Pollywog Posted February 16, 2014 Share Posted February 16, 2014 Hi guys, Today I went on a BORDA training course at Whitecliff in Coleford and had a great day. The only let down was the fact that every time I came to do a descent my Series 3 wanted to jump out of 1st gear so I was having to hold it in constantly. It jumps out on even the slightest downward incline under engine breaking and from the regularity of the jumps I think we've come to the conclusion that perhaps the first gear cog is missing a tooth? The box is a D suffix series 3 box, I've never had to work on the internals of a gearbox before so this is all new to me. How involved a job is changing the first gear cog? Does it mean a complete rebuild of the gear box? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
aaronledwidge Posted February 16, 2014 Share Posted February 16, 2014 Is it violent or gentle. It could be it needs new detention springs Quote Link to comment Share on other sites More sharing options...
Pollywog Posted February 16, 2014 Author Share Posted February 16, 2014 Hi, Well it feels quite violent to me, I was having to hold it quite firmly to keep it in gear. It was jumping at regular intervals almost like it was at a set number of wheel revolutions which is what made me think a missing tooth? Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 17, 2014 Share Posted February 17, 2014 The suffix D box was revised to address the earlier problems of jumping out of gear by having coffin shaped dog clutch teeth so that they actually tend to pull into gear. If your box is definitely a full Suffix D then I would first suspect that the mainshaft nut has worked loose allowing the shaft to move forward. Less likely but possible is that the 1st/2nd selector fork pinch bolt has loosened and finally from me , a small stone or similar may have become lodged between the selector shaft and the gearbox top preventing full engagement of 1st gear. Quote Link to comment Share on other sites More sharing options...
aaronledwidge Posted February 17, 2014 Share Posted February 17, 2014 Interesting that, I had a box that violently released but it was chewed teeth, my reverse had broken up. If its not gentle it won't be detent issues. Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 17, 2014 Share Posted February 17, 2014 Bill's comments are right. My money is on a loose main shaft nut inside the transfer box (the back end of the gear box's main shaft). However, a bad set of main shaft bearings or a bad 1st gear bush (worn to a taper) could have these symptoms. A mal-positioned fork on the selector shaft could be at fault - the Suffix D unit has a very specific measurement on the position of the fork pads from the rear end of the shaft, and if mis-set such problems will occur. I don't think the detents will have anything to do with it, though I have been known to be wrong... Best start with the main shaft nut and fork position and see how things go. You don't want to get inside the box unless you have to... Quote Link to comment Share on other sites More sharing options...
Pollywog Posted February 17, 2014 Author Share Posted February 17, 2014 Hi guys, Thanks very much for all your input. On my way home tonight I stopped at the top of a hill to try it in high range and it is doing the same but not so violently. I'll get the inspection plate off tomorrow and check the main nut. I'm not having any issues with the reverse gear. Quote Link to comment Share on other sites More sharing options...
Pollywog Posted February 19, 2014 Author Share Posted February 19, 2014 Nothings ever that simple is it, of course to check the main nut I'll have to remove the overdrive. Looks like that's going to have to wait a few days. Quote Link to comment Share on other sites More sharing options...
Pollywog Posted July 26, 2014 Author Share Posted July 26, 2014 Quick update, I finally got several days where I didn't need to use the car so off came the overdrive and yes indeed the main nut was loose, new nut & lock washer on and torqued up properly. Whilst I was at it I found the shim on the intermediate shaft had been chewed up so have fitted a new pair of thrust washers and shim. Good news is it's a lot quieter than it was before, bad news is it's still jumping out of gear Next up selector forks... Quote Link to comment Share on other sites More sharing options...
Snagger Posted July 30, 2014 Share Posted July 30, 2014 Check the distance between the aft face of the fork pads and the centre of the selector inhibitor pin is 18.2mm, critical on a suffix D. Quote Link to comment Share on other sites More sharing options...
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