Skip to Product Info
    • B&M B&M Shift Improver Kit - GM TH400/475 Transmissions 20261
    • B&M B&M Shift Improver Kit - GM TH400/475 Transmissions 20261
    • BMM20261.jpg
    • 20261.jpg
    • 20261_2.jpg
    • 20261.jpg
    • 20261_2.jpg
    Sale!

    B&M B&M Shift Improver Kit - GM TH400/475 Transmissions 20261

    Vendor: B&M
    Part Number: 20261
    Save $11.50
    Sale Price $87.45 Regular Price $98.95

    Available to order. In-stock orders typically ship in 1 to 2 business days.

    Not sure it fits your vehicle?
    Email sales@berryperformancesales.com with your year, make, model and engine, and we'll help you check fitment before you order.
    Fast Fulfillment: In-stock orders typically ship within 1 to 2 business days.
    Free Shipping on Orders Over $99 | Excludes freight shipments
    International Shipping Available: email sales@berryperformancesales.com for a quote.
    Payment & Security

    Secure, encrypted checkout. Card details go straight to the payment processor and are never stored by us.

    • Amazon
    • Amazon
    • American Express
    • Apple Pay
    • Diners Club
    • Discover
    • Google Pay
    • Mastercard
    • PayPal
    • Shop Pay
    • Venmo
    • Visa
    Share to:
    The B&M® Shift Improver kits™ feature two options to recalibrating your 1988-1994 GM TH400 and TH475 automatic transmissions. First is the HEAVY DUTY set-up, giving you firm positive shifts without loss of driver comfort for improved performance in all street vehicles. This is a great option for performance street driving or towing. The second is our STREET/STRIP set-up. Be warned, this will deliver firm positive shifts you will feel, along with easily chirping the tires when shifting somewhat aggressively. This setting is recommend for high performance street/strip use, or for competitive events when you want the hardest, quickest shifts possible from a shift improver kit.


    B&M B&M Shift Improver Kit - GM TH400/475 Transmissions 20261


    Specifications:

    Automotive Item Grade High Performance
    Brand B&M
    California Proposition 65 Chemical Name Cadmium and cadmium compounds
    California Proposition 65 Required Yes
    Category Transmission
    Emission Code 5
    Gasket Included Yes
    Instructions Included Yes
    part type Automatic Transmission Shift Kit
    Product Type Automatic Transmission Valve Body Kit
    Sub Category Service Kits
    Warning California Proposition 65
    Automotive Item Grade High Performance
    Brand B&M
    California Proposition 65 Chemical Name Cadmium and cadmium compounds
    California Proposition 65 Required Yes
    Category Transmission
    Emission Code 5
    Gasket Included Yes
    Instructions Included Yes
    part type Automatic Transmission Shift Kit
    Product Type Automatic Transmission Valve Body Kit
    Sub Category Service Kits
    Warning California Proposition 65
    Description_INV SHIFT IMPROVER KIT 88-94 TH400
    Description_ASC Fits 1988-1994 Chevrolet, Buick, Olds, Pontiac, GMC TH400 Automatic Transmissions.
    Description_DES B&M Shift Improver Kit - GM TH400/475 Transmissions
    Description_EXT 1988-1994 GM TH400/475 Automatic Transmissions.
    Description_MKT The B&M® Shift Improver kits™ feature two options to recalibrating your 1988-1994 GM TH400 and TH475 automatic transmissions. First is the HEAVY DUTY set-up, giving you firm positive shifts without loss of driver comfort for improved performance in all street vehicles. This is a great option for performance street driving or towing. The second is our STREET/STRIP set-up. Be warned, this will deliver firm positive shifts you will feel, along with easily chirping the tires when shifting somewhat aggressively. This setting is recommend for high performance street/strip use, or for competitive events when you want the hardest, quickest shifts possible from a shift improver kit.
    Description_FAB Perfect for Off-Road, Towing or Street/Strip Use
    Description_FAB Eliminates Soft and Sluggish Shifts
    Description_FAB Over 65 Years of B&M Quality
    Description_FAB Eliminates Shift Overlap
    Description_FAB Provides Crisp Shifts
    Description_FAB Easy Installation
    Description_INV SHIFT IMPROVER KIT 88-94 TH400
    Description_ASC Fits 1988-1994 Chevrolet, Buick, Olds, Pontiac, GMC TH400 Automatic Transmissions.
    Description_DES B&M Shift Improver Kit - GM TH400/475 Transmissions
    Description_EXT 1988-1994 GM TH400/475 Automatic Transmissions.
    Description_MKT The B&M® Shift Improver kits™ feature two options to recalibrating your 1988-1994 GM TH400 and TH475 automatic transmissions. First is the HEAVY DUTY set-up, giving you firm positive shifts without loss of driver comfort for improved performance in all street vehicles. This is a great option for performance street driving or towing. The second is our STREET/STRIP set-up. Be warned, this will deliver firm positive shifts you will feel, along with easily chirping the tires when shifting somewhat aggressively. This setting is recommend for high performance street/strip use, or for competitive events when you want the hardest, quickest shifts possible from a shift improver kit.
    Description_FAB Perfect for Off-Road, Towing or Street/Strip Use
    Description_FAB Eliminates Soft and Sluggish Shifts
    Description_FAB Over 65 Years of B&M Quality
    Description_FAB Eliminates Shift Overlap
    Description_FAB Provides Crisp Shifts
    Description_FAB Easy Installation


