I know I’ve read where some do but then there’s this:
TO: Chevrolet/GMC Dealers
ATTN: Service Manager and Parts Manager
A new grease, part # 19257121 (in Canada, 19257122), was recently released for lubrication of slip yoke splines to repair a condition of a bump feel or clunk noise at stop or from launch on the vehicles equipped with 4L60 Automatic Transmission (RPO M30) and 2WD. Please see Bulletin # 09-04-17-002C for details.
Do not use the new grease for lubrication of slip yoke splines on 4WD vehicles. The output shaft in a 4WD transfer case does not have a grease retainer to keep the grease from migrating into the transfer case and mixing with the fluid inside. The new grease is not compatible with the Automatic Transmission fluid used in the transfer case and can cause damage if mixed. Lubricate the splines on 4WD vehicles with Automatic Transmission Fluid, P/N 88861003 (in Canada, 88861004). Please refer to Bulletin # 09-04-21-003B for repairing the bump feel or clunk noise condition on 4WD vehicles.
Hmmm…mine is 4WD.