With all the technological upgrades to modern transmissions, it may be best to leave the repairs in the hands of professionals. It is easy to get confused as to what needs to be done especially when the code reader does not show any legitimate codes.
Some of the more common problems include but are not limited to the following issues- abnormal shifts, abnormal stall check speeds, slipping of the clutch, and abnormal responses. Sometimes, the transmission may not be installed correctly.
To learn more about these issues and how to fix them, just continue to read our article. It explores the topic to provide you with the most up-to-date information possible. Take a few minutes to see how this information can help you.
This transmission seems to have come with a variety of problems. Not everyone will encounter all of these issues but enough people will. While we provide possible repair solutions it is best to have an experienced Allison transmission technician diagnose the correct problem and provide the appropriate fix.
1. Transmission not installed correctly- if you experience this issue, the good news is that there is nothing wrong with the transmission. The problem lies in how it was installed in your vehicle.
The main source of this problem would be the vacuum lines. There are other parts involved as well and if the lines and those other parts are not connected correctly, then simply reconnect them to the right sports.
2. TCM or transmission control module- it seems that the early versions of this device were defective in most cases. There was a recall issued years ago and if you missed it you may still have a bad TCM monitoring your transmission.
The only repair for this problem would be to replace the TCM. You should contact Allison first to see how the replacement process is done. We cannot say that the recall is still in effect and that you won’t pay any money for the repair. That is between you and Allison.
3. Slipping of the clutch- there are three main sources for this problem. Your clutch may be defective which would account for some of the trouble you have shifting gears.
Or the clutch pistons are leaking and one final source would be if the transmission fluid is leaking past the control valve. The repair for all three would be to replace the defective parts.
This replacement could be something simple as the seals or springs, etc., or you may have to replace the clutch, pistons, and control valve.
4. Abnormal responses- this problem could be found in the shift selector linkage. If it is unhooked, then you will have some problems getting into or out of gear.
Or there may be a problem with the selector valve causing the shift selector to not work correctly. The repair for these problems would be to hook the shift selector back into its proper position and replace any damaged parts in the selector valve.
Other common issues will be too much transmission fluid in the transmission. This will cause some blow by especially if the vacuum modulator. Or there is a loose dipstick, clogged breather, improper dipstick marking, and water in the transmission.
Then there could be a problem with your air supply, leaking air lines and malfunctioning check valves, as well as a sticky pressure regulator, which could be caused by a faulty retarder.
When you experience abnormal shifting, it may take place at both high and low speeds or one or the other. In other words, you may not escape this problem even if you slow down and take your time getting to your destination.
When you face this problem at high speeds, the sources could be one of the following- malfunctioning governor valve, leaking vacuum hose, or broken mechanical actuator cable.
The repairs for these problems are fairly self-evident. Seal up any leaks you find, repair the governor valve, or replace the mechanical actuator cable. These repairs may be above your skill set to do so take your vehicle to the nearest approved Allison transmission specialist.
The same words can apply to abnormal shifting at low speeds. The sources for this problem, when you are not going that fast, are- loose valve spring adjustment, stuck modulator valve, leaking oil, defective real oil seal, spoiled input charging pump, or cracked converter assembly weld.
To diagnose these issues, you may need special equipment and a lot of experience working on transmissions. Finding the right parts may be a bit difficult especially if you are stuck in more rural areas of the country.
If you want some troubleshooting advice and tips, read our article Allison Transmission shift selector problems.
The following was taken from this link. It is a post that lists some of the possible fault codes and their explanations. You may see these if you hook up a code reader. We will just list the codes and their definitions. The explanations are quite lengthy so you will have to go to that link to read them.
2511- Output speed sensor, detected 0 output rpm 1st gear
3233- C3 pressure switch open, 3rd range
5412- oncoming ratio test (after the shift) 1 to 2
5432- oncoming ratio test (after the shift) 2 to 3
5445- oncoming ratio test (after the shift) 4 to 5
5587- oncoming C3PS test (after shift) N1 to R
5611- Range verification test, 1st N1 to R
5622- Range verification test, 2nd
5655- Range verification test, 5th
You may see other codes as well. This is why you will need the help of an experienced Allison transmission repairman. Some of these codes demand a lot of work and may be difficult to find the faulty parts. Plus, they may need specially designed tools to remove and install them.
The following signs may apply to all transmission models and brands and are not limited to just the Allison 3000 or other Allison models.
