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4+3 overdrive switch

Dec 19, 2001
Canton, OH
1988 Flame red coupe 4+3
OK, I've "lurked" long enough. Been reading posts for a couple months now. What a great forum!! Bought my 1st Vette this November. Waited WAY too long( 34 years). Now I need some help. Overdrive switch does not work on my 4+3. Dealer told me this when I picked it up. Also told me they were not available thru GM any more. I've emailed a couple of the vendors in the portal project a week or ten days ago, but haven't gotten a reply yet ( OK, should've called but haven't had time) Does anyone out there know where I can pick up a switch, either new or a good used one. Any info is greatly appreciated. Want to replace it before spring arrives. Thanks, Murf.
Look up a few posts

Ken's repository of Doug Nash 4+3 info is the kind.

Have you read it yet?


Thanks for the quick replies. I read and printed out all 9 pages of Kens 4+3 info about a month ago. Service manual doesn't show switch in shift knob. I'm assuming that the switch is the one below the t rod and actuator block. You're right. Trying to find one is tough.
Sorry Len, should've read a little slower. Symptoms. Overdrive is always on. Pressing switch knob doesn't turn it off. Accidently hit knob while driving on interstate a while back and OD did turn off. Had to press switch knob about a hundred times to get it back on. Haven't tried it since. Much better off, stuck in OD than not. OD will kick out on acceleration. Seems to work ok, just can't shut it off when I want to.

I wanted to welcome you, Murf, first because you're a new member of the greatest Corvette site...and secondly, because you have an '88 with a 4+3 transmission, like me!! I haven't had a bit of trouble with mine but am always aware of the possibility so read and collect 4+3 information. I'm sure you'll find a solution here for your problem.

Lemon Peel aka Elaine
overdrive not working

murf, try taking the button out of the shifter and turn the t bar that will adjust it. many times thats all it takes. the button should sit just a little higher than the shift handle. so i would try turning the t bar so it will raise the button.
Hi Murf, if you already have, as you said, printed my pages on the DN 4+3, then you know as much as I about the subject. The only thing I can say as far as acquiring a new switch would be to check with any local dealers to see if there are any switches left over in their inventory. I think mine came from the dealer when I replaced it a few years ago.

You can also check with Paul at The Gear Zone to see if they have a switch. Their web site states that "All other hard parts always available.", so you might want to check with them.

Good luck with the transmission.
How do you take the switch button off without breaking anything?
Take a small screwdriver and gently pry the button at the front and rear. It will come right off with no problem. It just snaps onto two pins.
OK, I did that and turned the T pin to raise it up and down and it still does not come out of overdrive. Any suggestions would be appreciated. Thanks
I tried the same thing. Had to replace the switch. Adjusting the rod did not work. Try Radio Shack. Part # 275-1549a. Should be around $3 or 4. Be careful when taking it apart. You do not want to lose the spring (like I did ). No replacements are available that I know of. When you replace the switch, solder the wires on and cover the connection with hot glue, similar to old switch. This prevents movement at the connection. Good luck.

There was another thread sometime earlier that showed a replacement switch that TYCO makes for about $12.00 I used it to replace mine. It had the part number also.
Is this the switch under the center console? I just ordered one for $49. I think I may be paying a little too much!
The switch is at the base of the shifter just above the linkage. Not only must you remove the center console, you also have to remove the cover for the dash and the radio to access the screws to remove the console cover. The shift knob has to be removed also. Take the knob off, unscrew the t-rod, counting the number of turns to remove it ( important). Pry the wedge (silver colored metal tab) out and unscrew the shift knob before you can remove the console cover. The switch, spring, and wiring harness will be right there. Be careful when you remove the switch. DO NOT LOSE THE SPRING. Reassemble in reverse order. Screw the t-rod in the same # of turns it took to get it out. Good luck.


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