'Active' Transfer Cases

Up To Standards

Subject: Diagnosing problems with Diagnosis of electronically controlled transfer cases Unit: Electronic ‘Active’ BorgWarner 4405, 4406, 4411, 4416; New Venture 126, 136, 146, 226, 236, 246 Transfer Cases Vehicle Applications: Ford and GM trucks Essential Reading: his is the fourth article in a series approach to a problem, you need to devoted to diagnosis of manual follow each step in order every time. If Rebuilder Ttransmissions and transfer cases. you jump around or skip steps you Shop Owner Electronic “active” transfer cases cause will only wind up wasting time unless Center Manager 70% of the tech calls we receive. you are incredibly lucky. Follow the Diagnostician An active transfer case is an electri- yellow brick road and you will get to cally controlled power divider that has be a wizard. R & R the capability of transferring power to To start, you will need access to the Author: the drive axle that needs it without factory wiring and diagnostic trees Mike Weinberg, any input from the driver. Speed sen- and code charts. Some of these units Rockland Standard Gear sors mounted on the front and rear can throw off almost 100 trouble Contributing Editor output shafts inform the computer of codes. You will need a scan tool that wheel speed for each axle. If the speed can access all the vehicle’s computers. between the axles is not the same, the There will be different sets of codes computer interprets this as wheel slip for each computer, and if you cannot and engages an internal clutch pack to access the transfer-case computer or send power to the other axle. When other electronic control modules you the wheel speeds again correspond, will be lost. A good volt/ohmmeter the clutch will return to minimum (preferably with a scope feature) also duty cycle. is a must. Although this process is simple in The last thing you need is common theory, it becomes very complex be- sense and a strong will to RESIST re- cause of other systems in the vehicle. moving the transfer case from the ve- Antilock brakes, stability control, trac- hicle before performing a complete tion control, transmission controls and diagnostic routine. The vehicle is your engine-management systems are all dyno, and if there are multiple sys- connected to the transfer-case elec- tems outside of the transfer case that tronics, so diagnosis and testing must can affect it, pulling out the transfer cover all these systems. The diagnostic case before you have discovered repair section of the manual on any of where the cause of the problem is these transfer cases can run to more means you will be looking at only the than 100 pages, and there is not effects and collateral damage instead enough space in a year’s magazines to of solving the problem. cover it all. The most-common electronic active transfer cases you will see are the Step 1 BorgWarner 4405, 4406, 4411 and 4416, Measure all four tires and check tire and the New Venture 126, 136, 146, pressures. You will need a tape meas- 226, 236 and 246. This article describes ure or a stagger gauge to measure the a step-by-step approach to shortcut tire circumference on each wheel. the diagnostic process and some quick What the sidewalls say is meaning- paths to checking out the most-com- less; you must make sure all pressures mon problems. As in any diagnostic are the same and each tire circumfer-

1 ence is within ⁄4 inch of the others. ty. If the fluid is burnt, contaminat- check codes again to make sure In the repair manuals GM says that ed with debris or has an evil odor, they are all gone. Now test-drive propshaft speeds must be within accept this as part of your diagno- the vehicle and scan for codes 15 rpm of each other. This trans- sis. The burnt fluid can be either a again to see which if any have re- 1 lates into ⁄16 inch on the tires. The cause of your problem or an effect turned and are hard codes. On Ford manuals say tires must be of external problems causing the some vehicle systems you may within 0.006 inch. My experience is clutch pack to overwork. Again, re- have to take a long-enough road 1 that ⁄4 inch will work in real-world sist all the urges to pull out the test for any adaptive logic in the situations. unit until you know for sure that computers to relearn the vehicle. If you are not going to do this every external system is working Any codes that have returned must before working on a transfer case, correctly. Once you correct all ex- be fixed now. save your time and don’t read fur- ternal inputs to the system, you always have time to repair the unit if ther. You can install 50 new units Step 4 in a vehicle with mismatched tires required. Installing a repaired or and none of them will function cor- reman unit will just cause damage Disconnect the output-shaft- rectly. If the tires do not match up to the new unit and result in a speed sensors and read them di- 1 rectly with a scan tool. They must to the ⁄4-inch spec, get the cus- huge waste of time if all systems tomer involved and make sure he are not good to go. read equally at a given road speed. authorizes the tire replacement. A scope feature on your scan tool or ohmmeter is quite helpful here, Measure the new tires, as you will Step 3 see many that do not match up as you will see speed sensors with brand new. Remember that the Check battery voltage to make signals that appear good on the computer is measuring the shaft sure there is sufficient energy scan tool but will show up as noise speeds of the front and rear output available to run all these comput- under higher speeds. If the speed shafts. A tire-size difference will ers, and scan the vehicle for codes. sensors are good, reconnect them fool the computer into sensing that Make sure that your scan-tool pro- and back-probe the computer ter- a wheel is slipping and will create gram can access all the computers minals on the speed-sensor circuits all kinds of misdirection for you. in the vehicle. You cannot do this if to verify that the wiring has good you can read only engine-manage- integrity and that the signal is ac- ment codes. There will be B codes, tually reaching the computer. Step 2 C codes, P codes and U codes that “Why do this if there are no Check the fluid for correct fill must be reviewed. Once you have codes present?” you may be ask- level and quality. Make sure there written down the codes present, ing. Because many times we find is enough of the correct fluid in the disconnect the negative battery that speed-sensor problems will unit, and observe color and quali- lead for 30 seconds, reconnect, and not set a code, especially if they are

