Strange gearbox/clutch problem (V8/LT77)
Discussion
adam quantrill said:
Don't think so, but thanks for the ideas, keep them coming. What does work:
1. All gears will engage with the engine stopped. The car will drive too.
2. Clutch has a definite good bite point and loads of travel either side.
3. You can start it in gear with your foot on the clutch, then let foot off and the car will move.
4. No noises from release bearing.
Tending not to sound like a cluch issue then. I was thinking if the selector forks weren't secure on the shaft then as you try to pick a gear it prefers to slide the shaft through the forks than for the forks to move the synchros. With the engine stopped the synchros won't be rotating so will pop in easier.1. All gears will engage with the engine stopped. The car will drive too.
2. Clutch has a definite good bite point and loads of travel either side.
3. You can start it in gear with your foot on the clutch, then let foot off and the car will move.
4. No noises from release bearing.
I'm still thinking (hoping?) some sort of clutch fault. What doesn't work:
1. Changing out of any gear above 2500 rpm
2. Changing down from 4th to 3rd, or lower gears, unless stopped.
3. Changing from Neutral to Reverse grates (even if you select another gear first)
4. (80% of the time now) selecting any gear with the engine running - sometimes works though.
5. When depressing the clutch above 2500 rpm the engine revs don't die as they should, but below 2000 rpm they seem to die away fine.
I'll take a look at the clutch first - my suspicion is that it's dragging and spinning up the input shaft thereby defeating the syncros. If that fails to show an obvious fault then the box will have to come out.
1. Changing out of any gear above 2500 rpm
2. Changing down from 4th to 3rd, or lower gears, unless stopped.
3. Changing from Neutral to Reverse grates (even if you select another gear first)
4. (80% of the time now) selecting any gear with the engine running - sometimes works though.
5. When depressing the clutch above 2500 rpm the engine revs don't die as they should, but below 2000 rpm they seem to die away fine.
I'll take a look at the clutch first - my suspicion is that it's dragging and spinning up the input shaft thereby defeating the syncros. If that fails to show an obvious fault then the box will have to come out.
adam quantrill said:
I'll take a look at the clutch first - my suspicion is that it's dragging and spinning up the input shaft thereby defeating the syncros. If that fails to show an obvious fault then the box will have to come out.
The only way I can see that happening from your descriptions is if the friction plate is welded to the cover!Flushing the box sounds like an easy first step ..
If that does not fix it then it sounds a bit like the clutch not fully disengaging.
Which could be things like :
Too much free play at pedal
Bearing not located on arm properly (especially if its the plastic type)
Arm part broken .. punch thru on fulcrum or bent..
Problem with diaphram mechanism
If that does not fix it then it sounds a bit like the clutch not fully disengaging.
Which could be things like :
Too much free play at pedal
Bearing not located on arm properly (especially if its the plastic type)
Arm part broken .. punch thru on fulcrum or bent..
Problem with diaphram mechanism
Wedg1e said:
The only way I can see that happening from your descriptions is if the friction plate is welded to the cover!
IanI think you have hit on the problem, with his power and they way he likes to use it (sensably) its that or a broken piece of lining jaming things!
Adam I think its clutch time mate!
You have only got 54/55 days to the fest!
Andy
Mr Tank said:
Ian
I think you have hit on the problem, with his power and they way he likes to use it (sensably) its that or a broken piece of lining jaming things!
Adam I think its clutch time mate!
You have only got 54/55 days to the fest!
Andy
Could be the friction plate has over heated and is stickly on the flywheel at times.I think you have hit on the problem, with his power and they way he likes to use it (sensably) its that or a broken piece of lining jaming things!
Adam I think its clutch time mate!
You have only got 54/55 days to the fest!
Andy
Thanks, good suggestions. Well I had a poke inside the bellhousing with the endoscope, the arm and release bearing look fine, move OK, but you can't see much else.
So I have started pulling it apart - having done it once before it's a known quantity, just hope I find a clutch problem and don't have to pull out the box too.
