Yesterday while traveling through the rolling hills of Missouri I noticed that on some hills the usual smooth shift from 6th gear to 5th was quickly followed by a jerking motion as if it really wanted to go into 4th it did not go there. This happened several times in my mile journey.
I have Silverleaf, what parameters should I monitor to gather more pertinent detail. This very problem was very apparent when the cruise was set on my unit. It is older the yours, but with the same problem. It turned out to be a problem with the Alternator voltage regulator s. They put out a noise signature on the 12 volt wiring. Good test-- take a drive and see if the cruise control works when engaged.
If it works fine, drive for a period of time. Disengage the cruise and then reengage it. Do you notice the same issue with the transmission? I run silveleaf and now monitor the 12 volts to see if the voltage remains stable, if it starts to vary and the little green indicator in the voltage window changes from green to yellow or to red, suspect the alternator.
I would also have an issue with the speedometer jumping or varying and the tachometer reading would remain the same. You could look in the photo gallery and look at my pictures and text regarding alternator and ignition issues. Also, pull out your Allison book or look up Allison diagnostic codes and, using the Allison shift pad with igition on, engine off, check for diagnostic codes.
That will tell you if the transmission has sensed a problem. Thanks for the insight I will have the opportunity to pursue your inputs. After about miles the problem was gone altogether. I am about to change the filters. You can post now and register later.
If you have an account, sign in now to post with your account. Paste as plain text instead.Typical problems of an Allison transmission include abnormal shifts, abnormal stall check speeds, slipping of the clutch and abnormal responses. Other problems include the transmission throwing fluid out of the fill tube, excessive engine flares, intermittent noises and the retarder not functioning properly.
Abnormal shifts in an Allison transmission happen during shifting at high and low speeds. At high shifting, this problem may be caused by a malfunctioning governor valve, leaking vacuum hose or broken mechanical actuator cable.
A loose valve spring adjustment or stuck modulator valve causes problems during low and rough shifting. Leaking oil in the converter housing originates from a defective real oil seal, spoiled input charging pump or cracked converter assembly weld. A defective clutch, leaking clutching pistons and transmission fluid leaking past the control valve are the probable causes of the clutch slipping and chattering in only one range.
Low fluid levels, broken seal rings on the front support hub and open lubrication valves cause slipping of the clutch in all forward ranges. If the shift selector linkage is unhooked, it may cause abnormal responses in the transmission. Failure to engage the shift selector at the selector valve also causes unresponsive movement of the selector lever. High transmission fluid levels and a failed vacuum modulator may throw fluid out in an Allison transmission. A loose dipstick, clogged breather, improper dipstick marking and water in the transmission are also probable causes of the problem.
Weak trimmer valves and leaking forward clutch seals may cause excessive engine flares. Lack of air supply, leaking air lines, malfunctioning check valves and a sticking pressure regulator valve are probable causes of a faulty retarder. Home World View. What Causes a Clutch to Burn Out?This short guide is will hopefully help you diagnose simpler Allison Transmission problems. Allison Transmissions have been around for a hundred years and have set the industry standard for durability.
Modern Allison Transmissions come with a limp mode installed. This is a different shift table that allows the transmission to protect itself from catastrophic failure. This limp mode locks the transmission into third gear, and keeps the torque converter from locking up. It also keeps the transmission from going into reverse!
Keep that in mind. The limp mode is often activated by things an excessive of slippage by the transmission. Here are some common conditions that can trigger a limp mode situation. Third gear should pull a load fast enough on the highway, but it can be challenging to get a load moving.
If you are noticing this problem during hotter weather, you may be able to keep it from happening by installing a transmission cooler. Heat issues are the number one killer of this transmission. Do your best to protect the investment. Even just a little bit extra slip put into the tune, and an Allison Transmission can have problems. It should solve the issue for you. It could be a false positive. The best way to do so is to get a code scanner and scan the code to wipe it.
Modern transmissions are computer controlled, but if you are working on your tank they made transmissions for them in WWII or your classic vehicle you may wish to take a look at the vacuum lines. If it feels like it is shifting toward the engine red line you could have it hooked to the wrong port.
GM sent a letter to customers advising them to bring it in and get it replaced. Amazon has a pretty good compatibility chart on their TCM listing if you would like to check it out. Neutral safety backup switch issues are another common Allison Transmission problem on the GM Duramax versions.
