Owner Notification Letter

Dear GMC Truck Owner:

Product improvements were made on all 1991 Sierras and Suburbans equipped with automatic transmissions to help in maintaining the proper transmission fluid level. Transmission fluid level is very important to transmission life and performance; therefore, GMC Truck will make these improvements on 1988-90 C/K Sierras and R/V Suburbans.

Operating your Sierra or Suburban with an overfilled transmission, pulling loads heavier than the vehicle is equipped to pull, or otherwise overloading the vehicle beyond specifications can result in abnormal pressure build-up in the transmission. If abnormal pressure does build up in the transmission it is possible for transmission fluid to come out the filler tube onto hot engine parts.

The possibility of a transmission fluid fire is remote. However, we wanted our owners to have the benefits of the improvements which address this concern, and the maintenance of a proper transmission fluid level.

These improvements consist of (1) revising the transmission fluid level indicator (dipstick) markings so they can be more easily understood, (2) adding a seal at the fill tube inlet end to help prevent fluid from coming out of the fill tube, and (3) revising the fluid level checking procedure in the owner's manual to provide for a "cold fluid level check. (Note: A "hot" check must follow when fluid is added during a cold check.)

This product improvement applies to BOTH 3-speed automatic transmissions and 4-speed overdrive automatic transmissions.

Because a new dipstick can be installed easily, for your convenience we have included a new dipstick and installation instructions with this letter. However, if you desire, your GMC Truck dealer will install the dipstick for you at no charge.

You will find an owner's manual supplement pertaining to automatic transmission fluid with this letter. Peel the protective tape off the pre-gummed area of the owner's manual supplement and place it in the Automatic Transmission Fluid section of your owner's manual.

Please review the updated information on towing with an overdrive equipped automatic transmission and keep it in your owner's manual.

The enclosed postage paid owner reply card identifies your vehicle. Please complete the card to indicate that the campaign repair has been completed and return the card to us. However, if you have sold or traded your vehicle, please furnish us the complete name and address of the person you sold or traded your vehicle to and return the card to us.

We appreciate your cooperation in this matter. We have taken this action in the interest of your continued satisfaction with our product.