5th Gear Lockout

Sometimes I wish I’d kept more videos, but disk space ain’t free. I could put together a pretty solid compilation all the way back to the STS days of myself and my codrivers consistently missing 3rd gear and hitting 5th on faster courses. During normal driving it was never a problem, but when exiting a corner at an autocross at the top of 2nd gear, it seems like 75% of the time it just wants to go into 5th. After it still being a problem even with delrin engine and differential bushings, and a delrin shifter bushing, I decided to do something about it.

I’ve seen a couple on other cars, and borrowed a ideas from just about all of them. I wanted something simple (ie: that I could make myself), something easily disabled (reverse is often needed for getting around paddock & grid), and fairly easily removable.

First up was figuring out where to mount it. I played around with a couple different things and settled on having it reside between the transmission tunnel and the upper dust boot, on the passenger side, and use the 2 bolts for the dust boot along that side to secure it. A length of 1.5″ steel angle made a solid base for the lockout after a little love from the angle ginder.

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A 3″ or so length of butt-hinge left over from another project gave me more than enough width to cover the full throw of the shift lever, and would allow the devise to be easily swung ‘open,’ away from the shifter.

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I didn’t want the shifter ever making metal-metal contact, so I grabbed (and then sacrificed) a cheap plastic cutting board to use as the bumper for the shifter to contact.

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With the height and positioning set, I could stitch the hinge to the base:

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So that the bumper didn’t sit too low and contact the dust boot, I added a stop to keep it in place in the closed position. In the open position, the hinge runs out of travel and naturally stops at around 90°.

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The thing was starting to get heavy, so the angle grinders and big drill bits came out to take some weight off. Here I’ve also added the spring retainers out of 1/8″ steel bar for a spring that will hold it steady at either end of its travel:

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A coat of paint to keep the rust at bay, some final finishing on the bumper piece (it’s still completely flat throughout the full throw of the shifter), and final assembly, and it should be good to go.

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I’m really happy with how it came out. It looks a lot less hacked together than a) it is, and b) I expected it to look as it was starting to come together.

Here’s a quick video made towards the end of mocking everything up, after securing the bumper in what should be its the final position. Unforunately it’s just a static test, I don’t have a way of getting the car into a position that creates the 2nd > 5th problem safely in my neighborhood, so I’m not even going to try. However, it seems to work great. There’s about 3/16″ between the shifter and its resting place in 3rd gear, and that seems to be enough to where it doesn’t try and skip 3rd and get jammed in the gate to 5th / Reverse, but also isn’t resting against the bumper. In the video, I’m also being way rougher than I ever would in reality just to make sure it doesn’t try and skip the 3rd gear gate.

 

I’m really pleased with how positive the action is, and how well it sits against the stops. I was worried I’d need to add a second spring (like in the example linked to earlier), but it’s nice and snug without being too hard to flip to the open position.

 

UPDATE!

The 1st event we ran this at resulted in nearly worse performance. After doing some testing, it became clear that it was actually guiding the shifter into hitting the stop between 3rd and 5th. To make it work, with the shifter in neutral, the lockout actually needs to push the shifter a bit towards the 1 / 2 gates. It turned out that we didn’t actually need it at our last event, however we tried it out on first runs just to see, and now it’s guiding directly into 3rd under load. Success!

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2 thoughts on “5th Gear Lockout

  1. Very nice DIY fix for an existing problem. I’m going to try using this idea as a 1-2 lock out on drag cars using a dogbox transmission. I’ll even take it a step further by making the height adjustable, as well as the distance between the stop plate and the rod, so as to guide the shift rod into 3rd, and away from the 1-2 gate. Also looking at making it a staged application, as well.
    I’d like to give you credit for the idea – do you have a name or handle that you go by?

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    • Hi Chuck! I’m Andrew Maffessanti. My ‘idea’ was an evolution on something someone did before me. Shoot me a link when you get it together. I’d love to see the next link in that evolutionary chain 🙂

      Like

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