OliPre94 Posted April 6, 2023 Share Posted April 6, 2023 I am having issues with my 1986 Defender 90 2.5n/a with the LT77 gearbox. After approximately 15 miles of issue free driving, I struggle to get it in gear. I would be driving and suddenly I will loose drive as if its come out of gear. With the clutch pedal pressed down, I can get it in gear but on release of the pedal, it doesn't engage and I get no drive. Sometimes I can re-engage the gear after about 5 minutes of moving it into various gears and i hear a solid clunk engagement sound. If I am moving it about on the driveway or only going for a small drive around I don't see this issue. I am not sure how small or big this issue could be, the master and slave cylinder are almost new only covering about 100 miles but have been on the vehicle for about a year and a half during restoration. There appears to be a small oil leak coming from the gearbox drain plug so I am not sure if this could be a contributing factor. The flywheel has never been replaced and neither have any other gearbox/clutch components other than the master and slave cylinder. Not really sure where to start on this any help would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Diff Posted April 7, 2023 Share Posted April 7, 2023 It sounds like perhaps there is no free play at the clutch pedal/mastercylinder. This may have altered from standard when you changed the mastercylinder. The nuts on the mastercylinder pushrod are used to set up the free play and pedal height. If there is no free play, the clutch system can 'pump' up after a number of applications of the clutch, causing clutch slip. Similarly, the flexible clutch hose can deteriorate internally causing a ' one way' valve effect, holding the clutch open for a while. Regards, Diff. 1 Quote Link to comment Share on other sites More sharing options...
OliPre94 Posted April 7, 2023 Author Share Posted April 7, 2023 5 hours ago, Diff said: It sounds like perhaps there is no free play at the clutch pedal/mastercylinder. This may have altered from standard when you changed the mastercylinder. The nuts on the mastercylinder pushrod are used to set up the free play and pedal height. If there is no free play, the clutch system can 'pump' up after a number of applications of the clutch, causing clutch slip. Similarly, the flexible clutch hose can deteriorate internally causing a ' one way' valve effect, holding the clutch open for a while. Regards, Diff. That's reassuring I do hope it's only that! The clutch pedal is adjusted so that the biting point is quite near the top of the pedal to allow for full stroke within the master cylinder currently. Sounds like I need to adjust the freeplay which would bring the pedal itself down. Quote Link to comment Share on other sites More sharing options...
Junglie Posted April 8, 2023 Share Posted April 8, 2023 It was happening with mine when I got it - adjusted the clutch free play and preoblem solved. Took 15 minutes... Quote Link to comment Share on other sites More sharing options...
pete3000 Posted April 8, 2023 Share Posted April 8, 2023 I'd be tempted to say a sticking clutch release bearing or clutch fork. Is this something that's gradually got worse? The cheaper clutch release bearings are plastic and have a tendancy to melt if the bearing gets warm. See threads around the clutch fork punching through. It worth checking the master slave first though as others have said. Quote Link to comment Share on other sites More sharing options...
Snagger Posted April 8, 2023 Share Posted April 8, 2023 I too suspect the master cylinder rod adjustment - there has to be play to ensure the master fully resets and allows the fluid back to the reservoir. Any trapped pressure will worsen with warming and thermal expansion and could be enough to slip the clutch even without applying the pedal, but can certainly cause trapping after a pedal push. Fluid draining from the bell housing can be gear oil, engine oil, clutch fluid from a slave leak or just condensation mixed with dirt. Try to get some on a clean finger and smell it, discern the colour and how thin or slippery it is. Quote Link to comment Share on other sites More sharing options...
OliPre94 Posted April 13, 2023 Author Share Posted April 13, 2023 Thank you all for your replies. I did try adjusting the clutch height and freeplay and it definitely feels a lot better. Unfortunately there is a however, I took it for the same 15 mile drive and the same thing happened in exactly the same place. I adjusted the clutch height so from the bottom it was 140mm from the floor and adjusted the rod so there was 6mm of freeplay before you felt pressure. Now I could have quite easily messed up the freeplay adjustment which would explain why it's not working. I was adjusting the freeplay from the bottom of the pedal so I was feeling resistance around 134mm from the floor. Should I have taken this measurement from the rod itself rather than the pedal? Quote Link to comment Share on other sites More sharing options...
steve b Posted April 13, 2023 Share Posted April 13, 2023 When the peal is at rest the pushrod should have approx2mm of free play between the ball end and the piston cup. Steve 1 Quote Link to comment Share on other sites More sharing options...
OliPre94 Posted April 14, 2023 Author Share Posted April 14, 2023 Tried re-adjusting the clutch pedal again yesterday as after a second thought I was sure I had made a mistake. I took it for another drive and again broke down in almost exactly the same spot and it would not go into gear. After about 10 minutes got it back in gear and 200m further up the road the same again. Either I keep getting this adjustment wrong or there is something going on inside the gearbox causing me issues Quote Link to comment Share on other sites More sharing options...
ped Posted April 14, 2023 Share Posted April 14, 2023 i had a dragging clutch on my 110 it had the same symptons as the fork tearing out at the pivot or not enough travel on the slave rodbut i knew this wasn't the cause as i always weld up the fork what it was when i seperated the box from the engine was the two followers that are on the fork and push on the release bearing had dropped off so i was getting 1/4" less travel on the release bearing Quote Link to comment Share on other sites More sharing options...
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