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TCI Automotive 399753 LS1 Engine to GM Auto Transmission Adapter

TCI Automotive 399753 LS1 Engine to GM Auto Transmission Adapter
TCI Automotive 399753 LS1 Engine to GM Auto Transmission Adapter
TCI Automotive 399753 LS1 Engine to GM Auto Transmission Adapter

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Q & A

What's in the Box

If you want to bolt a TH350, TH400, Powerglide, and 700R4 transmission up to your LS-Series engine, you need this kit. The spacer properly positions the flexplate and supports the converter hub. For Turbo 350, Turbo 400, and 700R4 transmission application.

SFI 29.1 approved. Dual bolt patterns: stock LS-Series and small GM bolt pattern.

Kit includes:

  • dual bolt pattern SFI rated flexplate
  • flexplate spacer
  • flexplate to crankshaft bolts
  • instructions

Note: Requires a 10-1/2" bolt circle converter.


  1. Fits internally balanced Chevy 4.8, 5.3, 5.7, 6.0 LS1/LS6-series V8 engines.
  2. Flexplates are .035" thicker than stock and the starter ring is welded to both sides of the flexplate for additional strength. Constructed from a high tensile strength material these flexplates resist elongation and cracking. All 168 tooth flexplates are sized for stock 3/8" mounting bolts and can be easily drilled for 7/16" diameter high performance torque converter applications and are SFI 29.1 approved.

You may also be interested in:

LS1 Motor Mount Adapters
(Part #91618016)

These billet aluminum adapters allow you to put an LS1 where a S/B Chevy would mount. They bolt to the sides of your LS1 and accept standard S/B Chevy mounts. Metric and Standard hardware included.

  • Constructed from .383" thick aluminum
  • LS1 bolt pattern is 4 3/8” horizontal and 3 1/16” vertical
  • Triangular bolt pattern for the standard SBC motor mount
  • Locates LS engine 1 3/16" forward from the original SBC placement

Note: These motor mounts may require you to move your transmission mount forward in some applications.

916-18016 Instructions (PDF)

B&M 113001 GM TH350 Transmission and 2400 Stall Converter Kit
(Part #200350)

These B&M Street/Strip Turbo 350 automatic transmission and converter combinations are designed to be used in street rods and muscle cars. The included Tork Master 2400 converter has a higher stall speed (2300-2500 RPM) which allows you to run a little more cam without having the car pulling on the brakes all the time. This TH350 transmission is ideal for use behind small block Chevy engines with 230 ft. lbs. of torque at 2500 RPM. It has a 2:52 first, 1:52 second and 1:1 high gears. Uses the short 6" tail shaft and has an adjustable modulator and B&M internals. Ships by truck.

B&M TH350 features: 

  • 2:52 1st gear, 1:52 2nd gear
  • Extra wide direct drum bushing
  • Machined forward & direct pistons
  • New kickdown band with welded anchors
  • New intermediate & low roller clutches
  • All new B&M high performance friction plates, thrust bearings & races
  • New adjustable modulator, detent control link with new breather & filter
  • Recalibrated valve body Hardened intermediate outer race
  • Dual piston apply feature on 2-3 shift to increase torque capacity

Tork Master 2400 Converter features:

  • New alloy steel pump drive tube
  • Needle thrust bearings when factory equipped
  • New thrust washer between turbine and cover
  • Pressure tested and fully balanced 
Aluminum Heatsink Transmission Cooler, 12 Inch
(Part #91023112)

The conductivity of aluminum and added fins make these the best choice for performance and price. Includes hose barb fittings.

  • Compact & efficient size
  • All-aluminum design for maximum heat transfer
  • Easily mounts to most frame rails 
  • Includes two hose nipples to fit 3/8" hose
1997-Present GM LS1, LS2, LS6 Steel Flexplate, Platinum Series
(Part #57534610)

Platinum Series 1997-up LS1, LS2, LS6 engine flexplates raise the bar in the high performance industry. The combination of top quality and reasonable pricing sets new standards.

These Platinum Series Flexplates are engineered to handle extreme duty applications and designed to take the punishment of today's high horsepower engines. The 4mm thick centerplate provides a solid foundation for these new designs. Ring gears are precision welded to meet SFI specifications, utilizing robotic machiner and cold-welding process. These flexplates are engineered for excellence and are rigorously inspected throughout the manufacturing cycle to ensure that our customers receive the highest quality parts.

  • SFI 29.1 certified
  • This flexplate works for Turbo 350/Turbo 400 transmissions as well as the older 700R4 and 4L60 transmissions
  • Direct bolt on component
  • Forged one-piece steel ring gears
  • 0.035" thicker than stock flexplates
  • Constructed from cold-rolled premium steel
  • Long lasting platinum finish that helps prevent rust
  • Features double welded ring gears for added durability

For the 1997-Present GM LS1, LS2, LS6 engines.

GM TH350-TH400 LS Crank Converter Sleeve Adapter
(Part #57518346)
                        This adapter sleeve will connect the GM LS series Xtreme Duty Flexplate with a 4mm thick centerplate to an older GM Turbo 350 or Turbo 400 transmission. For TH350 or TH400 transmission application.
ARP Fasteners 244-2901 Chevy Gen III/LS Flexplate Bolts
(Part #1012442901)
                        Flywheel bolts play an important role in the  performance and safety of race cars and street machines alike. That’s  why the fastener experts at ARP develop special bolts that are far  superior to OEM hardware. Forged from aerospace alloy and heat-treated  prior to thread rolling and machining.
  • Fits Chevrolet Gen III/LS Series Small Block
  • Exclusive, flat, 12-point head design
  • Larger than stock shank diameter for increased strength and improved flywheel register
  • Originally developed for NASCAR Winston Cup competition
  • Has a 200,000 psi rating
  • Set of 6
  • M11 x 1.5
  • .880" under head length