B&M
B&M 20261 Shift Improver Kit Automatic Transmission Shift Kit
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Product Details
Shift Improver Kit Automatic Transmission Shift Kit; Incl. Gaskets/Seals/Drill Bit/Fluid Separators;
Shift Improver Kit 1988 to 1994 Chevrolet, Buick, Olds, Pontiac, GMC TH-400 (3L80) Application: 1988 to 1994 Chevrolet, Buick, Olds, Pontiac, GMC TH-400 (3L80) Recalibrate your automatic transmission for optimum performance and extended life! Select the mode that best suits your application Provides crisp shifts on any stock automatic transmission Eliminates shift overlap and excess wear on clutches and bands due to slippage The B&M Shift Improver Kit the easiest way to get the stout performance you've always wanted out of your automatic transmission - and you get two modes of performance to select from: Heavy Duty, or Street/Strip. It's our least expensive and simplest to install kit. All you need are some hand tools! In the space of an afternoon, you can turn your transmission into a B&M-tuned unit! Ask the thousands of satisfied customers that have installed one in their transmissions! STAGE 1. HEAVY DUTY Firm positive shifts without loss of driver comfort for improved performance in all street vehicles. Recommended for regular passenger vehicles. STAGE 2. STREET/STRIP Provides positive shifts for high performance street use or for competitive events. This level is for the enthusiast who wants the hardest, quickest possible shift.
Fitment: Fits 1988 to 1994 Chevrolet; Buick; Olds; Pontiac; GMC with a TH-400 (3L80) automatic transmission
DETAILS:
Part Number 20261 SPECS:
Automatic Transmission Shift Kit - Shift Improver - TH400 1988-90 - Kit
DETAILS:
- Holley Performance Emission Code 5: This part is legal for sale or use on Emissions Controlled Vehicles; Uncontrolled (Non-Emissions Controlled) Vehicles; and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations
- Automatic Transmission Shift Kit
- Shift Improver Kit Automatic Transmission Shift Kit
- Eliminate Clutch and Band Wear
- Eliminates Shift Overlap
- Eliminates Soft/Sluggish Shift
- Improves Transmission Life
- On Any Stock Automatic Transmission
- Provides Crisp Shifts
- Transmission Removal Not Required
- SHIFT IMPROVER KIT 88-94 TH400
- 20261; Shift Improver Kit; B/M; b and m; transmission; manual; automatic; shift kit; improver; transkit; racing; knob; lever; torque converter
- Auto Trans Shift Kit
Part Number 20261 SPECS:
- Automotive Item Grade: High Performance
- California Proposition 65 Chemical Name 1: Cadmium and cadmium compounds
- Gasket Or Seal Included: Yes
- Instructions Included: Yes
- Package Contents: Gaskets, Seals, Drill Bit and Fluid Separators
- Title: B&M 20261 Shift Improver Kit
- Trans Model: GM- 4L80E (Auto) 4 Speed
- Trans Model: GM- TH400 (Auto) 3 Speed
- Trans Year: 1988
- Trans Year: 1989
- Trans Year: 1990
- Trans Year: 1991
- Trans Year: 1992
- Trans Year: 1993
- Trans Year: 1994
- WARNING CA Proposition 65: No
Automatic Transmission Shift Kit - Shift Improver - TH400 1988-90 - Kit
Vehicle Fitment
Universal or product-specific fitment. Please review the product details and contact us if you need help confirming fitment before ordering.
Product Specs
- Brand
- B&M
- Part Number
- 20261
- Catalog Number
- 001433053
- Product Line
- Automatic Transmission Shift Kits
- Category
- Transmission
- Type
- Automatic Transmission Shift Kits
- UPC / Barcode
- 019695202613
- Length
- 16.90 in
- Width
- 13.95 in
- Height
- 0.50 in
- Weight
- 0.88 lb
- Ship Alone
- No
- Air Restricted
- No
Shipping & Availability
This item is showing available inventory. Most in-stock performance parts ship quickly, but timing can vary by warehouse, vendor cut-off time, holidays, and carrier pickup.
Inventory shown: 3 available as of 6/4/2026.
Lifetime Limited Warranty applies to all B&M shifters, differential covers and cast aluminum pans.
One Year Limited Warranty applies to B&M coolers, shifter related accessories (knobs, handles, etc.), torque converters, flexplates, dipsticks, stamped steel pans and other transmission related accessories (except racing products).
90 Day Limited Warranty applies to B&M transmissions, launch control kits and all electrical components (switches, lights, solenoids).
B&M Performance & Off-Road (“B&M”) extends the following limited warranty to the original purchaser of its shifters, pans, coolers, transmissions, components and accessories (hereafter “products”).