It is part number Make sure that you are performing the scheduled maintenance in order to get the most out of your transmission. Most GM automatics come from the factory with non-synthetic fluid. You should make sure that you are using Allison approved fluids and changing them when they recommend. If you do that you may never even have Allison Transmission problems!!!Speedometer erratic, harsh shifting caused by a faulty output speed sensor in the transmission.
In this video I will show you how to troubleshoot and replace the transmission output speed sensor also known as a vehicle speed sensor. Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium.
There is a 14 day free trial. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures.
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Delayed Downshift clunk when stopping - 2006 Allison 6-Speed
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Delayed Downshift clunk when stopping - Allison 6-Speed. Thread starter RayMich Start date Sep 26, RayMich Well-Known Member.
Messages 4, Reaction score 31 Location Mid Michigan. It has never been raced or abused and the only trailer towing it has seen has been a couple of hundred miles towing a 1, lb flat-bottom boat and about miles towing a U-Haul trailer weighing in at around 2, lbs. The dealer had to replace approx. At least that's what I remember seeing on the repair ticket The last time was two years ago and I have not had any leaks since then.
At 4, miles I changed all fluids to Mobil synthetic oils except for the transmission oil.The problem wasn't fully resolved until the summer of I have compiled this document from notes written at various times during that period. I soon discovered that the torque converter lockup clutch wasn't working, so the engine was revving higher than usual and engine rpm was changing with power level rather than road speed.Why is My Transmission Shifting Hard?
We exited in Glenwood Springs to check this out. I also found that the transmission would not shift to neutral or reverse. VMSpc showed the shift showed N when I pushed neutral on the transmission control panel. But the console display still showed "6", and it was indeed still in gear. This transmission state is often called "limp mode" - a built-in protective behavior for some types of Allison transmissions when a serious problem is sensed.
Transmission temperature was normal. I shut the engine off, and then restarted. The warning light went off, and the transmission shifted normally between N, D, and R. But as I accelerated up the ramp back onto the expressway, the rig again lurched as it shifted 3 to 4? We continued driving in limp mode until the next exit. Nothing else appeared to be wrong. VMSpc showed that transmission fluid temperature was about F.
The engine was revving higher, fuel mileage was down, and the engine was running a bit warmer around coolant temp. After exiting, I again shut off the engine and restarted, and the error went away. And again, recurred as I accelerated onto the expressway.
I again drove to the next exit. This time, I shut off and restarted, then accelerated very gently onto the highway, taking a couple of miles to get up to 60 mph. No problem - the transmission worked normally. I engaged the cruise control, accelerated gently to 62 mph and continued without problem. I experimented a bit. At one point, on a downgrade, I let the engine brake engage fairly forcefully. No problem. And on one modest upgrade, the transmission down shifted from 6 to 5 at near full throttle - again no problem.
Later, on the way up a long slope, the transmission started malfunctioning again. We pulled into a view area part way up, and when we pulled out again, with hard acceleration on an upslope, the transmission seemed to shift into neutral briefly during the 3d to 4th gear shift, then went into limp mode - with the engine revving about rpm higher than normal, and the transmission oil temp running about F. It had been nearer Again we exited, then shut down and restarted to reset limp mode.
I checked the transmission fluid level with the keypad it was normal. By accelerating gently, particularly at the shift points, I got up to 62 mph in 6th without triggering the malfunction.Forums New posts Search forums. What's new New posts Latest activity.
Allison Transmission Problems
Allison problems. Thread starter gsw Start date Nov 13, I recently brought a diesel pusher contentinal 3. We went to the lake and the next morning the do not shift light was on and it would not go into gear. Finally was able to hit the drive the same time as the engine started and got it home.
I went out several times and started it and it worked fine then the next time the do not shift came on the display on the push button panel flickered a little.
Allison transmission tips
I took the unit out and had it checked out and was told it was fine but there was a code for a power interuption. Put it back in and it worked great. I went out and drove it around yesterday all was well. Went out this morning and it is dead there is no power to the push buttons not a fliker.
Sometimes in starting the engine I can turn the key but it does nothing. If I do it several times it starts. My senses tell me its a relay or something. Any thoughts or ideas would be appreciated. Make sure they are tight and clean.
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