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Topic: Installing a generic tilt steering column on my 75 Coupe

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Installing a generic tilt steering column on my 75 Coupe (1/4)
 12/21/19 9:35pm
BillHanna
Standard Member
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Cana, VA - USA

Vette(s):
1975 Stingray 71 350 engine Flat top pistons Sniper fuel injection Hyperspark ignition Vintage Air air conditioning Borgeson power steering box


Joined: 7/3/2016
Posts: 256

My 75 Coupe steering wheel actually rubbed on the top of my legs, so I decided to replace the steering column with a generic tilt setup.

The first step was to find a column that would fit my Vette. Companies like Flaming River and Ididit provide great columns, but they cost over a thousand dollars, and that was a lot more than I wanted to spend. Most of the columns I found for a floor shift did not have the ignition key on the column. I finally found one on eBay from Gilbertsons Machine Shop for less than three-hundred dollars, so I ordered it. This has a one-inch “DD” shaft, while the Corvette has a spline shaft, so I would need an adapter. There are U-joint type adapters as well as “rag-joint” adapters. I decided to wait until the column was in hand to determine which would fit best.

Once the column was here, I measured it and found the 33 inch column was about 8 inches shorter than needed. I ordered a ¾ by 16 inch “DD” shaft to cut to length to bridge the gap. Since the column comes with a 1 inch “DD” shaft, I ordered a 1 inch to ¾ inch “DD” universal joint, and a ¾ inch “DD” to ¾ inch 30 spline u-joint to connect the ¾ inch “DD” section to the steering box.

The next step is to remove the stock steering column so I can measure and make brackets to connect the new column to the floor, as well as a bracket to connect it below the dash (I could not find any made for the C3). The existing steering wheel was a bit too close to the driver, so I will make the new column fit a bit further away.

After pulling the steering wheel hub from the existing column, I found that the hub will fit the new column. This was a relief because I had searched previously for hubs and none seemed to fit a stock Corvette steering wheel.

Once the old steering column was out, I could see that it would be easier to make new brackets rather then try to salvage the ones from the old column. For one thing, the bracket for the under-dash mount would interfere with the ignition plug, which they located in a different place than the original one. The bracket at the firewall was relatively easy: just a two inch hole in the center and two 5/16 holes on either side. The under-dash bracket was a bit more trouble: I had to cut a notch for the ignition plug and add a ½ inch spacer to the right side (the two mounting holes are not directly across from each other, and the right side is a half-inch higher than the left side). Next I placed the column in place and marked where the brackets needed to be welded to the column. I found that the ignition switch interfered with the mount for the column, so I had to move the whole column forward a total of over 3 inches. This worked out fine, giving more room for me behind the wheel. I bolted the new brackets in place and tack-welded them, then removed the column and finish welded both of them.

I found that, mostly since I had to move the column in farther than planned, there was not enough room for both U-joints. Some consider it not a good practice, but the ¾ DD-shaft fits snugly inside of the one-inch column DD-shaft, so I used only the U-joint that fits onto the steering box and fastened the other end to a piece of ¾ inch DD-shaft and slid that inside of the column DD-shaft. Since both shafts need to line up in order to connect (since I used only one U-joint), and I could not push the steering wheel end of the column up all the way up to the dash until it was all the way forward, the two shafts would not line up. I ended up cutting off most of the extending part of the one-inch column DD-shaft so the ¾ shaft could be pushed far enough in so I could bolt up the steering column in place and still have room to slide the U-joint onto the steering box. (If I were to do this again, I would get a much shorter steering column.) I also had to grind a bit on the bottom of the hole in the firewall where the column went through.

With the new steering column bolted up in place, and connected to the steering box, the next step was to plug in the cables to the ignition switch and the turn signal harness. But, the turn signal plugs did not fit together! I finally took the old plug off of the old steering column, pulled the connectors out of it, and swapped the wires from the new column to the old plug.

Once I had everything hooked up, time to start it – but, while there is power with the key in the “run” position, when I turned it to “start,” the motor turns but there is no “run” power to the coil. I hooked up a temporary switch to allow the motor to start in the “run” position. The next day I pulled the column and replaced the start switch with the old one from the original column, and now it is done!



Caveats

When looking for columns for this Corvette, I found that there were different lengths, from less than 28 inches to at least 33 inches. I didn’t really know which one I needed. Eventually I found an ad that said for a C3 corvette, and it was 33 inches. That is the one I bought. But once I started to mount it, I found that the length was not that critical. Even with the 33 inch length, I still needed to add a short piece of ¾ inch “DD” steel shaft between the steering column and the steering box. I realize now that a shorter column would have worked better because as mine is, there is not enough room for both U-joints, particularly since I had to move the column forward over 3 inches. As long as the outer housing of the column reaches past the firewall, it should be fine.

If you plan on making this change, be prepared for a lot of fitting, welding, and possibly wiring issues, but the end result, I think, is well worth it.



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Re: Installing a generic tilt steering column on my 75 Coupe (2/4)
 12/22/19 1:01am
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 698

Great write-up. Someone should move it into that new section for DIY info.

Did you consider just using a smaller wheel that was available on the later years when they went to the leather-wrapped wheel?

Were you able to retain the slip joint feature in the original setup? The one that allows the steering shaft to collapse in a front-end end.



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1973 L-82 4 spd

Re: Installing a generic tilt steering column on my 75 Coupe (3/4)
 12/22/19 9:28am
BillHanna
Standard Member
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Cana, VA - USA

Vette(s):
1975 Stingray 71 350 engine Flat top pistons Sniper fuel injection Hyperspark ignition Vintage Air air conditioning Borgeson power steering box


Joined: 7/3/2016
Posts: 256

73shark said:

Great write-up. Someone should move it into that new section for DIY info.

Did you consider just using a smaller wheel that was available on the later years when they went to the leather-wrapped wheel?

Were you able to retain the slip joint feature in the original setup? The one that allows the steering shaft to collapse in a front-end end.

I thought about a smaller wheel, but I think the tilt gives more room, plus I was able to move the whole wheel away from me more.
There is about 4 inches of "slip" between the steering box and the column via. the  3/4 "DD" shaft riding inside the column shaft.  But the column is not mounted to the bottom of the dash with the slip nuts as the factory had, but it is mounted solid to the firewall as the factory also was.
 Many of the GM cars that had the safer steering column also had a collar at the base of the column that would peal the column away from itself in a crash.  It seems that without this the column is still an issue in a crash.

 

 



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Re: Installing a generic tilt steering column on my 75 Coupe (4/4)
 12/24/19 11:43pm
indy99
Limited Member
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Newport, MI - USA

Vette(s):
1980 L-48 still in the middle of a frame-off.


Joined: 6/9/2005
Posts: 930

Great write up.

 



|UPDATED|12/24/2019 8:43:57 PM (AZT)|/UPDATED|


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