gloide69 Posted December 8, 2020 Report Share Posted December 8, 2020 Hi I'm on to replacing the gearbox selector shaft O rings (a bit of a rest from body work). I made sure I was careful and not mixed up the various parts, bagging them as they were removed. All was going well, putting it back together, until setting the pull force on the reverse detent. With the retaining plug screwed flush with the casing, far too much force is require to move the reverse selector. I took the plunger out and examined it, and noticed that is different to the 3/4 plunger, with a flat (see picture) instead of being pointed. My gearbox is stamped CT22645, so I think the 3/4 and reverse plunger should be the same part? As a test, I tried the 3/4 plunger on the reverse selector and it performed OK, force required as in the manual. I guess the simple answer is to replace this part, but I'm wondering why it was in there? Thanks Paul Quote Link to post Share on other sites
Willie Posted December 10, 2020 Report Share Posted December 10, 2020 Someone might correct me, but I think it is worn. See shot of mine comparing worn to new unit! Willie Quote Link to post Share on other sites
RogerH Posted December 10, 2020 Report Share Posted December 10, 2020 Hi Willie, that does look worn. What is the selector rod like where the plunger fits. Here is a Moss new one https://www.moss-europe.co.uk/plunger-reverse-detent-106481.html?assoc=114599 Another question ??? why are there balls for the forward selectors and a cone for the reverse? Roger Quote Link to post Share on other sites
stillp Posted December 10, 2020 Report Share Posted December 10, 2020 2 hours ago, Willie said: Someone might correct me, but I think it is worn. See shot of mine comparing worn to new unit! Willie That doesn't look like wear to me - aren't there machining marks visible on the flat face? Pete Quote Link to post Share on other sites
gloide69 Posted December 10, 2020 Author Report Share Posted December 10, 2020 (edited) I was using the Buckeye Triumphs Gearbox "Top Cover Overhaul" as a reference during my strip down and I noticed that the picture for the TR6 top cover detents, has the same profile, I therefore assumed that this plunger is a TR6 item. I also spotted that in the Moss catalogue the TR4 reverse plunger is part number 106481, but for the TR6 it's 136990. (Unfortunately there isn't a picture for this one). This made me think maybe someone has fitted the wrong part, but I guess it could still just be wear? Cheers Paul Edited December 10, 2020 by gloide69 Quote Link to post Share on other sites
John Morrison Posted December 10, 2020 Report Share Posted December 10, 2020 Hi Paul, This is a photo I took of mine when doing teh top end, plunger looks the same as yours? John. Quote Link to post Share on other sites
boxofbits Posted December 10, 2020 Report Share Posted December 10, 2020 As far as I am aware the ball was superseded by the cone on later boxes. My TR4a had cones on all three selector shafts. Kevin Quote Link to post Share on other sites
Lebro Posted December 10, 2020 Report Share Posted December 10, 2020 6 hours ago, stillp said: That doesn't look like wear to me - aren't there machining marks visible on the flat face? Pete +1 doesn't look worn to me either. Bob. Quote Link to post Share on other sites
gloide69 Posted December 10, 2020 Author Report Share Posted December 10, 2020 8 hours ago, John Morrison said: Hi Paul, This is a photo I took of mine when doing teh top end, plunger looks the same as yours? John. Hi John Yes my parts are identical to yours, did you find any difficulty selecting reverse? Maybe I'll leave mine as it is and see what its like with the lever fitted. Cheers Paul Quote Link to post Share on other sites
John Morrison Posted December 10, 2020 Report Share Posted December 10, 2020 hi Paul no issues at all. Hope yours pans out OK. John. Quote Link to post Share on other sites
Willie Posted December 11, 2020 Report Share Posted December 11, 2020 My shot was taken 2 yrs ago. Gearbox and top cover overhaul. I supplied the bits for a mechanic pal to do the tech bits. One issue did arise post work - it floats out of third on overrun just now and again, some days just once. Never under load. Quote Link to post Share on other sites
MichaelH Posted December 11, 2020 Report Share Posted December 11, 2020 I had third gear falling out on the overrun: cured by checking the pressure needed to pull the selector across the dedent + spring I screwed the top screw down until I got the right release pressure . These are quite high 1/2 gear 32-34 lbs, 3/4 26-28lbs reverse 26-28 lbs measured with a spring balance. (all neatly documented in the Workshop manual) I had previously just put the springs and ball etc in so they were flat - adjusting the release loads transformed the Falling out of third gear problem I am amazed how much I learn when I go back to the Work shop manual As the saying goes RTFM Regards Michael Quote Link to post Share on other sites
gloide69 Posted January 5, 2021 Author Report Share Posted January 5, 2021 Just a little extra bit of information to answer Rogers question The profile of the notch in the selector shafts matches that of the detent plungers. I thinks this confirms that the parts are correct and matched. I've put the reverse plunger back as it came apart and when the lever is fitted, it's a bit clunky compared to 3/4, but not too difficult to to select reverse Thanks Paul Quote Link to post Share on other sites
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