More on Clutch Noise

n his Up to Standards article in November, Mike Weinberg wrote about noise diagnosis and identified the clutch as Ione source of noise that a driver can hear. The clutch disc has damping that is supposed to prevent engine vibration from reaching the transmission, he noted. Bernie Solomons, vice president of Daikin Clutch Corp., says using a replacement clutch disc not designed specifically for the vehicle being serviced can allow vibration to reach the transmission and create noise in the passenger compartment. Exedy, an OEM supplier, tunes clutch discs to each specific car; e.g., the latest Cobalt 2.2- and 2.4-liter, for which the company is the OEM clutch supplier, Solomons said. This disc is a highly sensitive wide-angle-damper type tuned specifically to this car to prevent engine vibrations from being transmitted to the gearbox. Ongoing, there are many other applications requiring specifically designed clutch discs. What happens in the market is that there are many aftermarket suppliers – many huge chain suppliers that supply the average mechanic – whose discs may be made in China and aren’t tuned to avoid transmitted noises, he said. The repackager uses the OEM supplier’s cover with the cheap import disc, which is an old unconventional type that’s not designed to stop NVH (noise, vibration and harshness). As a result, shop customers phone Exedy because its logo is on the cover and they mistak- enly think the entire kit from the chain store came from the company. The aftermarket manufacturer of the disc can’t engineer to the OEM supplier’s standard and copy it because of patent issues, Solomons said.

©2007 Transmission Digest. Reproduced with permission. For subscription information call 800-274-7890 Up To Standards “Antilock brakes, stability control, traction control, transmission controls and engine-management systems are all connected to the transfer-case electronics, so diagnosis and testing must cover all these systems.” sending signals to the computer ness from under driver’s seat to have 4W high or low. Bad front or but the signals do not match each transfer case. Replace harness. rear output-shaft speed sensors or other precisely. You now know 2000-and-up models, bad speed wiring. Will not show a code. Read that the computer is getting the sensors or bad connector at the speed sensors with ohmmeter or correct information. transfer case. Check for corrosion, scope. If sensors match, read signal loose or bent pins; fix or replace as at the control module to check cir- necessary. cuit integrity. Step 5 Bump, bump, bump on hard ac- 236-246 – low or no fluid. Check With all codes removed and any celeration, no codes present – re- rear case for leak at hole worn electronic problems solved or replace transfer-case fluid with through by oil-pump locating tabs. paired, and the transfer case func- Chatter Free, p/n RSG-CF. Replace case. tioning properly, you are finished. 4405-4411 neutralizes on throttle 236-246 – excessive endplay at If you clear the codes and resolve lift; grinding noise; nose leaves on rear output shaft. Rear output- any electronic problems but the acceleration – replace transfer-case shaft bearing has worn out bearing transfer case does not work prop- assembly with unit that has cor- bore. Replace case. erly, we now know we are dealing rected internal geometry to pre- 236-246 – Do not use aftermar- with a mechanical problem. Now vent side loading of shift fork and ket actuator motors that use bush- review the complaint. Does the rail. ing in case; same as 136-146 transfer case chatter on turns? 4405-4411 in normal driving previously mentioned. Disconnect the transfer-case har- produces banging noise that ness and drive again. Does it still sounds like a broken spider gear – Note: In 1998-2002 236-246 chatter? Check for a bad rear or same as above: Replace transfer- transfer cases, the front driveshaft bad posi differential, or on Ford case assembly with corrected is always engaged, and the clutch units determine whether the unit is model. pack has 100 pounds of preload. In locked in failsafe mode. If the chat- later models the front driveshaft ter is gone, you have an electronic will turn by hand with slight re- problem such as a failed transfer- New Venture Gear sistance. case control module that will 126-226 – binding on turns. throw no codes. Replace fluid with Chatter Free, Everyone looks for the “quick p/n RSG-CF. Enter diagnostic rou- fix,” but in the real world there are Common problems with the tine and observe clutch-pack appli- no shortcuts. Working from the BorgWarner 4405, 4406, 4411 and cation rates and percentage of duty factory schematics and diagnostic 4416 transfer cases in Ford vehi- cycle. If front thrust bearing has trees will help you solve the elec- cles: failed, clutch will over-travel, al- trical issues. Knowing how the No response to scan tool on 2002 lowing encoder motor to go out of unit works and is related to other Ford Explorers – failed 4WD con- range. vehicle systems will keep you from trol module 136-146 – binding on turns. chasing your tail. The routine we Erratic rear output-shaft speed- Replace fluid with Chatter Free, listed here will help you to have a sensor reading with new speed p/n RSG-CF. Do not use aftermar- consistent outcome every time sensor, 1996-2004 Ford models – ket actuator motors that use a without wasted effort. The tips transfer-case rear output-shaft bushing in the case for the apply mentioned are problems that show bearing has worn out the bore in shaft. The OE unit uses a needle up on the tech line constantly. I the case, allowing too much end- bearing in the case for the apply wish all of you a happy holiday play. Replace the rear transfer-case shaft. The clutch has a 300-pound season and a healthy, prosperous half. application force and will lock the New Year. TD Binding on tight turns at low aftermarket motor into the bush- speed, such as on a parking lot, ing, causing permanent clutch en- 1995-99 Explorers – bad speed sen- gagement. sors, or shorted or open short har- 236-246 – no auto 4WD; will