Hi, I’m a Navy Diesel Mechanic used to working on engines the size of my truck and am getting beat up by a power steering problem. The truck is a 03 Sierra Z71 5.3L with 180K miles. First I don’t have the Y91 Option which I believe includes the EVO valve everyone is talking about. It also doesn’t have vacuum assisted steering. The truck steers fine in both directions if you are moving above parking lot speed. If you are moving slow or stopped and turn the wheel from straight to right or right to straight it’s fine. If you turn the wheel from straight to left it’s like there is no power assist at all. You can also hear a loud hissing sound. I lifted the front of the truck so both wheels were off of the ground. With the engine running or off the steering wheel turns freely through the entire range of motion. You can also rotate the steering wheel through the entire range of motion by moving the tires back and forth by hand. There is no binding in the steering system at all. I think it’s either the pump or steering box. Then I think it’s not the pump because the truck turns fine from straight to right or right to straight. The pump does not know which direction you are turning. Also, with the truck in park and the engine at 1000-1500 rpm simulating driving it’s still hard to turn the wheel left. So increasing pump rpm does not help the problem. Only actual truck movement allows movement of the wheel to the left. I’m thinking it’s the steering box. What do you think.
Sorry, on the last line above I think it's in the hydraulic side of the steering box.
February, 24, 2012 AT 7:01 PM
EI06002 - 670 GEAR BOX POWER STEERING PUMP, P/S PERFORMANCE
TECHNICAL SERVICE BULLETIN
Reference Number(s): 05-02-32-008C, Date of Issue: March 28, 2011
Superceded Bulletin(s): 05-02-32-008B, Date of Issue: July 18, 2007
Related Ref Number(s): 05-02-32-008, 05-02-32-008A, 05-02-32-008B, 05-02-32-008C
In rare cases, customers may comment on a lack of steering assist when stopped or during parking lot
type maneuvers. A lack of steering assist could occur if the brakes are applied and turning the
steering wheel with the vehicle stopped or during parking lot type maneuvers. This condition will go
away or greatly improve once vehicle begins to move or is above parking lot speeds. Attempting to
steer a stationary vehicle, with the brakes applied, preventing forward motion will require additional
steering effort. This concern can be aggravated by worn tires, low tire air pressure, low power
steering pump pressures, and tires larger than stock size.
1. Perform the "Power Steering System Test" found in SI. Make any necessary repairs based on
1. FOR 2500 AND 3500 VEHICLES ONLY - If diagnostics did not lead to any repair, this
concern is a normal operating characteristic. No further repairs should be made.
2. FOR 1500 SERIES VEHICLES ONLY - If diagnostics did not lead to any repair, this
concern is a normal operating characteristic.
2. If a 1500 Series vehicle is equipped with a 670 gear box, replacing it with a 680 gear box may
increase the customer satisfaction.
3. To determine if the vehicle is equipped with a 670 gear box, inspect the mounting bolts that
attach the stub shaft housing. A 670 gear box will only have 3 mounting bolts. If the stub shaft
housing does not have any mounting bolts or has 4 bolts - DO NOT PROCEED WITH THIS
Model(s): 2003-2006 Cadillac Escalade, Escalade ESV, Escalade EXT; 2003-2006 Chevrolet
Avalanche, Suburban, Tahoe; 2003-2007 Chevrolet Silverado Classic; 2007-2010
Chevrolet Silverado 2500-3500 Series Only; 2007-2012 Chevrolet Suburban 2500-
3500 Series Only; 2003-2006 GMC Yukon, Yukon Denali, Yukon XL; 2003-2007
GMC Sierra Classic; 2007-2010 GMC Sierra, Yukon XL 2500-3500 Series Only; 2007-2012 GMC Yukon XL 2500-3500 Series Only
Supercedes: This bulletin is being revised to add model years and models. Please discard Corporate
Bulletin Number 05-02-32-008B (Section 02 - Steering).
IMPORTANT: In all cases, it is recommended that the proper tire size and the
maximum tire pressure is set according to the manufacturer's
specification as noted on the door placard; especially for the front
EI06002 - 670 GEAR BOX POWER STEERING PUMP, P/S PERFORMANCE CONCE. Page 1 of 2
BULLETIN. The vehicle is not equipped with a 670 gear box.
4. If replacing a 670 gear box with a 680 gear box, it will be necessary to replace the power
steering gear, union fitting and both inlet O-ring seals.
For vehicles repaired under warranty, choose the one labor operation that reflects the corrective
action: Warranty Information
Part Number Description
88965542 Power Steering Gear
26025709 Union Fitting
26001594 Inlet O-ring Seal
Labor Operation Description Labor Time
E9050 Pump Assembly, Power Steering - Replace
Use Published Labor
E9740 Gear Assembly, Power Steering - Replace
Use Published Labor
EI06002 - 670 GEAR BOX POWER STEERING PUMP, P/S PERFORMANCE CONCE. Page 2 of 2
This is a tech service bulliten, but also check to see if the shaft on the pump broke, try pulling it outward if it moves to much, it probably the pump.
February, 24, 2012 AT 7:52 PM
Merlin, thank you for the reply. I think you helped me a few years ago with a TB question on this truck, which was exactly what you said it was. I have seen this bulliten and was confused by item 2: If a 1500 Series vehicle is equipped with a 670 gear box, replacing it with a 680 gear box may increase the customer satisfaction. My only question is that if I do have the 670 box which I have to check, how would this be an issue after 180K miles. What would make the 670 box work for 180K miles and then require an upgrade to the 680 box. If I do have the 670 box would you recommend replacing it with th e680 before looking at the pump.
February, 24, 2012 AT 8:37 PM
Dirt may be an issue as far as the pressure relief valve clogging up. If you can try purging the old fluid it might help. How are the brakes? Hard pedal or normal? Try this, pump the brakes with the truck off, pump until all assist is gone. Hold pedal down and start the truck, pedal should sink a bit then rebound a bit. It is more important for it to sink(soften). As far as the 670 vs 680, if it turns out to be the box, now is the time to replace with the updated one, I assume you are keeping it?
March, 4, 2012 AT 1:09 AM
Merlin, sorry it took me so long to get back to you. Attached a pic of the steering gear. Are the three bolts, 1 of which i'm pointing to the picture the bolts mentioned in line 3 of the service bulletin above? If so I will replace it with a 680 box GM 88965542? Just trying to make sure i'm getting the right part. GM parts direct says that the 680 gear doesn't go with the VIN for the truck. I'm guessing that it only references original equipment against the VIN. Thanks for teh help.
March, 4, 2012 AT 3:26 AM
Yes there bolts that go through the frame. Use the part number in the tsb
March, 17, 2012 AT 8:45 PM
Merlin, thanks for the advice on this problem. Replaced the box today with the 680 and we are back to normal. One thing though. I used the column lock pin, and everything went back in perfectly as it came out. The steering shaft and pitman arm all lined up perfectly, but now to stay straight while driving the wheel needs to be turned slightly right. If you hold the wheel straight the truck starts veering left. I think that it's because the 680 box is slightly larger than the 670. I'm guessing that it can be fixed with an alignment? What do you think? Thanks for all of the help.
March, 17, 2012 AT 9:44 PM
Alignment, and or other worn front end parts. Tire pressures, or even brake caliper drag.