1878-82 Turn Signal, Dimmer Pivot Confusion

[Jim S.]

NOTE: The 1977 Corvette steering column was redesigned where both the windshield wash/wipe switch and the headlight dimmer were included on the turn signal lever. This was a one year only design and not the one that I am going to discuss.

Starting in 1978 the Corvette column the wiper switch was returned to the dash. But the headlight dimmer was still included on the steering column on both the standard (non-adjustable) and the T&T columns.

There is a common problem that seems to be prevalent through most Corvette supplier catalogues. There is mention of 1978 Early and 1978 Late Turn Signal Switches. They make mention of "bent" and "straight" turn signal switch levers. Also there is a difference between 1978 Early dimmer pivots and 1978 Late pivots.

On the 1978 through 1982 Corvette steering columns, the turn signal lever snaps into a pivot assembly that is inside the steering column head. The pivot assembly then connects to the turn signal switch with a small cross-over arm. So the turn signal switch doesn't care what type lever is being used. The bent and straight levers must match up to the type of dimmer pivot that is in the column NOT the switch itself.

Here is the killer part of the problem; there are pivots that have a shallow (21 degree) angle so that the turn signal lever needs to be bent in order to end up close to the steering wheel rim and there are pivots with a steep (46 degree) angle where a straight lever is used. My information shows the 21 degree angle pivot being used 1978 and 1979. The 46 degree pivot starts the 1980 model year. (But could it have been pulled ahead into 1979?)

There are differences between 1978-79 and 1980-82 turn signal switches in that 1980+ switches have extra wires for cornering lights. The switches with the extra wires can be used in the older Vettes (the wires just don't have a vehicle cornerning light harness to connect to).

The last confusing part to this whole saga is the fact that 1978 Early pivots attached inside the column head by means of a special screw. Late 1978 pivots attached inside the column head by means of a pressed-in pin. You need to know what type pivot and connection that you have because they do not interchange.

So I am suspecting that a long time ago, someone (maybe in the Chevrolet Service Department) may have gotten confused between levers, switches, and pivots and how they acted with each other. The suppliers picked up on the error and so we have confusion today.

Hopefully you might be able to describe to your supplier tech, exactly what you might need (i.e early, late, special screw, pressed-in pin, straight versus bent levers, and worst of all 21 versus 46 degree pivots.)

If anyone (Joe Lucia?) can supply any further info on this confusing subject, it would be greatly appreciated.
Jim

[Jim S.]

Re: 1978-82 Turn Signal, Dimmer Pivot Confusion

Can anyone help me on this posting on the various dimmer pivots and turn signal levers?

BTW, I am writing a paper (complete with drawings) that tries to explain the problem more fully.

Jim

[Scott O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Hi, Jim
I think I have an answer for you. My Car built 2/78 has the early pivot joint. Mine was broken when I bought the car, located a NOS in the bag. Hopefully the attached pictures will answer your questions!
Your Steering column articles have been a big help to me
Let me know if you need more pictures
Scott

[Roger O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Jim , It sounds as if there is more than 1 question above.
I have one of the early pivots with the special screw that Scott posted above. I can measure,take pics,or even send it to you if you would like to have one in hand.
I also have a 78 column here I can pull apart.

Looking at the 2 pivots , it appears if you have the early screw type you can make the later pin type work if you still have the special screw.

Roger

[Jim S.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Scott,
Thank you for the very informative pictures. As usual someones helpful pictures present still another question.

Here is the address for a chart of the various turn signal levers that I was able to find that were used on C3 Corvettes. I utilized information from Joe Lucia, from various supplier catalogues, and from drawings to create the chart.

http://jimshea.corvettefaq.com/wp-content/uploads/2010/07/1968-82-c3-turn-signal-leversrev14jl2010.pdf

The levers with cruise are pretty straight forward. With the plug-in levers with cruise (1978 and later), when the dimmer pivot angle inside the T&T column was increased (from 21 degree to 46 degrees), the bend in the lever was eliminated. The following address will take you to a paper with drawings that may help in explaining this subject.

http://jimshea.corvettefaq.com/wp-content/uploads/2010/07/corvettestrgcolumndimmerpivotconfusionrev14jl2010.pdf

Remember that the steering column was shipped to St.Louis or Bowling Green, it did not know if it was to be assembled into a car with (or without) cruise. Your 1978 Early T&T column (without cruise) has the shallow pivot angle and your lever has a 26 degree bend in the lever. (I measured your photo.)