    This Part Fits:

    Year Make Model Submodel Notes
    1988 Cadillac Brougham Base
    1989 Cadillac Brougham Base
    1990 Cadillac Brougham Base
    1988 Cadillac Brougham d'Elegance
    1989 Cadillac Brougham d'Elegance
    1990 Cadillac Brougham d'Elegance
    1989 Chevrolet Blazer Scottsdale
    1990 Chevrolet Blazer Scottsdale
    1989 Chevrolet Blazer Silverado
    1990 Chevrolet Blazer Silverado
    1989 Chevrolet C1500 Cheyenne
    1990 Chevrolet C1500 Cheyenne
    1989 Chevrolet C1500 Scottsdale
    1990 Chevrolet C1500 Scottsdale
    1989 Chevrolet C1500 Silverado
    1990 Chevrolet C1500 Silverado
    1990 Chevrolet C1500 WT
    1989 Chevrolet C2500 Base
    1990 Chevrolet C2500 Base
    1989 Chevrolet C2500 Cheyenne
    1990 Chevrolet C2500 Cheyenne
    1989 Chevrolet C2500 Scottsdale
    1990 Chevrolet C2500 Scottsdale
    1989 Chevrolet C2500 Silverado
    1990 Chevrolet C2500 Silverado
    1989 Chevrolet C3500 Cheyenne
    1990 Chevrolet C3500 Cheyenne
    1989 Chevrolet C3500 Scottsdale
    1990 Chevrolet C3500 Scottsdale
    1989 Chevrolet C3500 Silverado
    1990 Chevrolet C3500 Silverado
    1989 Chevrolet G10 Sportvan
    1990 Chevrolet G10 Sportvan
    1989 Chevrolet G20 Beauville
    1990 Chevrolet G20 Beauville
    1989 Chevrolet G20 Chevy Van
    1990 Chevrolet G20 Chevy Van
    1989 Chevrolet G20 Sportvan
    1990 Chevrolet G20 Sportvan
    1989 Chevrolet G30 Beauville
    1990 Chevrolet G30 Beauville
    1989 Chevrolet G30 Chevy Van
    1990 Chevrolet G30 Chevy Van
    1989 Chevrolet G30 Hi-Cube
    1990 Chevrolet G30 Hi-Cube
    1989 Chevrolet G30 Sportvan
    1990 Chevrolet G30 Sportvan
    1989 Chevrolet K1500 Cheyenne
    1990 Chevrolet K1500 Cheyenne
    1989 Chevrolet K1500 Scottsdale
    1990 Chevrolet K1500 Scottsdale
    1989 Chevrolet K1500 Silverado
    1990 Chevrolet K1500 Silverado
    1990 Chevrolet K1500 WT
    1989 Chevrolet K2500 Cheyenne
    1990 Chevrolet K2500 Cheyenne
    1989 Chevrolet K2500 Scottsdale
    1990 Chevrolet K2500 Scottsdale
    1989 Chevrolet K2500 Silverado
    1990 Chevrolet K2500 Silverado
    1989 Chevrolet K3500 Cheyenne
    1990 Chevrolet K3500 Cheyenne
    1989 Chevrolet K3500 Scottsdale
    1990 Chevrolet K3500 Scottsdale
    1989 Chevrolet K3500 Silverado
    1990 Chevrolet K3500 Silverado
    1990 Chevrolet R1500 Suburban Scottsdale
    1990 Chevrolet R1500 Suburban Silverado
    1989 Chevrolet R2500 Silverado
    1989 Chevrolet R2500 Suburban Scottsdale
    1990 Chevrolet R2500 Suburban Scottsdale
    1989 Chevrolet R2500 Suburban Silverado
    1990 Chevrolet R2500 Suburban Silverado
    1989 Chevrolet R3500 Cheyenne
    1990 Chevrolet R3500 Cheyenne
    1989 Chevrolet R3500 Scottsdale
    1990 Chevrolet R3500 Scottsdale
    1989 Chevrolet R3500 Silverado
    1990 Chevrolet R3500 Silverado
    1990 Chevrolet V1500 Suburban Scottsdale
    1990 Chevrolet V1500 Suburban Silverado
    1989 Chevrolet V2500 Suburban Scottsdale
