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Snap Ring Breakage On New Process Output Shaft
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Date: March 1999
Models: 1994-1999 (BR/BE) Ram Truck
Includes all vehicles equipped with a NP/NV 231, 233, 241, 245, and 246 transfer cases.
For more than a decade, we have had breakage problems with the snap ring that is located on the main shaft (output shaft), directly behind shaft rear bearing. The transfer cases that are affected by this problem were manufactured by New Process from 1988 to present and do not have a bolt-on rear yoke. In most cases, a transfer case with a bolt-on rear yoke will not have a snap ring on the main shaft bearing. The problematic transfer cases are found in General Motors and Chrysler full size pickups from 1988 to the present and in some mid-size 4X4 vehicles from 1992 to the present.
Although there are some cases of fatigue breakage, these snap rings usually break as a result of excessive forward force on the output shaft. As the rear suspension moves up and down, the changing geometry of the drive shaft moves the yolk backward and forward. Any spline bind further magnifies the effect of this motion. Aging lubricants and increased torque loads also add to this problem.
Other changes in the vehicle can also contribute to forces on the output shaft (see Fig. 1). Lift kits change the geometry of the drive shafts. Care should be taken so that the U-joint does not exceed 7-1/2 degrees. Increasing tire size also puts more load on the drive line components. In addition, we can't forget the always popular overloading the vehicle.
For years we have lived with customer complaints about pickups that had a clunk or release feeling as the vehicle came to a stop or as they released the brake to go again. The fix was to put a lubricant that contained Teflon on the splines (GM part #12345718). All we were doing was making the splines more slippery, thus reducing some bind, yet it did make the customer happier.
The original snap ring has a hardness of about 60 Rockwell C. This may be too brittle some of the forces to which it is exposed. A better substitute may be the eyelet snap ring (Mopar Part # 06025570), found on the 727 output shaft. It is about .005 " thicker and has a hardness of about 51 Rockwell C (see Figure 2). This snap ring is the correct size for most 241, 245, 246, and 233 transfer cases. For the :231 and other smaller transfer cases, the eyelet snap ring found on the 904 output shaft is the correct diameter but is .015" too thick. It must be surface ground to about .075"-.078" to work. Substituting these alternatives for the more brittle, original snap rings should reduce the likelihood of snap ring breakage.
Awareness of some of the factors that contribute to snap ring breakage can be helpful in understanding this problem and perhaps, preventing it. Hopefully, by utilizing alternative parts, you and your customers will see better results in the long run.
It appears that this Tip was originally published in the March 1999 issue of Transmission Digest.
This page was edited on: May 3, 2004