However, there is only one service lever from 1978 through 1982 that I was able to find that was available without cruise. Doc Rebuild shows the lever as being straight. I am very sure that the straight lever must be correct because installing a bent lever (like yours) with a 26 degree bend added to a 46 degree pivot angle is going to place the end of the lever very close to being parallel to the steering column centerline (26 + 46 = 72 degrees) and locate the end almost on the underside of the steering wheel.

Chevrolet must have figured that a straight service lever installed on a 1978 T&T column (with a shallow pivot angle) would be acceptable even though the tip of the lever would be located a pretty good distance from the steering wheel rim. Your lever must be quite rare because there is (and possibly never was) a bent service part for the standard column without cruise.

Jim

[Jim S.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Roger,
Thank you for the kind offer(s). I was thinking about trying to obtain the actual drawings of the 1978 Early and 1978 Late dimmer pivots. However, now that Saginaw Steering Gear/Delphi/Nexteer is being sold by General Motors to the Chinese I am quite sure that those kind of favors are going to become very difficult if not impossible to obtain.

Interesting observation that the pressed-in pin to hold the dimmer pivot (1978 Late) to the turn signal switch cover might actually work with the dimmer pivot with the screw attachment (1978 Early).

Jim

[Scott O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Hi,Jim
Going on memory here
I don't believe the early/late pivots are interchangeable, here's why.
At the time Vendors were listing the late pivot but not the early one (NA)
I was able to locate an early NOS pivot ($150) and a late used pivot ($50).

Eyeballing the 2 pivots side by side, it was determined needing to locate a late style Does Skin turn signal switch cover housing in the same 8/10 condition as mine to use the late pivot. What I remember was the pin diameter and pivot width may have both been different
However I did not have both turn switch cover housings to compare
At that point the early style was the way to go for me
If you need to borrow a broken early pivot to compare, let me know
Thanks, Scott

[Jim S.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

There were definately two turn signal switch housings. The early one with the threaded housing. The later one with pivot diameter(s) for the press fit pin. It sounds from your description that the actual pivot diameters changed from the screw retained to the press fit pin.

It sounds as if we have access to the early pivot that is screw retained (both Roger and Scott have one.) So what we need is a comparison to the later pin retained pivot.
Jim

[Roger O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Jim , if you look at pic #2 my first thought was, this is a no brainer,just drill the pin type larger to accept the old threaded screw. But the large end under the hex head is not the problem,the problem is the smaller end of the threaded type verses the larger pin type. Some shim material could be used if you went this direction or the small end could be welded and turned down or just make a new threaded pin.
My second thought was to install the pin type and push the pin through the threads in the early style housing. I think the threads are 10-28, so I drilled and threaded a piece of 1/2" thick hardwood and tried to slide the pin through the threads. It held moderately well in the wood,I would think if it was metal it might be OK. I hope that wasn't confusing,if it was just ask and I'll try to explain where I was going.
Maybe if I give you some facts about pin sizes it will make things more clear.
The threaded pin- small round end- .179 large round end .343 length 1.310
The round pin - .213 length 1.335
I feel like if the threads in the early housing will hold the pin you could use the pin type on the early housing.
The pivots appear almost identical for the most part.
Pic#3 makes it look like the holes are the same , the difference is on the inside the hole is .033 larger for the pin type pivot ( right in pic ).
Roger

[Scott O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Roger,
I should have bought the early pivot from you!
Wonder why they made the change?
My guess, cheaper to use straight Pin
Scott

[Roger O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Scott,
I would say your guess would be right,its all about money.
Roger

[Jim S.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Roger,
Would you mind if I used one or two of your pictures in my dimmer pivot paper?

I put a protractor up against the computor screen and note that both pivots in the comparison pics are 21 degree pivots. (Of course the screw retained pivot was only available as a 21 degree part.)

Jim

[Roger O.]

Re: 1878-82 Turn Signal, Dimmer Pivot Confusion

Roger,
Would you mind if I used one or two of your pictures in my dimmer pivot paper?

I put a protractor up against the computor screen and note that both pivots in the comparison pics are 21 degree pivots. (Of course the screw retained pivot was only available as a 21 degree part.)

Jim

Jim,
That would be fine , if you need other pics just let me know.
Roger