8L90 Archives - Transmission Digest
New GM 8L45, 8L90 Zip Kits

Sonnax has introduced two Zip Kits that target the root cause of multiple shift-related complaints and converter-related complaints, respectively, by sealing the critical circuit pressure losses in the GM 8L45 and 8L90 valve body. Kit #8L45-8L90-SHIFT-ZIP helps prevent pressure loss within the signal accumulator, clutch control and 1-3-5-6-7 accumulator piston circuits. Kit #8L45-8L90-TCC-ZIP helps prevent

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

8L90E Coated Torque Converter Friction Ring

Alto Products recently introduced its GM 8L90E Coated Torque Converter Friction Ring (10 notch design). The ring features its G3­ Hi-Performance material (p/n T2464G3). For more information, visit www.altousa.com.

GM 8L45/90 1-3-5-6-7 Accumulator Piston Kit

Sonnax has introduced a new drop-in Zip Valve kit. The 1-3-5-6-7 accumulator piston kit (p/n 154740-15K) eliminates leaks in GM 8L45/90 units. This kit restores normal shift operation and feel while protecting against premature wear for lasting results.

TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints

Sometimes attention to the smallest of items can save you big dollars.

GM 8L45, 8L90 Signal Accumulator Piston Kit

Sonnax has a new drop-in Zip Valve product: signal accumulator piston kit (p/n 154740-06K). Including four piston sets that fit any of seven locations in GM 8L45 and 8L90 units, this kit allows bores to be reconditioned quickly and easily with no reaming required. The hydraulic integrity of the VFS signal pressure circuits are re-set.

GM 8L45, 8L90 O-Ringed End Plug Kit

Sonnax has introduced a new drop-in Zip Valve product: O-ringed end plug kit (p/n 154740-17K). This easy-to-install kit puts an end to leaks, restores hydraulic integrity and renews shift operation in GM 8L45 and 8L90 transmissions.

ATI’s All-New 8L90E Corvette 300M Output Shaft

ATI Performance Products, Inc has introduced a new 300M Output Shaft (p/n 704050) for C7 Corvettes and ZR1s equipped with the 8L90E transmission. This brand-new 8L90E output is a direct OEM replacement and requires no modifications. ATI Performance Products, Inc. specializes in producing and maintaining high-performance products for street and strip applications. For more, visit

8L90 Friction Linings

New GM 8L90 friction linings from Tri Component.

GM 8L90 – The Other 8 Speed Automatic: Part 1

One example of how time flies by is the fact that there has been an eight-speed automatic transmission on the road since 2007. The Aisin Corp. beat everyone to the punch when they developed the AA80E for use by Lexus. The next eight-speed automatic to hit the streets came from ZF in late 2009 and was used by Audi and BMW. Even Hyundai got into the mix by releasing the A8LR1 and A8TR1 in 2011.