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

(GMC G2500 1988-90, K1500 1988-90, C1500 1988-90, K2500 1988-90, Jimmy 1988-90, C3500 1988-90, K3500 1988-90, C2500 1988-90 + 56 more models)

Part of: B&M Shift Improver Kit for GM Transmissions

Other options in this family: B&M 30262 B&M 50260 B&M 50262 B&M 70239 B&M 10226

Manufacturer

Picture for manufacturer B&M

Part Number

20261
4 reviews
Sale Price

$87.45

In Stock (7)

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Usually delivered within 2 days

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Fitment guaranteed

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Product Details

The B&M 20261 Shift Improver Kit is engineered to eliminate soft, sluggish shifts in GM TH400 and TH475 automatic transmissions. This performance upgrade delivers crisp, firm shifts by recalibrating valve body pressure and eliminating shift overlap that causes power loss and transmission wear.

Key Features:

  • Eliminates shift overlap for improved acceleration and reduced clutch wear
  • Provides noticeably firmer, more responsive shifts at all throttle positions
  • Easy installation using basic hand tools—no special equipment required
  • Ideal for street/strip performance, towing applications, and off-road use
  • Includes all necessary components for valve body modification
  • Backed by over 65 years of B&M performance transmission expertise

This shift kit is designed for enthusiasts who demand better transmission performance without a complete rebuild. By modifying the hydraulic circuits in the valve body, the B&M 20261 delivers quicker, more positive engagement that improves overall drivetrain efficiency and reduces heat buildup during hard acceleration or heavy loads.

Products specifications

Fits

GMC G2500 1988-90, K1500 1988-90, C1500 1988-90, K2500 1988-90, Jimmy 1988-90, C3500 1988-90, K3500 1988-90, C2500 1988-90, G25/G2500 Van 1988-90, P3500 1988-90, G3500 1988-90, G1500 1988-90, R1500 Suburban 1988-90, V3500 1988-90 + 50 more models

Package Contents

Gaskets, Seals, Drill Bit and Fluid Separators

Title

B&M 20261 Shift Improver Kit

Prop 65

Yes

California Proposition 65 Chemical Name 1

Cadmium and cadmium compounds

California Proposition 65 Chemical Name

Cadmium and cadmium compounds

Gasket Or Seal Included

Yes

Trans Year

1988

Trans Year

1989

Trans Year

1990

Trans Year

1991

Trans Year

1992

Trans Year

1993

Trans Year

1994

Trans Model

GM- TH400 (Auto) 3 Speed

Trans Model

GM- 4L80E (Auto) 4 Speed

Automotive Item Grade

High Performance

Brand

B&M

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

I ordered an AEM intake for my F-150 on Christmas day and received it on the 29th. I would absolutely recommend this site to anyone looking for car parts - they had the lowest price by far and shipped fast. Great job!

Lowest price on the Internet, good packaging and fast shipping.

Great product and speedy service!

A+ part as advertised, quick shipping.

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