Fabbing Shifter Linkage

[Earley Motorsports]

Hi. I need some help here please. The shifter linkage for a Hewland MK9, what size tube does it need to be and how many universals should there be? I made one out of 1/2" 16 gauge tubing with a universal about 3" from the gearbox shift input rod, another just in front of the brake rotor to go up to another right beside the fuel pump. Then it is straight to the gear lever. I can't get it to work though. Any ideas, is my tubing too small It sure looks nice but don't work worth a crap . Any help would be greatly appreciated. Thanks.

[Steve Demeter]

How many universals depends on how contorted the path of the linkage needs to be to get around all the stuff in it's way.

Mine has exactly two and all the rods are straight.

16 gage tubing sounds a bit thin on the wall to me.

I would try to get the big rod end in the second pic lower as that piece between the two universals looks to be at one heck of a mechanical disadvantage.

[S Lathrop]

Materials: I use 5/8 dia. tubing and 5/8 Apex joints (1/2 ID). If you want to save money on u-joints, use 3/4 diameter joints. Apex will last decades, any thing cheaper will not last.

That drop to get under the brake disk and axel on your car just isn't going to work.

On the Zink Z10, the shaft through the engine compartment passed along the bottom frame rails. On the Zink Z16 I had a horizontal shaft from shift selector on the transmission to the rear bulkhead. The shaft had a dog leg to pass around rotor and below the caliper. The dog leg was made from 3/4 diameter material.

You are better off bending the shafts to minimize the angles through the u-joints. On my current shift system, I have 4 u-joints. I have less than 10 degrees between the 2 shafts through any joint.

[Will Velkoff]

It also looks like in the second picture you have the threaded portion of the linkage passing through the rod end. That's not going to work either.

[Earley Motorsports]

Thanks for the advise guys. That is what I needed to know. It looks as though it is back to the drawing board. Never mind, all learning to me. I have built just about everything on the car so what is a bit more. . Thanks again, that is why this site is such an asset to everybody, lots of great advice and experience.

[S Lathrop]

When you start, take a string and try to draw it between the transmission selector finger and the pivot for the shift lever, straight line. Or at least try to picture that line. Build your shift system as close to that line as possible. Don't be afraid to have the shaft bump around components that are in the way.

The Zink Z10 had a center shift shaft that was mounted just above the lower frame rails in the engine bay. Ed used 5/8 in. pillow blocks to mount the shaft. The shaft to the transmission ran inside the rear brake rotor. The shift lever pivot bearing mounted just under the upper frame rail about 6" rear of the dash. The shaft from the lever ran down to the shaft going through the engine bay. All the shafts were 5/8 16 ga. tubing. This system worked well, was easy to build. Getting the pillow blocks aligned was a one time issue.