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

Proper Parts has re-engineered brand-new housings for these units and we recondition the internal parts.  We've been building these units since 2006. 

Our new transmission housings are manufactured in the USA from extremely durable polyamide with fiberglass fill. The complete unit is assembled, tested, and shipped to you ready to be installed. Guaranteed for Life.


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 15% will be charged.  Your core deposit will be refunded to your original payment method when we receive your core. 

What is an acceptable core?

The internal components are what is important. If the outer case is broken and in pieces, that is not important. We just need the internal parts. If you have any questions, please contact us in advance or send a photo.



Black, Red, and Yellow Driving Gear / 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 were coupled directly to the motor through a black input shaft (or rarely white) and a black rubber coupler. 

NEW COUPLING INCLUDED, Part No. 20113451-S   Proper Parts has re-engineered an improved design that ensures a smooth slip fit to the motor and transmission. One end accepts a 3/8” D-shaft and the other end accepts a 5/16” D-shaft. It is ~1.25” long (31.5mm). The D-shaft openings are very accurate. We manufacture these couplings from a urethane chosen for its hardness and toughness while still having good flexibility. When the seat comes to the end of its track there is no cushion, and this coupling allows the motor to slow down gradually ensuring a longer life for all of the components involved. It is much better than the original.

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 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: alex@properparts.com.

If you have any questions, please contact us.