Guys, be careful to stay within the rules for shifter mods:



The is no specific provision for aftermarket shift knobs as well. They could easily change the height & throw of the shifter, and be explicitly illegal. Any aftermarket component here could open you to a protest, so be sure to have your ducks in a row!

OK, let me understand this. The only way to change the throw of the shifter is to change the length of the arms at the trans, assuming that the shift lever itself remains stock at the front. That means that changing the shift rod attachment to a heim joint and bolt arrangement would NOT be a problem as long as the attachment point to the shift lever remains the same.

Is that correct?

I assume that changing the attachment stuff at the trans could be changed to heim joints as well, to remove the "footballing" of the shaft and ovaling of the opening, as long as the length is EXACTLY the same as stock as this would only remove the slop that can occur over time.

Is there really any issue with after market shift knobs??????? Why would anyone care if someone wants to put one on?

Jim

Thanks for the heads up but the length of the shift lever has not changed from stock.



And the only way to change the distance of throw is to move this pin



up or down on the shift lever. When I repair the pin, I will be sure to install the new one in the same place.

As far as overall combined height (shift lever and shift knob) they are the same too.

BIg Dog,

The way the rule is written there is no definition of "modify" other than it does not say "replace" So, it would seem you could modify the existing parts to incorporate heim joint if the measurements/geometry are kept stock.

My point was, if you do this, be prepared to show how your modification has the same geometry as the stock unit.

The OEM shift knob sits up on top of the shift lever a ways, and aftermarket shift knobs could result in a shorter total lever length.

As a racer, I don't care about your shift knob. As an official, I don't want to have to rule on this, if a protest is raised. I've seen technically valid, but petty protests like this happen in other classes, and it puts the official in a difficult situation. So my point is, just make sure you have your case for how your mod meets the definition of the rule (in this and all "mods").

As a practical point, a heim joint up front adds a degree of freedom in rotation that would cause the shift linkage to work much like a "footballed" shift lever, I would think?

Edit:

Ken, you snuck that post in while I was typing. It looks like you are good. The last sentence in your post is key - the overall height of the shift lever including the knob, is the same as stock.


BTW, Nick confirmed the 22nd was the date he can come up for the build party. My friend and mechanic Jim Hartman can make it that day as well. Nick's very confident we can get the motor in, in one evening. So it'll be Go-Carts in the morning, and engine build in the afternoon/evening!

Eric, interesting point about the heim joint as it allows for rotation without wear. I have not thought about the shifting motion and its affect on the shift rod and trans linkage at the back. I guess I always assumed the shifting was done by the position of the shift lever and that the twisting motion was the reason the shaft tended to "football", and create slop but was not important to shifting. However, you may be correct about the movement of the shift lever forcing a twist to the rod that causes the linkage at the trans to move to change gears.

I guess I had better go and actually study how the trans shifts before proposing solutions to the issue. In my case, my shift rods have always been in good shape so I just replaced the lever and problem solved.

Jim

Twist motion required. Forces the shift shaft in and out of the trans case which engages one of the (three) internal shift rods.