How To Identify A 1955-1957 Chevy Electric Wiper Motor

Posted by Brad Dunn, Pete Swatzky & Denny Williams on 9/24/2013 to Tech Articles
[This article was first published in Bow Times, June 1993, pp 4-6] 

1955-1957 Chevy Electric Wiper MotorThere has been some confusion as to what motor is correct for a specific 1955/1956/1957 car because up until now, nothing has been published on identifying the correct motors. Another reason for the problem is that all of the motors listed in Table #1 will bolt into place on any passenger car firewall and function properly. So, when someone needed another wiper motor, or wanted to change from vacuum to electric, they simply unbolted the "old" and replaced it with one of those listed.

This month's TechCheck will explain, and show what is correct for your 1955/1956/1957 passenger car. There will not be a lot of narrative because the photos will do most of the "explaining."

Table #1
Model Year ApplicationMotor #
1955 -----------------------5047787
1956 - 1st Style ----------- 5047906 (Time change from 1st style to 2nd style unknown.)
1956 - 2nd Style -----------5047905
1957 - 1st Style ----------- 5047981 (Used until Dec. 1,1956)
1957 - 2nd Style -----------5047988* (Used starting Dec. 1,1956)
1955 - 57 Replacement---- 5044280* (Replacement only)
* Has "slow park" feature. Here is what the 1957 Service News says about the "slow park" feature. "As the name implies, a new style drive gear is incorporated in the wiper which returns the wiper blades to the lower edge of the windshield glass very slowly when the wiper is turned off."

1955 Wiper Motor #5047787 (See Photo #1.)
Several items to notice about the "787":
  1. Square cover (Held in place with slotted, round-head screws)
  2. Part # stamped in area pointed out with arrow A.
  3. Retaining ring pointed out with arrow B (Any of these wiper motors with the retaining ring will not have the "slow park" feature.)
  4. Riveted, black ground wire with straight bayonet end. (All of the original passenger wiper motors had this type of ground.)
  5. Most had the "offset" nylon switch, but some had the "straight" nylon switch found on the 1956 wiper motors.
       6.   This motor happened to be built December 16,1954.
       7.   No gusset in area pointed out with arrow C.

1956 1st Style Wiper Motor #5047906 (See Photo #2.)
Several items to notice about the "906":
  1. Square cover (Held in place with slotted, round-head screws)
  2. Part # stamped in area pointed out with arrow A (Screw many times covers the 6 of the part #.)
  3. Retaining ring present - no "slow park" feature
  4. Will also have the riveted, black ground wire with straight bayonet end.
  5. "Straight" nylon switch
  6. No cast aluminum gusset in area pointed out by arrow B
1956 2nd Style Wiper Motor #5047905 (See Photo #3.)
Several items to notice about the "905":
  1. Switch cover has one rounded corner (Held in place with slotted, round-head screws.)
  2. Part # stamped in area pointed out with arrow A
  3. Retaining ring present - no "slow park"
  4. Also has riveted, black ground wire with straight bayonet end.
  5. "Straight" nylon switch
  6. Notice cast aluminum gusset pointed out by arrow B
1955/1956 Wiper Motor #5044280 (See Photo #4.)
Several items to notice about the "280":
  1. This is a correct motor for any Original Class 1955/ 1956/1957 - it was, and is just a replacement for the original 1955 & 1956 motors.
  2. Switch cover has one rounded corner.
  3. Part # stamped in same area as "905".
  4. No retaining ring, thus this motor does have the "slow park" feature. (See Arrow A.)
  5. Has riveted, black ground wire with straight bayonet end
  6. Used the "straight" nylon switch like the "905."
  7. Has cast aluminum gusset like the "905."
  8. Notice 1962 production date on the "280" that we photographed. (See Photo #5.)




1957 1st Style Wiper Motor #5047981 (See Photo #6.)
Several items to notice about the "981":
  1. Switch cover has one rounded corner like the "905" and "280."
  2. Part # stamped in same area as "905" and "280."
  3. Has retaining clip - no "slow park" feature.
  4. Uses a straight nylon switch with metal cable retainer with slotted screw and nut. (See Photo #6A.) (Different switch than used in the "905", "906" & "280.")
5.   Has riveted, black ground wire with straight bayonet end.
6.   Has cast aluminum gusset like the "905" and "280."
7.   Used for 1957 passenger cars through November 1956.
 






1957 2nd Style Wiper Motor #5047988 (See Photo #7.)
Several items to notice about the "988":
1.Switch cover has one rounded corner like the "981"
2.Part # stamped in same location as "981"
3.Unlike the "981" the "988" does not have the retaining clip, thus it does have the "slow park" feature.
4.Uses the same nylon switch as "981"
5.Same black ground wire as the rest.
6.Has cast aluminum gusset as the "905," "280" & "981."
7.Used on 1957 passenger cars starting in December 1956.

End Case Screws (See Photo #8.)
The 1955 and 1956 wiper motors (#5047787, #5047906 & #5047905) used slotted, round-head screws to secure the end case. The 1957 wiper motors (#5047981 & #5047988) use hex-head bolts to secure the end case.





Fiber Cover (See Photo #9.)
All of the original electric wiper motors used a small fiber (cardboard-type) cover over the drive mechanism block to take up the slack in the wiper drive drum mechanism. This kept the wiper motor quieter when in operation.





Mounting Brackets (See Photo #10.)
The 1957 (2nd Style) "988" has a mounting bracket that will NOT tilt the wiper motor quite as much as the other original electric wiper motors ("787," "906," "905" & "981"). With this new bracket, the distributor cap could be removed more easily. Notice the greater angle on the left wiper motor, the "988" is on the right.




Power Leads (See Photo #11.)
All original electric wiper motors had brown power lead wires. The 1955 & 1956 wiper motor leads had straight fork connectors with a black plastic insulator, while the 1957 wiper motor leads used a 90-degree fork.





Armature Adjusting Screws (See Photo #12.)
Most of the time the hardware that adjusts the end play of the motor armature are as pictured, but not always.

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Comments

Bob Kemmler Date 2/7/2014

Where can I order the screws for the end case and what size are they

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