Drivetrain - Excessive Effort When Shift From 2HI to 4HI
TECHNICALBulletin No.: 09-04-19-002B
Date: September 14, 2012
Subject: "4WD System Shift Performance in Cold Ambient Temperatures (Use Synthetic Fluid in Light Duty Front Axles with 8.25 Ring Gears)
Models:
1999-2013 Chevrolet Silverado 1500 Series Models
1999-2013 GMC Sierra 1500 Series Models
Equipped with 4WD and 8.25" Front Axle Ring Gears (Transfer Case RPOs NP2, NQG)
Attention:
It is important to determine the RPO for the transfer case in GWM/IVH prior to applying this bulletin. This bulletin applies ONLY to vehicles equipped with 8.25" front axle ring gears, used in conjunction with a manual transfer case (RPOs NP2, NQG).
Supercede:
This bulletin is being revised to add the 2012-2013 model years and update the Parts Information. Please discard Corporate Bulletin Number 09-04-19-002A (Section 04 - Driveline/Axle).
Condition
Some customers may comment about the effort required to shift from 2HI to 4HI in cold ambient temperatures at -6°C (20°F) or below.
Cause
This condition may be caused by the standard front axle being equipped with conventional mineral oil axle fluid. In cold ambient temperatures, prior to complete warm up, the fluid viscosity is thick. This may affect transfer case shift performance prior to full warm up.
Correction
Drain the front axle fluid and refill with GM SAE 75W-90 Synthetic Axle Fluid, P/N 88900401 (in Canada, 89021678). Refer to Front Axle Lubricant Replacement in SI. It is important to use synthetic fluid in this 8.25" axle to improve the performance of the 4WD system in cold ambient temperatures.
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
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