30 clark 4 speed gears

Home Page Forums Chassis 30 clark 4 speed gears

Viewing 3 posts - 1 through 3 (of 3 total)
  • Author
  • #389910

    I am working on a project to stabilize the 3rd gear set in the 30 clark transmission. Currently the rivits that hold the gears together have had a tendency to come loose causing the teeth to chip and destroy the transmission.
    I am working on a new method to bolt the gears together so they can’t come apart. Does anyone have some old broken gear sets that I could use for testing and possible rebuild?


    Don’t throw out those gears yet, you may find it impossible to make or replace those. They are matched sets, and must be assembled with care. The gears come in sets and have an indexing mark on them. Take the old gears and grind off the edges of the chiped teeth. Reassemble with improved rivets and see if they won’t work for you. The gear teeth ‘walk’ around the two gear halves at a different rate to keep the gear noise down, and when properly assembled are remarkably quiet. There are two oppinion ‘camps’ on this transmission; one group hates this box and will try to get you to replace it with a standard 3 speed unit. Another group thinks that this was one of the finest manual boxes ever built. The average mechanic will ruin the box if not warned in advanced of its unusual design. Clark made this box for several major car companies, but Pierce had a unique design and characteristics not provided to the other companies. Call me if you need to discuss this further. Bill



    Thanks for the input. I am one of the guys that likes the transmission.

    I have several thoughts about the third gear set. I am looking at a way of bolting the gears together with 5/16×24 grade 8 bolts. With the clearance this works perfectly on the lower set. The clearance on the top set is very limited. I think flat head bolts and a lot of locktight will work fine.

    I am also wondering why they went with that set of gears when the input gear set have identical number of teeth. Why not just go with identical halves. It would make assembly a lot easier.

    To my way of thinking the 2 1/4 inch woodriff keys adsorb all the rotational forces and the rivets are just there to keep the gears together.

    Anyway I am checking with several gear manufacturers to see what it would take to have gears made. With cnc being what it is, there should be no problems in making the gears. The top and bottom sets are identical in OD and ID. The only difference is the recess for the retainer ring on the backside of the upper gear.

    If anyone is interested in have the gear sets made let me know.

Viewing 3 posts - 1 through 3 (of 3 total)
  • You must be logged in to reply to this topic.