As an aside I pulled apart a spare LT77 box that was jumping out of gear all those years ago when it was in a car, and the fault turned out to be one little bearing in the middle. The rest of it looks good so I have a box of spares (literally) apart from the input shaft that I gave to a mate.
Today I made more progress after looking at the Jeep - needs a new UJ - and am now almost at the point of splitting g/b and engine. hopefully tomorrow I will have the clutch out to give it a once over.
So I have started pulling it apart - having done it once before it's a known quantity, just hope I find a clutch problem and don't have to pull out the box too.
As an aside I pulled apart a spare LT77 box that was jumping out of gear all those years ago when it was in a car, and the fault turned out to be one little bearing in the middle. The rest of it looks good so I have a box of spares (literally) apart from the input shaft that I gave to a mate.
Today I made more progress after looking at the Jeep - needs a new UJ - and am now almost at the point of splitting g/b and engine. hopefully tomorrow I will have the clutch out to give it a once over.
Edited by adam quantrill on Sunday 6th May 19:04
At last - I think I've found the problem! ;^)
Note that three of the springs in the friction plate are busted, plus these three steel parts fell out when I freed it off - they were obviously stuck between the friction plate and cover plate with nowhere to go, so were causing the clutch to drag. Quite why it didn't make a clanking noise I don't know.
Ift also fits the symptoms very well - at high rpm the metal fragments were being thrust outwards to wedge in the friction material - in fact you can see eroded parts of the friction meterial on the inside edge, where they were bedding in. So at high rpm the clutch dragged more!
I just shook out the cover plate and found two more bits of the same metal, but otherwise it looks in good nick so will be re-used.
So - not getting a National clutch plate again, only lasted 20k miles. If I can find the old one I took out at 25k I might put it back in - at least the parts in it seems strong and it had a lot of friction material left.
Or else any recommendations for good clutch plates at a reasonable price?
Note that three of the springs in the friction plate are busted, plus these three steel parts fell out when I freed it off - they were obviously stuck between the friction plate and cover plate with nowhere to go, so were causing the clutch to drag. Quite why it didn't make a clanking noise I don't know.
Ift also fits the symptoms very well - at high rpm the metal fragments were being thrust outwards to wedge in the friction material - in fact you can see eroded parts of the friction meterial on the inside edge, where they were bedding in. So at high rpm the clutch dragged more!
I just shook out the cover plate and found two more bits of the same metal, but otherwise it looks in good nick so will be re-used.
So - not getting a National clutch plate again, only lasted 20k miles. If I can find the old one I took out at 25k I might put it back in - at least the parts in it seems strong and it had a lot of friction material left.
Or else any recommendations for good clutch plates at a reasonable price?
Edited by adam quantrill on Monday 7th May 19:45
Yes it is good news - the box input shaft feels fine and hopefully it didn't take too much stress from the crunchy gearchanges. Time will tell.
Yes you can do the clutch without removing the engine, the procedure is here:
Clutch Progress
I'll see if I can get piccies to add to it as it is split open right now so it's the ideal time.
Yes you can do the clutch without removing the engine, the procedure is here:
Clutch Progress
I'll see if I can get piccies to add to it as it is split open right now so it's the ideal time.
Well it's finally going back together - wasted a day yesterday almost getting hte box back on and it wouldn't quite go, so pulled it apart again and finally got it on today. I also put the clutch slave on temporarily to check the action and it seems fine, so it's just a case of putting all the other bits back on and we'll be mobile again.
The Beast Breathes Again
Well finished it off tonight, sorted out an intake hose, and took it for a little spin.
1. No graunching in reverse any more!
2. I can change up - whatever the revs!
3. I can change down too - whoo hoo!
I did have a small scare when I put my foot on the clutch before I got it off the axle stands and it went to the floor - I musta been tired last night and trapped the release pin behind the clutch cover, then put the clutch slave in with no pin? Or maybe it slipped out? Anyhoo it was quickly sorted and back operational again.
Zig - only one bolt left over so my tray technique works pretty well!
BBWF here we come!
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