    1990 Chevrolet V2500 Suburban Scottsdale
    1989 Chevrolet V2500 Suburban Silverado
    1990 Chevrolet V2500 Suburban Silverado
    1989 Chevrolet V3500 Cheyenne
    1990 Chevrolet V3500 Cheyenne
    1989 Chevrolet V3500 Scottsdale
    1990 Chevrolet V3500 Scottsdale
    1989 Chevrolet V3500 Silverado
    1990 Chevrolet V3500 Silverado
    1988 GMC C1500 Sierra
    1989 GMC C1500 Sierra
    1990 GMC C1500 Sierra
    1988 GMC C1500 Sierra SLE
    1989 GMC C1500 Sierra SLE
    1990 GMC C1500 Sierra SLE
    1988 GMC C1500 Sierra SLX
    1989 GMC C1500 Sierra SLX
    1990 GMC C1500 Sierra SLX
    1988 GMC C2500 Sierra
    1989 GMC C2500 Sierra
    1990 GMC C2500 Sierra
    1988 GMC C2500 Sierra SLE
    1989 GMC C2500 Sierra SLE
    1990 GMC C2500 Sierra SLE
    1988 GMC C2500 Sierra SLX
    1989 GMC C2500 Sierra SLX
    1990 GMC C2500 Sierra SLX
    1988 GMC C3500 Sierra
    1989 GMC C3500 Sierra
    1990 GMC C3500 Sierra
    1988 GMC C3500 Sierra SLE
    1989 GMC C3500 Sierra SLE
    1990 GMC C3500 Sierra SLE
    1988 GMC C3500 Sierra SLX
    1989 GMC C3500 Sierra SLX
    1990 GMC C3500 Sierra SLX
    1988 GMC G1500 Rally
    1989 GMC G1500 Rally
    1990 GMC G1500 Rally
    1988 GMC G1500 Rally STX
    1989 GMC G1500 Rally STX
    1990 GMC G1500 Rally STX
    1988 GMC G2500 Rally
    1989 GMC G2500 Rally
    1990 GMC G2500 Rally
    1988 GMC G2500 Rally STX
    1989 GMC G2500 Rally STX
    1990 GMC G2500 Rally STX
    1988 GMC G2500 Vandura
    1989 GMC G2500 Vandura
    1990 GMC G2500 Vandura
    1988 GMC G3500 Magnavan
    1989 GMC G3500 Magnavan
    1990 GMC G3500 Magnavan
    1988 GMC G3500 Rally
    1989 GMC G3500 Rally
    1990 GMC G3500 Rally
    1988 GMC G3500 Rally Camper Special
    1989 GMC G3500 Rally Camper Special
    1990 GMC G3500 Rally Camper Special
    1988 GMC G3500 Rally Custom
    1988 GMC G3500 Rally STX
    1989 GMC G3500 Rally STX
    1990 GMC G3500 Rally STX
    1988 GMC G3500 Vandura
    1989 GMC G3500 Vandura
    1990 GMC G3500 Vandura
    1988 GMC G3500 Vandura Special
    1989 GMC G3500 Vandura Special
    1990 GMC G3500 Vandura Special
    1988 GMC Jimmy Base
    1989 GMC Jimmy Base
    1990 GMC Jimmy Base
    1988 GMC Jimmy Sierra Classic
    1989 GMC Jimmy Sierra Classic
    1990 GMC Jimmy Sierra Classic
    1988 GMC K1500 Sierra
    1989 GMC K1500 Sierra
    1990 GMC K1500 Sierra
    1988 GMC K1500 Sierra SLE
    1989 GMC K1500 Sierra SLE
    1990 GMC K1500 Sierra SLE
    1988 GMC K1500 Sierra SLX
    1989 GMC K1500 Sierra SLX
    1990 GMC K1500 Sierra SLX
    1988 GMC K2500 Sierra
    1989 GMC K2500 Sierra
    1990 GMC K2500 Sierra
    1988 GMC K2500 Sierra SLE
    1989 GMC K2500 Sierra SLE
    1990 GMC K2500 Sierra SLE
    1988 GMC K2500 Sierra SLX
    1989 GMC K2500 Sierra SLX
    1990 GMC K2500 Sierra SLX
    1988 GMC K3500 Sierra
    1988 GMC K3500 Sierra
    1988 GMC K3500 Sierra
    1989 GMC K3500 Sierra
