GM 6-Way Adjustable POWER SEAT TRANSMISSION 1979-1980 20113446 R



Cadillac Buick Chevrolet GMC Oldsmobile Pontiac 1979-1980
The same unit is used on both the driver's seat and passenger seat.

Proper Parts has re-engineered the housings for these units.
Our new transmission housings are manufactured in the USA from extremely durable polyamide with fiberglass fill and are Guaranteed for Life. The internal components are reconditioned and Guaranteed for 5 Years. The complete unit is assembled, tested, and shipped to you ready to be installed.


After installing your new unit, ship your old unit (core) to Proper Parts to receive your core refund. Your purchase receipt must be enclosed to process your refund.

Please do not ship your core until after you've finished installing the new one in order to avoid sending parts that you'll need to keep for installation. 

We ship within 1 to 2 business days. 

Please return your core within 30 days. After 45 days, a late fee of 10% will be charged. Your core refund will be credited to your original payment method when we receive your core in acceptable condition. 

What is an acceptable core?

If the outer case is broken, that is not important. The internal components are what is important. If there are missing or damaged internal components, a pro-rated refund may apply. If you have any questions, please contact us in advance. You can send photos and we'll give you a quote for the core value.

Just because your core is badly broken and in pieces, does not mean you will not receive a full core refund. We just need the internal parts. 



Black, Red, and Yellow Input Shaft 

The original transmission housings were made of nylon. They were white when new but became brown and brittle over time, and many have disintegrated. Most failures are due to the housing breaking apart. There is no new OEM replacement available for this part.

The 20113446 transmissions are coupled directly to the motor through a black input shaft (or rarely white) and a black rubber coupler. The couplers are very durable but do occasionally fail. If you would like to add a coupler to your order, click the link below.


Used OEM Coupler - Part No. 20113451

Please note: Power seat components are designed for normal use. Please move the seat to the desired position and leave it. Repeated up and down or back and forth movement without several minutes to cool down will produce damage.  

Instructions for shipping your core to Proper Parts:

  • Your receipt must be enclosed to process your refund.
  • Ship to: PROPER PARTS, 5725 HARRISON AVE, EXPORT PA 15632.
  • You are responsible for return shipping on your core.
  • Email tracking number to:

If you have any questions, please contact us.