8 GEARS March 2010

Do You Have a Nagging TCC Shudder?

In this issue of Keep Those Trannys Rolling, we’re going to look at a 2006 Jeep Grand Cherokee with a

nagging TCC shudder. Our story begins with a call to the

ATRA Technical HotLine from Devon Long. Devon, a technician from Dales A-1 Transmission in Mitchell, South Dakota, was dealing with a nagging TCC shudder on a 2006 Jeep Grand Cherokee (figure 1) equipped with a 3.7L engine and a 722.6 transmission (also known as a NAG1). He said it had a nagging TCC shudder that would start at about 30 MPH and would continue up to 75 MPH.

He connected his scan tool and found code P0710 (trans temp) in mem-ory, but there were no current codes in the system. After clearing the transmis-sion temperature code, he went for a test drive and monitored TCC opera-tion.

The Test DriveDuring the test drive Devon moni-

tored TCC duty cycle, TCC desired slip and TCC actual slip while his assistant drove the Jeep. The TCC was being commanded on at about 30 MPH and the TCC duty cycle would climb to around 50%. He could feel the vehicle start to shudder as soon as TCC was commanded on.

The TCC actual slip was all over the place, with anywhere from 0 RPM to over 80 RPM slip while the TCC was shuddering. This indicated that the TCC was actually causing the shudder.

TCC Shudder ConfirmedWith the confirmation of a TCC

shudder, it was time to remove the transmission and inspect the torque converter and TCC apply system.

Keep Those Trannys rolling

by Pete Huscherwww.atra.com

Do You Have a Nagging TCC Shudder?

Figure 1: 2006 Jeep Grand Cherokee with a shudder

10 GEARS March 2010

Do You Have a Nagging TCC Shudder?

With the transmission and torque con-verter on the bench, Devon inspected the torque converter for signs of over-heating; there were none. The torque converter looked okay, but the trans-mission fluid had a weird, slimy feel to it.

With no signs of a torque converter problem, he knew it was time to call the ATRA Technical HotLine for help.

The Call to ATRADevon spoke with ATRA’s lead

technical advisor, Randall Schroeder. Randall explained that, with the TCC duty cycle at around 50%, the TCC desired slip should have been modulat-ing between 40-80 RPM and the TCC actual slip should have been within 10% of that. In this case, TCC actual slip was erratic and excessive.

Randall went over possible causes for the TCC shudder, including prob-lems with the computer control, TCC solenoid, TCC apply circuit, stator, torque converter, and even fluid con-tamination.

As soon as Randall mentioned fluid contamination, Devon mentioned the “weird, slimy feel” he’d noticed. Randall then explained the many prob-lems Chrysler had with moisture enter-ing the transmission system, possibly from the cooler or an external source.

Fluid Contamination Confirmed

To check for fluid contamination, Devon took a sample of the transmis-sion fluid, placed it in a metal container, and heated it on a hotplate (figure 2). As the fluid heated up, he could see small air bubbles forming and steam coming from the surface of the trans-mission fluid, which confirmed the presence of water.

From there the search was on to locate the source of the contamination.

Devon knew he had to inspect the transmission cooling system and radia-tor. He traced the transmission cooler lines to the front of the vehicle, where he found that the transmission cooler lines didn’t go to the radiator: These cooler lines went past the radiator and were attached to a cooling condenser in front of the radiator.

The cooling condenser was a com-bination A/C condenser and transmis-sion fluid cooler. With the transmis-sion cooling system sharing the same condenser as the A/C system, there was a possibility that the A/C system was leaking into the transmission side of the combination condenser and contami-nating the transmission fluid.

But the A/C system appeared to be operating normally and was blowing ice cold, so he concluded that the A/C system wasn’t leaking, or the A/C sys-tem would have been low on refrigerant and been blowing warm.

With the transmission cooler out of the picture, the only remaining source for water contamination was external.

Figure 3: After confirming that the Jeep he was working on wasn’t covered under Chrysler’s recall, Devon replaced the dipstick tube seal (part # 05189087AA

Figure 2: To check for fluid contamination, Devon took a sample of the transmission fluid, placed it in a metal container, and heated it on a hotplate

12 GEARS March 2010

Do You Have a Nagging TCC Shudder?

Source of Contamination Confirmed

While inspecting the transmission case, Devon noticed moisture around the transmission dipstick tube seal. After further inspection, it was obvi-ous that moisture was seeping into the transmission through the dipstick tube seal, possibly from rainwater runoff or A/C system condensation, and con-taminating the transmission fluid. After confirming that the dipstick seal was leaking, he performed an online search and found a Chrysler recall for this exact condition on the 1995 Jeep Grand Cherokee, but the recall didn’t include 1996 models.

According to the Chrysler recall (safety recall #E13), about 100,000 vehicles were affected by this problem. Chrysler recommends pressurizing the transmission case with 2 PSI of air pressure and inspecting the dipstick tube seal for leaks. The recall required replacing the dipstick tube seal whether it was leaking or not.

Chrysler went on to recommend replacing the torque converter if TCC had developed a shudder, and installing a special shield to deflect water from

the dipstick tube seal.After replacing the transmission

dipstick tube seal, installing the water deflection shield, and replacing the torque converter (if needed), Chrysler recommended flushing the entire transmission system with new fluid and resetting the learned adapts in the TCM.

After confirming that the Jeep he was working on wasn’t covered under Chrysler’s recall, Devon replaced the dipstick tube seal (part # 05189087AA; figure 3) and torque converter, rein-stalled the transmission, and flushed the entire system.

He wasn’t able to reset the learned adapts in the TCM with his scan tool, so he sent the vehicle to the local Chrysler dealership to have the TCM reprogrammed with the latest update and reset the learned adapts.

Repair ConfirmedAfter the TCM was reprogrammed

the learned adapts reset, he returned to his shop to recheck TCC operation. With his assistant driving the vehicle, he monitored the TCC duty cycle, TCC desired slip, and TCC actual slip. The

TCC desired slip modulated between 40-80 RPM; the TCC actual slip fol-lowed the TCC desired slip within 2-3 RPM.

The TCC shudder was gone. All indications were that the TCC system was operating properly. He delivered the vehicle; the customer has been driv-ing it for a couple weeks now and says everything seems to be okay.

In ClosingI’d like to thank the crew at Dales

A-1 Transmission (figure 4) in Mitchell, South Dakota, for sharing their story of a nagging TCC shudder with ATRA. If you have a story of an unusual problem and have a successful repair for it, we invite you to share your experiences with ATRA.

Story ideas with successful repairs should be submitted to ATRA Technical Director Lance Wiggins at lwiggins@atra.com. Remember, with your help, every ATRA Member can Keep Those Trannys Rolling.

Figure 4: The crew at Dale’s A-1 Transmissions, South Dakota, Left to Right , Devon, Dale, Daren & Dustin.

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