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Pete
Pete, Automotive Mechanic
Category: Transmissions
Satisfied Customers: 27853
Experience:  GM and Mercedes vehicle technician.17 years experience.
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1998 International 4900 Allison MD3560 Original concern:

Customer Question

1998 International 4900 Allison MD3560 Original concern: transmission would not slip at idle. No codes logged. Applying brakes to come to a complete stop would stall the truck. Truck could be restarted in neutral, but would lurch ahead and attempt to drive
through the brakes after pressing "D". Once in motion, the transmission shifted up and down perfectly. Original solution: Plastic fill cap on transmission had come loose and let dust and gravel into the transmission. Removed pan, changed filters, cleaned control
valves as best as possible with brake clean and compressed air. No metal fillings or clutch material were found in the filters. Changed filters and fluid (transynd) twice. Truck was now able to idle in neutral with foot on the brake, but had shifting issues.
Shifting issue: Reverse seems to engage at the normal time after "R" is pressed. "D" seems to engage at the normal time after button is pressed - ONLY when the fluid is cold and the truck has not moved. Once the transmission has been driven, the vehicle will
actually roll backwards on an incline, in "D" at idle. When the accelerator is pressed, the truck does not move until the rpm's have climbed higher than idle. This "slip and delayed engagement" is more pronounced as the fluid gets warmer. The transmission
shifts up correctly, but rather than hold the engine speed locked to the transmission rpm with the accelerator released, once the accelerator is released while the truck is driving down the road, the rpm's drop until the engine is at a complete idle and will
not down shift. As the vehicle is slowed with the brakes, a code appears and the transmission goes into 4th gear fail safe or 1st gear and holds there. Codes have been: 5633, 5443, 5423, 2216, 2511. Codes cannot be cleared until vehicle is shut off and keyed
back on. Then codes can be cleared and truck will once again drive and shift up correctly. If the manual push button shifter is used, the transmission will shift up and down correctly. The vehicle can be driven in "D" and downshifted through the gears to a
stop, without codes. Once accelerating from stop, there is a significant "lag" before the rpm's climb enough to move the vehicle. Another note: after accelerating to city driving speed in "D" and allowing the rpm's to drop to dead idle - out of "sync" with
the transmission, if you rev the engine back up before a code is generated, you can still manually shift down through the gears. Attempted repairs: Replaced input and output speed sensors, took truck to authorized Allison repair shop. They replaced the tone
wheel, did some diagnostics, and weren't able to come up with a solution.
Submitted: 1 year ago.
Category: Transmissions
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Pete replied 1 year ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

My info is limited on your model here but I see no one else has responded and thought I would see if I can help here.

I would have the transmission valve body tested to see if it is binding/at fault here.I have seen in some cases before in the past where the transmission valve body itself can cause this type of fault here needing replaced.If this has already been checked into/tested and no issues found let me know so we can continue.In some cases a simple transmission flush with a flush machine and the correct fluid can remove any debris from the valve body and correct a fault like this here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Thanks Pete.

Customer: replied 1 year ago.
Hi Pete thanks for your reply but I was able to find an ex-Allison employ who came to look at it and found that the two gaskets on either side of the aluminum plate were reversed. Truck is fixed
Expert:  Pete replied 1 year ago.

Your welcome.Glad to hear it has been resolved and once again I do apologize for the delay.If there is anything else I can help with let me know and feel free to rate my help here if you like.

Thanks Pete