1. Strange noises coming from the engine or transmission- this happens often and you may hear humming, grinding, whining, and buzzing. The repair will depend on what is wrong.
2. CEL or MIL lights lighting up or blinking- these lights do illuminate when something is wrong with your transmission. Just do not ignore it or wait too long to address the problem.
3. Grinding noise- the gear wheel speed is not synced with the engine and that causes the grinding noise as you fight to get into the next gear. Lots of sources for this noise
4. Leaking transmission fluid- there could be a problem with a seal or gasket. Or worse, there may be a crack in the body of the transmission. Either way, you will need to do some heavy transmission repairs.
5. Unresponsive gear shifting- this was discussed earlier and there could be several parts that have failed or are going bad that create this problem. The shifting may feel sluggish or sticky when they do.
6. Burning odor- transmission fluid can burn and you will know it by the smell. When you smell this odor, you know you need to do some repair work on the transmission.
7. Transmission is noisy in neutral- neutral is supposed to be the ‘safe place’ for transmission but when it starts making noises when in this gear, your transmission is going bad.
8. Slipping gears- this is not always the fault of a lack of transmission fluid. It is a good sign that your transmission is failing and needs to be worked on.
9. Dragging clutch- whenever you experience a problem with a part related to the transmission, it is one sign that your transmission is wearing out. But not always a sign of that problem.
10. Won’t go into gears- this could be a damaged clutch plate or a faulty transmission. Either way, you will need to do some expensive repair work when you experience this problem.
The first place to go would be this link. It takes you to the Allison Transmission Hub web page which has an encyclopedia of knowledge for the Allison transmissions.
This seems t be a subscription-based aid to troubleshooting your Allison transmission. Check it out as it does have a free membership plan. Unfortunately, the free plan brings just basic information to your problem.
Then if you do not like that option, you can go to our go-to website for manuals. Manual Lib has an Allison Transmission 3000 Mechanic's Tips manual. It is 83 pages long and contains lots of help on those pages.
You can download it at this link. Do not be surprised if the download is not free. The last page of the manual has customer service information and contact information that should help you out if you get stuck.
Finally, there is this website. It contains troubleshooting manuals for the 3000 and 4000 transmission models. There are also service and owner’s manuals at that site as well.
If you do not want to download the manual, you can view it by scrolling down to the page or pages you need to read. These links are not the only ones to top resources.
They are designed to get you on the right path to getting the repair information you need. A simple internet search should bring in more top results.
According to one website, the Allison 3000 transmission is rated for mid-duty trucks and vehicles. This is what that website had to say about this transmission:
“Allison Series 3000 units were created for mid-duty trucks and can be adjusted to operate with high effectiveness even under severe conditions. These solutions are equipped with a sophisticated ECU that ensures improved control and diagnostic capacities, and, optionally, a built-in retarder.
These gearboxes have up to 7 gears, including overdrive, and are also equipped with an engine-operated PTO mechanism. These gearboxes are developed to make medium tonnage vehicles more effective and easy to operate.” (source)
This link takes you to an Allison web page that talks about their 3000 and 4000 transmissions and what they can do for you. One piece of important information is found lower down on that web page and reads:
“Calibrated to the vehicle’s particular operating requirements, Allison prognostics monitor various operating parameters to determine and alert when service is due.” (bold ours).
Part of your shifting issues may be found in the shift solenoid. Your code reader may illuminate up to 24 different P fault codes if this is the problem. The location of the solenoid is in the valve body and it is not a cheap repair.
The repair can cost between $100 to $350 with the pack costing between $450 and $700. While you can drive with a faulty shift solenoid, it is not recommended you do so. More damage to your transmission can be done if you do. Here are the signs of a faulty shift solenoid:
1. Check engine light illuminates
2. The transmission warning light illuminates
3. Shift delays
4. Skipping gears
5. Stuck in gear
6. Hard to down or up shift
7. Your vehicle goes into limp mode
The Allison 3000 transmission is still a very solid and reliable device to have in your vehicle. Despite all of the above problems, it can last for a very long time if you take care of it.
Proper maintenance goes a long way toward avoiding some of the above issues just discussed. When you encounter a problem, do not delay in getting your vehicle to the shop. Any delay may cause more damage and increase your repair bill substantially.
Talk care of your transmission so it does not fail at the wrong moment in the wrong place.