B&M warrants the products mentioned above against defects in materials and workmanship for the period set forth below, when they are owned by the original purchaser and remain installed on the vehicle on which they were originally installed. This warranty is void if the product was not installed properly on the vehicle, was installed on a vehicle for which it was not designed, or was removed from the vehicle on which it was originally installed and reinstalled on another vehicle. This warranty shall not apply to normal wear (bushings, springs, etc.), cosmetic issues such as coatings and material discoloration, or any product that was installed on a racing vehicle (excluding shifters), installed contrary to B&M instructions, or altered, misused, repaired, damaged from an accident, collision, undercarriage road impact or debris, or willful or negligent act.
The warranty set forth herein for all B&M shifters, differential covers and cast aluminum pans extends for a period of the life of the original vehicle the product was installed on. The warranty set forth herein for B&M coolers, shifter related accessories (knobs, handles, etc.), torque converters, flexplates, dipsticks, stamped steel pans and other transmission related accessories (except racing products) extends for a period of one year from the date of original purchase and the original vehicle it was installed on. The warranty set forth herein for B&M transmissions, launch control kits and all electrical components (switches, lights, solenoids) extends for a period of 90 days from the date of original purchase and the original vehicle it was installed on.
To make any claim under the terms of this limited warranty, the original purchaser MUST either return the product to the original retailer or directly to B&M. NOTE: ALL B&M TRANSMISSIONS MUST BE RETURNED DIRECTLY TO B&M. If the original purchaser elects to return the product to B&M directly, he or she must first contact B&M and obtain a Returned Material Authorization (RMA) number. Once the RMA number is received, the original purchaser may return the product to address provided by B&M along with the RMA number and Proof of Purchase of the covered product. The Proof of Purchase must clearly show the place of purchase, purchase price, product purchased, and date of purchase. If upon inspection by B&M the product is found to be defective in material or workmanship, B&M shall at its option, either exchange the product for new product with the same part number or refund the original purchase price.
This warranty is not contingent upon the purchaser’s completion of the Warranty Registration Form found on the B&M website. If however the purchaser completes and submits that form at the time of purchase, B&M will keep that form on file which may serve as an aid in determining warranty coverage in the event of the loss of the original purchase receipt.
B&M’s liability is expressly limited to the replacement of the product or refund of the purchase price as described herein. B&M shall have no liability for the cost of installation or removal of the defective product, the cost of labor or any additional parts required to complete the installation of the replacement product, towing or transportation costs, or return shipping costs. In no event shall B&M be liable for any direct, indirect, special, incidental and/or consequential losses or damages, including but not limited to interruption of business or loss of business or loss of profit or damage to related components resulting from the use of or inability to use the product, or any breach of warranty or any defect in the product, even if B&M shall have been advised of the possibility of such potential losses or damages. Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above limitation or exclusion may not apply to you. This warranty gives you specific legal rights. You may also have other rights which may vary from state to state.
The warranties set forth herein are exclusive and unless otherwise required by applicable law, no other warranties are made by B&M or are authorized to be made with respect to the product.
Reviews & Questions
Real product feedback when available, plus quick ways to get fitment or product help.
Other Popular Automatic Transmission Shift Kits
LMPerformance is pleased to offer you B & M Auto parts to make your car more fun to drive. B&M racing specializes in performance automatic transmissions, torque converters, SFI approved flexplates, legendary automatic shifters, precision manual shifters, and many other transmission products. LMPerformance has chosen B&M racing aftermarket parts for quality and performance knowing that the company has had an outstanding reputation since the 1950's.
B&M invented the racing automatic shifter and offers the widest range of applications, functions and styling in the world. B&M Automatic shifters are easy to install and come with detailed instructions. In Additon, the majority of B & M Auto Shifters are NHRA approved and include safety reverse lock-out. B&M's reverse lock-out eliminates the need for a reverse valve-body. In order to make the installation easier and for the best fit, all shifters except Street Rod Shifters use a heavy duty cable. All B&M Shifters include a reverse or neutral switch.
LMPerformance also carries B&M Supercoolers for your transmission. Why B&M? Because B&M SuperCoolers are 100% aluminum construction. B&M uses stamped plates sandwiched together to create one of the most efficient oil cooling devices available. The B&M Super-Coolers intended for automatic transmission fluid also offer an additional feature known as “Low Pressure Drop”. The B&M SuperCoolers combine improved protection against lube system failure while keeping the required levels of optimal heat transfer.
Do you want to add fluid capacity to your transmission? Check out LMPerformance's offering of B&M Deep Pans. Being able to hold extra fluid means more cooling. More cooling means better efficiency and performance. Increase your transmission's life with a B&M Deep Pan from LMPerformance. B&M parts at the best price.
If you follow the history of B & M you will soon see why their reputation in the automotive aftermarket industry is secure and impressive. B & M’s founders have a background in racing and as such knew where to start when it came to identifying areas that needed improvement. They are responsible for impressive new ideas in the performance world, ideas like HYDRAMATIC for racing applications and shifters to go along with that, then race converters, shift and transmission improving kits and the list goes on. If you follow the racing circuit then we are sure you are familiar with B & M and its contributions to not only the racing industry but to the performance car industry as well.