    1989 GMC K3500 Sierra
    1989 GMC K3500 Sierra
    1990 GMC K3500 Sierra
    1990 GMC K3500 Sierra
    1990 GMC K3500 Sierra
    1988 GMC K3500 Sierra SLE
    1988 GMC K3500 Sierra SLE
    1988 GMC K3500 Sierra SLE
    1989 GMC K3500 Sierra SLE
    1989 GMC K3500 Sierra SLE
    1989 GMC K3500 Sierra SLE
    1990 GMC K3500 Sierra SLE
    1990 GMC K3500 Sierra SLE
    1990 GMC K3500 Sierra SLE
    1988 GMC K3500 Sierra SLX
    1988 GMC K3500 Sierra SLX
    1988 GMC K3500 Sierra SLX
    1989 GMC K3500 Sierra SLX
    1989 GMC K3500 Sierra SLX
    1989 GMC K3500 Sierra SLX
    1990 GMC K3500 Sierra SLX
    1990 GMC K3500 Sierra SLX
    1990 GMC K3500 Sierra SLX
    1990 GMC R1500 Suburban Base
    1990 GMC R1500 Suburban Base
    1990 GMC R1500 Suburban SLE
    1990 GMC R1500 Suburban SLE
    1988 GMC R2500 Base
    1988 GMC R2500 Base
    1988 GMC R2500 Base
    1988 GMC R2500 Base
    1989 GMC R2500 Base
    1989 GMC R2500 Base
    1989 GMC R2500 Base
    1988 GMC R2500 High Sierra
    1988 GMC R2500 High Sierra
    1988 GMC R2500 High Sierra
    1988 GMC R2500 High Sierra
    1989 GMC R2500 High Sierra
    1989 GMC R2500 High Sierra
    1989 GMC R2500 High Sierra
    1988 GMC R2500 Sierra Classic
    1988 GMC R2500 Sierra Classic
    1988 GMC R2500 Sierra Classic
    1988 GMC R2500 Sierra Classic
    1989 GMC R2500 Sierra Classic
    1989 GMC R2500 Sierra Classic
    1989 GMC R2500 Sierra Classic
    1988 GMC R2500 Suburban Base
    1988 GMC R2500 Suburban Base
    1988 GMC R2500 Suburban Base
    1989 GMC R2500 Suburban Base
    1989 GMC R2500 Suburban Base
    1989 GMC R2500 Suburban Base
    1990 GMC R2500 Suburban Base
    1990 GMC R2500 Suburban Base
    1990 GMC R2500 Suburban Base
    1988 GMC R2500 Suburban Sierra Classic
    1988 GMC R2500 Suburban Sierra Classic
    1988 GMC R2500 Suburban Sierra Classic
    1989 GMC R2500 Suburban Sierra Classic
    1989 GMC R2500 Suburban Sierra Classic
    1989 GMC R2500 Suburban Sierra Classic
    1990 GMC R2500 Suburban SLE
    1990 GMC R2500 Suburban SLE
    1990 GMC R2500 Suburban SLE
    1988 GMC R3500 Base
    1988 GMC R3500 Base
    1988 GMC R3500 Base
    1988 GMC R3500 Base
    1989 GMC R3500 Base
    1989 GMC R3500 Base
    1989 GMC R3500 Base
    1990 GMC R3500 Base
    1990 GMC R3500 Base
    1990 GMC R3500 Base
    1988 GMC R3500 High Sierra
    1988 GMC R3500 High Sierra
    1988 GMC R3500 High Sierra
    1988 GMC R3500 High Sierra
    1989 GMC R3500 High Sierra
    1989 GMC R3500 High Sierra
    1989 GMC R3500 High Sierra
    1988 GMC R3500 Sierra Classic
    1988 GMC R3500 Sierra Classic
    1988 GMC R3500 Sierra Classic
    1988 GMC R3500 Sierra Classic
    1989 GMC R3500 Sierra Classic
    1989 GMC R3500 Sierra Classic
    1989 GMC R3500 Sierra Classic
    1990 GMC R3500 SLE
    1990 GMC R3500 SLE
    1990 GMC R3500 SLE
    1990 GMC V1500 Suburban Base
    1990 GMC V1500 Suburban Base
    1990 GMC V1500 Suburban SLE
