TR6 Replacing seals on selector shaft '74 Tr6

[Wike]

I suspect the small sealing rings located on the selector shafts in the gearbox are leaking. I was about to install a new plastic gearbox cover when I noticed some oil. The only place I can see where it might leak is under the gearshift lever where these three rings are located. I have removed the top cover from the gearbox but cannot seem to find the slots in the screwed plugs to apparently release the selector shafts. Has anyone ever changed these rings?

 

[TR3driver]

You're talking about the plugs that hold the detent springs & balls in place, correct? On the later top covers, they are pressed in rather than screwed.

Sorry I don't recall the size offhand, but I was able to find a tap (probably a bottoming tap) that would bite into the plug without having to drill. Then I slid a short length of tubing, slightly larger than the outside diameter of the plug, over the tap, and turned a nut down the tap to pull the plug out.

The plugs were in good enough condition to reuse, but I tapped for the earlier screw-in plugs anyway. TRF has both styles listed as available (108166 screwed, 156665 pressed).

On the shaft seals, I found that replacement seals (which appear to be common O-rings) did not fit snugly in the cavity. So I bought some "quad seal" O-rings, plus "split backup rings" from MMC instead:
https://www.mcmaster.com/#o-rings/=ebd2uu
The backup ring helps fill the cavity, so the cover puts some pressure on the O-ring instead of it moving around in the cavity.

Be sure to get the interlock parts back in place properly. It's easy for one of the balls to fall down inside the housing instead of staying in the bore where it belongs. If that happens, the cover may appear to work at first, but eventually the rod will come out of the center shaft and tear up the housing. Plus sooner or later you'll wind up in two gears at the same time, which is not good.

 

[Wike]

Many thanks to Randall....I was able to get the 'push-in' plugs removed. Now I am unsure how to remove the interlock parts between the shafts. Where can they be seen and how the devil do you get them out? Also, when I removed the plugs, there seemed to be a watery greasey liquid on the springs and in the bore wher the springs and balls came out of. Is this common?

 

[TR3driver]

Dang, it's been too long, I don't recall the exact sequence I used, except it wasn't quite the same as the one in the book. But basically you have to remove the pegs that hold the shift forks to the shafts (which is an adventure in itself). On early boxes you also remove the pegs that serve as stops, but I'm pretty sure yours will have the stop tubes instead (which you might want to mark).

Then I think I pulled out both side shafts (1-2 & R) before the center one (3-4). The peg should come out still in its hole in the 3-4 shaft, while the balls will probably fall out and rattle around inside the cover. Turn it up and shake until they both come out.

The pegs will likely be stuck, and the later ones twist off very easily because of the nylon insert in the side. I found an 8-point socket that would fit them (5/16 IIRC) and used a "tee" handle to turn it so I could apply force on both sides. (Using a ratchet or similar applies a bunch of side force that makes the pegs more apt to break.)
https://www.sears.com/shc/s/p_10153_12605_00904428000P?prdNo=14&blockNo=14&blockType=G14

 

[Wike]

how do I remove and replace the interlock ball and interlock small pin that is located between the three selector shafts. If you look at the TR6 Assembly Manual, Volume 1, pg 78-Plate CL, Gearbox housing and top cover detail, I'm referring to the parts labeled CL49, CL50, CL50. How do you remove and replace?
TR6 Manual on TRF site.

 

[TR3driver]

That's what I thought you were talking about. The interlock parts (two balls, CL50 and a pin CL49) are trapped in place by the shift rails (CL33, CL34, CL37). So as you remove each side rail, that will free up the ball on that side. Then the pin will come out with the center rail.

To assemble, you smear some heavy grease on the pin, push it into the center rail and install the rail in the top cover, being sure to thread it through the correct fork & spacer (CL39, CL42). No sense inserted the peg (CL44) just yet, as you'll likely need to do it again Position the rail in neutral (this might be a good time to install the detent, to hold it in neutral during the rest of the assembly).

Then what works for me is to hold the cover up on it's side, and carefully roll the interlock ball down the bore until it drops into place in its counterbore. While still holding the cover sideways (so gravity holds the ball in place), insert the shift rail for that side. Once the rail is past the ball (so the ball can't come out), you can thread the spacer & fork onto the shaft (CL40/43 or CL41/38). Position that rail in neutral as well.

Turn it up on the other side and repeat. The second side is harder, because the ball likely won't drop all the way into its bore (held up by the pin, which was pushed sideways when you installed the other side rail). Hopefully the slight taper on the end of the shaft will push the ball down into the counterbore (which in turn pushes the pin partly through the center rail and the other ball out into the interlock notch in the other side rail.

Insert the pegs into the shift forks, and then test that the interlock is working. With any rail not in neutral, both other rails should refuse to move.

 

[Wike]

Thanks for all of the info.....when I find some free time this week, I will attempt to complete this part of the journey. I really love this forum man!