Backing Plate

Sonnax®

Intermediate Clutch

TH400 4L80E

GM Chevy Buick Cadillac Oldsmobile Pontiac

.375", Heavy Duty

1965-1998

GM ’98-earlier 4L80-E transmissions can suffer intermediate backing plate breakage, clutch failure and case lug blow out when pressures are increased for more clutch holding capacity. Sonnax® .375" thick, heavy duty intermediate clutch backing plate 34144HD-01 is made of billet steel to withstand higher pressures and features lugs around the entire perimeter to improve durability. This plate can also be used to upgrade the .430" thick plate in TH400 transmissions, allowing for more intermediate clutch setup options.

Stronger material and full set of case lugs prevent failure at higher pressures

Compatible with OE and aftermarket cases

Use with Sonnax® case saver retainer 34762-10 to eliminate OE case lug blow out, no plate modifications required

Allows for more options when expanding TH400 intermediate clutch capacity