Available Top Speed Changes – 2019-2020 Chevrolet Silverado 4500HD/5500HD/6500HD

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Service Bulletin Bulletin No.: 20-NA-116
Date: June, 2020
INFORMATION
Subject: Available Top Speed Changes
Brand: Model:
Model Year: VIN: Engine: Transmission:
from to from to
Chevrolet Silverado 4500HD/
5500HD/6500HD 2019 2020 All All
Involved Region or Country North America
Condition Some customers may comment on wanting to change the current top speed on the
vehicle.
Cause Based on how the vehicle was ordered, the truck comes with a standard top speed.
Correction The standard top speed can be changed 2 ways outlined below.
Note: Any changes made to the Maximum Standard
(as built) Speed will be the responsibility of the
customer.
Option 1
Rear
Axle
Ratio
Standard Max
Geared Road
Speed
Optional
Geared
Road Speed
RPO
“Govenor
Up” Speed
4.1
(RPO
066)
79 79 N/A
4.3
(RPO
092)
75 79** 9D6
4.56
(RPO
005)
70 75* 9D7
4.88
(RPO
008)
65 70* 9B9
* — All 141″ WB vehicles (FQT) will be limited to 65 MPH at
4.88, 70 MPH @4.56 & 75 MPH@ 4.30 RAR.
** — All 141″ WB vehicles (FQT) will be limited to 65 MPH
at 4.88, 70 MPH@ 4.56 & 75 MPH@ 4.30 RAR. 4X4 reg
cab (165″ WB – ED9) will be limited to a top speed of 75
MPH. 4X4 crew cab (175″ WB – FNV) will be limited to a top
speed of 75 MPH.
First option (See chart above) is to add calibration for
the appropriate RPO. This will allow a 5 MPH increase
with no hardware.
Page 2 June, 2020 Bulletin No.: 20-NA-116
Option 2
Possible Rear Axle Changes
Change From Change To
4.88 4.10
4.88 4.30
4.88 4.56
4.56 4.10
4.56 4.30
Note: There may be other concerns where a customer/
dealer may want to change from a lower (numerical)
RAR to a higher RAR to improve towing performance.
Possible Rear Axle Changes
Change From Change To
4.10 4.56
4.10 4.88
4.30 4.56
4.30 4.88
4.56 4.88
Note: This is only for 4×2 trucks (4×4 is only 4.30
all the time).
Second option (See chart above), changing gears for
rear axle ratio and calibration will allow a top speed
change greater than 5 MPH. Contact Techline for
Calibrations.
Version 1
Modified Released June 01, 2020
GM bulletins are intended for use by professional technicians, NOT a “do-it-yourselfer”. They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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