Shift Improver Kit for GM TH400/TH375/TH475

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Drivetrain› Automatic Transmissions and Components

B&M Shift

Shift Improver Kit for GM TH400/TH375/TH475

Name: Shift Improver Kit for GM TH400/TH375/TH475
Brand: B&M Shift
SKU: 20260

$69.44

SKU: 20260

Free Shipping over $200

$100 Minimum Order

Non-Returnable Item

DIY PRO SHOP

Easy — 1–2 hours

Overview

It offers two stages to fit your needs: RV/Towing and Street/Strip.

Installation is straightforward and can be completed with basic hand tools. This kit recalibrates your automatic transmission for crisp shifts, improved performance, and extended transmission life, while eliminating shift overlap.

Show original supplier description

The B&M Shift Improver Kit offers a solution for recalibrating your 1965-1987 GM TH400, TH375, and TH475 automatic transmissions. This kit provides two distinct recalibration options, allowing you to tailor the transmission's performance to your needs. It also helps to reduce excess wear on clutches and other internal components by eliminating undesirable shift characteristics. Installation is described as achievable within a few hours for those who carefully follow the provided instructions. It is important to note that this kit does not fit transmissions built after 1987. For vehicles manufactured in 1988 or later that may have had a transmission replacement, it is crucial to check the Julian date stamped on the transmission's identification tag to ensure compatibility.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

Brand	B&M Shift
Part Number	20260
Category	Drivetrain

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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