    1990 GMC V1500 Suburban SLE
    1988 GMC V2500 Suburban Base
    1988 GMC V2500 Suburban Base
    1989 GMC V2500 Suburban Base
    1989 GMC V2500 Suburban Base
    1990 GMC V2500 Suburban Base
    1990 GMC V2500 Suburban Base
    1988 GMC V2500 Suburban Sierra Classic
    1988 GMC V2500 Suburban Sierra Classic
    1989 GMC V2500 Suburban Sierra Classic
    1989 GMC V2500 Suburban Sierra Classic
    1990 GMC V2500 Suburban SLE
    1990 GMC V2500 Suburban SLE
    1988 GMC V3500 Base
    1988 GMC V3500 Base
    1988 GMC V3500 Base
    1988 GMC V3500 Base
    1989 GMC V3500 Base
    1989 GMC V3500 Base
    1989 GMC V3500 Base
    1990 GMC V3500 Base
    1990 GMC V3500 Base
    1990 GMC V3500 Base
    1988 GMC V3500 High Sierra
    1988 GMC V3500 High Sierra
    1988 GMC V3500 High Sierra
    1988 GMC V3500 High Sierra
    1989 GMC V3500 High Sierra
    1989 GMC V3500 High Sierra
    1989 GMC V3500 High Sierra
    1988 GMC V3500 Sierra Classic
    1988 GMC V3500 Sierra Classic
    1988 GMC V3500 Sierra Classic
    1988 GMC V3500 Sierra Classic
    1989 GMC V3500 Sierra Classic
    1989 GMC V3500 Sierra Classic
    1989 GMC V3500 Sierra Classic
    1990 GMC V3500 SLE
    1990 GMC V3500 SLE
    1990 GMC V3500 SLE
    Shipping Policy
    • Free shipping on orders over $99 (excludes freight shipments).
    • In-stock orders typically ship within 1 to 2 business days. Weekend and holiday orders are processed the next business day.
    • Orders ship from Defiance, Ohio and a nationwide network of warehouses and manufacturers.
    • Items showing an ETA are not in stock yet. ETAs come from the manufacturer and can change.
    • No P.O. Boxes. International orders need a shipping quote, so email us first.

    Read the full Shipping Policy

    Return Policy
    • 30-day return window from the ship date. Returns must be approved first; email sales@berryperformancesales.com with your order number.
    • Items must be unused, complete and in the original packaging.
    • A 20% restocking fee applies, and return shipping is paid by the buyer.
    • Not returnable: installed or modified parts, opened or used programmers and tuners, custom orders, Open Box, and Clearance or Final Sale items.
    • Damaged, defective or incorrect items must be reported within 48 hours of delivery with photos.

    Read the full Return Policy

    Disclaimer

    All products are sold for off-road use only unless otherwise specified. Buyer assumes all responsibility for installation and operation. Seller is not liable for any incidental, indirect, or consequential damages — including engine failure, labor costs, or vehicle downtime — resulting from the use of any product sold.

    By making a purchase from Berry Performance Sales, you acknowledge and agree to abide by the terms and conditions of these Policies.

    For any questions or concerns, please contact us — we’re always happy to help.

    Recently Viewed