If you are in search of a performance shifter for your Firebird, GTO, Mustang, Corvette or Camaro then you are certain to find that the B & M shifters are the kind of product you have been craving with easy installation and with most being NHRA approved and featuring safety reverse lock-out. Couple all of this with a competitive price and free shipping from LMPERFORMANCE and you can’t go wrong. Looking for more performance parts? Check out our Corsa Performance Exhaust parts here.
Review our return, cancellation, shipping, warranty, and product image policies before ordering.
Contact us with questions before ordering
California Residents: Prop 65 WARNING: This product MAY contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling. For more information, visit www.P65Warnings.ca.gov
California Residents: TIRE WARNING: LMPerformance will not ship Tires to California.
Legal: Some or all of these parts may not comply with Federal, State, Province, and/or Local laws, ordinances, and regulations. Buyer takes all responsibility to ensure that any modifications or upgrades that have done conform to all applicable laws and regulations for road use, especially pertaining to safety and emissions. LMPerformance is not responsible for buyer not complying with Federal, State, Province, and/or Local laws, ordinances, and regulations. This policy shall be in force for all past, current, and future purchases from LMPerformance, Inc. LMPerformance will not ship ANY non-CARB compliant products to California where California requires products to be CARB certified such as Catalytic Converters and Induction Kits.
Free Shipping: Please note FREE Shipping refers to shipping within the contiguous continental US only. All other locations extra. Some items that require Truck Freight Delivery will require a Truck Freight surcharge. This surcharge is still a discounted shipping amount that is lower then the actual truck freight shipping charge that is charged to LMP. LMP will try to still give the lowest price possible for truck freight items.
Images: Images may be a representation and may not reflect the actual product. Examples would be SPEC stage 3 clutch kits which all use the same photo.
TYPOS: LMPerformance tries to present the best most accurate information on our website. Sometimes we get mistakes in product information sent from vendors such as typos. We can not be responsible for these typos, if you see something that does not look right please let us know before ordering so we can double check for you first. LMPerformance will not pay for typos in any way, monetarily or otherwise.
Price Errors: In the event that a product has mistakenly been listed at an incorrect price, We reserve the right to refuse or cancel any orders placed for product listed at the incorrect price. We reserve the right to refuse or cancel any such orders whether or not the order has been confirmed and your account charged. If your payment type has already been charged for the purchase and your order is cancelled, a full refund to your orignial payment method in the amount of the incorrect price will be issued.
Special Order ITEMS: Some items are Special Ordered and may not be returnable, or even cancellable as they are going into production specifically because you ordered them. Special Ordered items can have a 5-35% cancelation fee.
Cancellations: Instock orders cannot be canceled due to our automated ordering & fast shipping system. To keep our prices low, all cancelations are subject to a 5% cancelation fee to cover transaction processing fees. We reserve the right to charge up to a 10% cancellation fee for cancelled orders due to merchant fees, Special Order fees and the cost of processing and shipping orders.When you request a cancellation of an order or a part, please note that it may take time for a manufacturer to cancel an order if the order is drop-shipped. We also have to confirm that the product has not shipped. If the product has shipped then this must be processed as a return.Also note that sometimes products ship more quickly than expected, so we recommend that you do not purchase alternative products until receiving final confirmation of the cancellation.
Returns: We cannot accept returns on parts that have been used or installed. No returns will be accepted after 30 days. All Returns must be in original packaging. Prior authorization must be given before any return can be made. Up to a 25% Restocking Fee may apply. Special Orders may be subject to Additional Manufacturer Restock Fees as well. Shipping cost will not be refunded.Hoods as well as PCM Programmers may not be returned unless defective and only for replacement. ALL returns must be first filed using our online form found here: https://www.lmperformance.com/returns.
Lost Order Claims All lost order/package claims must be made within 5 days of the shipping date or tracking information delivery date. All claimes made after this date will not be accepted due to Shipping companies policies of filing loss claims.
Damaged Items or Incorrect Items: Please contact us right away if your item has been damaged in shipping or are incorrect. Please note that we will ship replacement items the same method of shipping the order was originally placed for. LMPerformance can not ship packages overnight at our cost if the original shipping was not also overnight. Claims must be filed in order for replacement parts to be shipped.
Warranties:Any warranty claims must be placed with the manufacturer. All of the products sold by LMPerformance, regardless of the manufacturer, are designed for Racing and Performance applications. Many of our manufacturers offer NO WARRANTY on their products, either stated or implied, due to the unusual stresses placed on the parts and because we have no control over how they are installed and used. Many of these products are designed for off-road use only and are not legal for use on public highways. If you have a question about the warranty on a specific product, please e-mail or call us. Buyer assumes all risk and liability associated with these products.
Installation: We are not responsible for or any costs associated with the installation or the improper installation of any products. Purchaser assumes the risk associated with the installation of products. We, along with the manufacturer of each product are not responsible for any direct or indirect damage to the vehicle, personal, or costs incurred from the use of products.