display mode, press the NEUTRAL button or simultaneously press the UP and DOWN arrows twice.
JR

I just pull the dipstick while it's running up to normal temp (after driving) and check the tranny oil that way. Works fine for any truck with an automatic. My Allison 3000 manual says to do it that way too...

Two points:

The OP is not describing a transmission issue-- more a throttle response issue.

And Allison, in their seminars at FMCA Conventions recommends that the electronic fluid level check is more accurate than the manual one. A lot of that probably has to do with the dip stick and dip stick tube NOT being Allison parts, but chassis maker designed and supplied parts.

Sure, on trucks or any configuration where the dip stick IS Allison supplied, this may be different.

I brought the coach to my local Freightliner shop and found out the issue. The high pressure oil pump (HEUI) was going bad. This supposedly is something that sometimes happens in the Cat C7 engines. The problem is that when it is going, most of the time it puts metal shavings into the oil and into the injectors, requiring that the injectors be replaced.

The engine only has 40K miles on it when I purchased it at 8 years old, it had only 12K miles on it and I did not have past maintenance history records. That is why I purchased an extended warrantee.

This was an expensive repair - $5600. Thank goodness I purchased an extended warrantee when I purchased the coach and they paid for the repair. The warrantee has more than paid for itself at this point and I have about a year left on it.

So if you are having issues with the engine not responding to the throttle, you should go have it checked out. At some point, it would have failed completely and I would have been stuck on the side of the road.

ncrowley wrote:
I brought the coach to my local Freightliner shop and found out the issue. The high pressure oil pump (HEUI) was going bad. This supposedly is something that sometimes happens in the Cat C7 engines. The problem is that when it is going, most of the time it puts metal shavings into the oil and into the injectors, requiring that the injectors be replaced.

The engine only has 40K miles on it when I purchased it at 8 years old, it had only 12K miles on it and I did not have past maintenance history records. That is why I purchased an extended warrantee.

This was an expensive repair - $5600. Thank goodness I purchased an extended warrantee when I purchased the coach and they paid for the repair. The warrantee has more than paid for itself at this point and I have about a year left on it.

So if you are having issues with the engine not responding to the throttle, you should go have it checked out. At some point, it would have failed completely and I would have been stuck on the side of the road.

Thanks for the update, nice when the OP comes back and lets us know the root cause. Good thing you had the warranty.