Shift adaptation issues: Potential causes of a 2-3 shift bump

Shift adaptation issues: Potential causes of a 2-3 shift bump

For shift adaptations to perform adequately, all required inputs must be functional. Of course, the solenoids and transmission components must also be functional. The type of inputs required for shift adaptations to function as designed will have some variations based on year, make and model. 

For example, when Chrysler pioneered their 41TE clutch to clutch shifting transmission with no one-way clutch, they used shift solenoids which simultaneously controlled clutch apply. Clutch adaptations were presented via a clutch volume index numbering system. Within this program, they included a unique feature that had to do with the 3-4 shift which required the release of the Underdrive Clutch and the applying of the 2-4 clutch. If this didn’t take place properly, a bind-up could take place. At the vehicle speed with which this could occur, it would be dangerous. So, they wrote a 3-4 shift abort into their adaptation program. 

One aspect of the adaptation program is to watch gear ratio changes via the input and output speed sensors. By doing this, they watch the rate of RPM change of each of these two sensors. If the input RPM runs up too high during the change, it indicates a slip or flared shift. From this data, they would change the rate of apply of the 2-4 clutch and the release of the UD clutch to tighten up the shift. Likewise, if the input RPM dropped during the shift, it would indicate too much of an overlap and cause a harsh shift. It would then adjust clutch apply and release parameters to smooth out the shift. 

The added 3-4 shift abort is when the computer recognizes that a bind-up is occurring and will abort the shift for safety reasons. It identifies this problem by the rate at which the input speed RPM drops. For example, if it sees the input RPM at 2500 and it looks to drop down to 0 as quickly as possible, the computer sees this as a bind-up in the gearbox and aborts the shift before it has a chance to do so. 

From this example, we can clearly see that Input and Output RPM data are necessary inputs in the strategy of shift adaptation. Today, many transmissions utilize shift adaptations. Some even require programming solenoid ID information after replacement or repairs for shift adaptations to function correctly. Others have been using adaptations with their AWD systems. And in doing so, they utilize wheel speed input via the ABS/Traction Control System. When there is a malfunction with this strategy, it too can affect the shifting of a transmission.

Take, for example, a 2012 Dodge Journey AWD equipped with the 62TE transmission that had a complaint of a bump on the 2-3 shift before and after overhaul. After much diagnosing along with countless quick-learn procedures, the shop changed the valve body and the PCM—but the 2-3 shift bump continued. 

Eventually, the shop discovered that the rear tires were larger in circumference than the front tires. The computer perceived this as a slip and would engage the rear electronic differential while the 2-3 shift was taking place causing the bump on the 2-3 shift. Apparently, the circumference difference was not extreme enough to set a C1078 code for “Tire Revolutions Range/Performance,” which would have assisted in the diagnosis of this 2-3 shift problem.


Figure 1.

When the shop did to confirm this to be the cause, the rear differential wire harness connector was disconnected, which resulted in the bump disappearing. The AWD fuse could be removed to accomplish the same test as seen in the wire schematic in Figure 1 (above).

With four new tires with the same circumference installed on the vehicle, the road test that followed confirmed the problem had been eliminated. The 2-3 shift was smooth and occurred without a bump.

This scenario could occur on many vehicles equipped with an active AWD system. One quick and definitive method of diagnosing this condition is to use a stagger gauge which can measure the total circumference of a tire as shown in Figures 2 and 3 (below). It is imperative that all four tires be the same circumference size. This will also prevent shift scheduling and shift feel issues as well.

Figure 2.
Figure 3.

Was this content valuable?

Thanks for your feedback!

You May Also Like

The importance of the follow-up road test after transmission replacement

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer said that “it has a leak, a grinding noise when taking off from a stop, and it just doesn’t seem to shift right.” They went on to tell us that this

RR Tech Feature Oct

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer said that “it has a leak, a grinding noise when taking off from a stop, and it just doesn’t seem to shift right.”

Tips and tricks for Chrysler switch valve plug testing

As technicians, we are often faced with build issues that can sometimes be frustrating at first. But with a little ingenuity, these frustrations can be turned around and made simple. Related Articles – GM 8L90 #7 Check-ball: The overheat that saved the day – ETE Reman: Ever expanding – Shift Pointers: Nissan’s no throttle response

GM 8L90 #7 Check-ball: The overheat that saved the day

Beginning in October of 2015, GM removed the #7 Check-ball from the solenoid valve control body in the 8L90 transmission (see Figure 1). This was done in conjunction with the elimination of the Lube Override Enable Valve from the upper valve body as shown in Figure 2. Related Articles – Jatco/Nissan JF011E critical wear areas

Shift Pointers: Nissan’s no throttle response

Nissan vehicles using continuously variable transmissions (CVTs) are notorious for defaulting to a no throttle response when the vehicle is engaged into gear. There are several malfunctions that can cause this protective failsafe feature to be initiated. A brake switch (stop lamp switch) stuck on, a double-footed driver, blown or incorrect brake bulbs, and wheel

Jatco/Nissan JF011E critical wear areas and vacuum test locations

Sonnax has provided the following guide on critical wear areas and vacuum test locations for the Jatco/Nissan JF011E. Technicians working on these models should find this guide helpful. (Ed. Note: This is an extended version of the guide found in our September issue, with three additional pages). Related Articles – Podcast: Talking CVTs with Transtar,

Other Posts

Clutch Industries launches Clutch System in the U.S.

Australian manufacturer Clutch Industries announced that it is launching two clutch system products for the first time in the United States under the UniClutch brand. Related Articles – Gray Tools releases insulated socket sets – RatioTek introduces new tuner kit for Ram trucks – Sonnax highlights GM 4L heavy-duty input shafts UniClutch (above left) and UniClutch Sport

Tips for success with the GM transmission fast learn process

This article is about failure, something we all experience from time to time. If you are attempting to perform a fast learn process on a GM eight-, nine-, or 10-speed transmission, you may have that temporary feeling of failure, as this process can bring on frustration quickly. Let’s talk about what the fast learn process

Shift pointers: Tricky sensor situations

Sometimes you’re the windshield and sometimes you’re the bug—a phrase many of us have heard and experienced. It’s inevitable. The idea is to be the windshield as much as possible. Shane from Cottman Transmissions had a helluva day but in the end, he was the windshield. Related Articles – CVT maintenance basics – Mercedes-Benz 722.9

Look for the little details: Three transmission repair case studies

Below are three examples of trucks that came into transmission shops, yet either did not have a transmission problem, or had a simpler issue than it originally seemed. Read on for the stories. Related Articles – Infiniti G37 RE7R01A chassis codes set – Honda Accord BB7A six-speed: P2720 code set after collision – Troubleshooting RFE