My drivers side wiper blade hits and goes over the A pillar trim.
I maxed out the adjustment in the center and it still goes over.
The arm measures 16 & 1/2 " from where the wiper blade connects to the arm to the pivot point on the bottom.
Do I have an arm from a different year?

 

Hi PB,
There's a screw known as screw "A" on each arm. It controls the angle of the arm extension and is used to adjust that angle so the blade doesn't sweep too far and go over the ss trim.
Easy Adjustment!
Regards,
Alan

You see it on the side of the arm in this picture. It's just to the right of the washer tube clip.


This is the underside of the arm with the 'cover' removed and shows the mechanism that the screw controls to change the angle of the end of the arm.

 

Hi Alan 71,
I just looked and I don't have an adjustment screw.
Maybe 71 & 74 are different.
Thank for the suggestion.
Pete.

 

Hi again,
just saw your second picture, I have a rivet in that area.

 

The original problem was that the part on the left side of the arm where the spring connects broke.
I found a used wiper arm that measures and looks the same as the broken one.
The old one went over the A pillar also and while I was at it I thought that I could fix the problem but not!
You have an adjustment screw I have a rivet there.
Thank again for your help, Pete.

 

Pete-

Your arm adjustment is different than Alans. I'm pretty sure 1972 was the last year for the dreaded screw A.

Willcox

 

Hi Pete,
Sorry for the false trail!
Regards,
Alan

 

Not a false train I just have the wrong year.
Your pictures are very helpful so thanks for posting them.

Willcox Corvette:
Your instructions are spot on, I just have the wrong arm.
I looked at you web site and saw 69-74 Early and 74 Late-82.
My serial number is 26002 and the trim tag indicates May 1.
My plan is to find another 74 and confirm the correct arm before I order new ones.
Thanks to you to for the help,
Pete.

PS: Considered bending the arm but it's not magnetic (pot metal?) and I don't think that will work as I am very good at breaking stuff.

 

Pete-

I don't remember even the early cars having a different arm... but I just looked at some stuff and it does. I know the brass tube stopped in 1973 so... I'm a bit miffed at what early and late difference were, I'll have to look at this tomorrow.

Willcox

 

Hi Ernie,
I have the utmost confidence that you will help me figure this out.
Thanks again,
Pete.

 

Here is what I found out today.

The early 1974 cars used the 1973 style wipers that had the brass tubes and the are tilting screw A. The late 74 used the same arm with no tilting screw and rubber hoses. The arm itself was close to the earlier arm but there were other differences.

What is confusing about this is that the linkage transmission was the same for both the right and left transmissions yet, the 1974 and newer car adjustment was done at the transmission nuts and not at the wiper arm screw as with the previous year.

I talked to a few people here about this but have no verification as to when the switch was made but everyone said they thought only the very early cars used the metal (brass tubes) which would push your car past this time line. The last revision I see on the AIM was made to the dimension and this was done 11-8-1973 so that would be a pretty early running change. The AIM shows the early style blades and arms.. The latest revision I've found in a 74 AIM and I just scanned it quickly was one done in 1-8-74. But that doesn't mean anything considering the books were a hodgepodge of information.

I have to believe that GM figured there was enough clearance in the wiper arm transmissions to accommodate the revision in the wiper arms thus eliminating the Screw A from existence. (Personally Screw A is a life saver when you have these issues). However, with the arm you have you too should be able to adjust out the issue unless the transmission or arm is bent.

The only used arms I have here are on my 70 lt-1 I pulled a set of the new 74 early arms and they do have the screw A. I have new early arms on the shelf.

Ernie

Below you'll find each year with the arm part number and the transmission number.

Year: arm lh arm rh trans lh trans rh

68 3930355 3942736 4918792 4919036
69 3956246 3965154 4918792 4919036
70 3956245 3965154 4918792 4919036
71 3956245 3965154 4918792 4919036
72 3956245 3965154 4918792 4919036
73 3956245 3965154 4918792 4919036
74e 3956245 3965154 4918792 4919036 last rev 11/8/1973
74-82 355339 333340 4918792 4919036

 

Hi Ernie,
Thank you for the research it is not in vain. I'm very tempted to order the early arms with the "A" screw however that may not be prudent based on your comment 'unless the transmission (Linkage) or (wiper) arm is bent'.
There is a car show with several C-3's each Friday at a hamburger joint in Stanley, NC I will go there and compare mine to theirs.
Thank you again,
Pete.

 

My pleasure Pete-

I'm curious as to the running change time line. Wonder if others with a 74 might chime in with which arms they have.