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Advice Wanted Re No Drive


Adrian

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one of our cars is a 1979 mgbgt.

we had what we thought was a knackered clutch, lack of drive and noise from the clutch area. so engine out, new clutch kit and release bearing in. ... the bearing was knackered, clutch looked ok.

now we have no drive at all, it is making a nasty noise which we are struggling to locate, the clutch has been fitted correctly, in fact has been in and out three times and two different clutchs fitted just to make sure the first wasnt a duff one.

it is the right clucth, right bearing, and yes fitted the right way around. hydraulics are all fine

we can engage gear fine, just when you try to accelerate the engine revs go up but seems lack of drive to wheels.

we know its not the clutch.

 

could there be a seperate fault in the gearbox or overdrive? if what any ideas.

 

any ideas plse... have tried the mg forum to no avail,, so thought i would ask you knowledgable chaps .

my son and i have been driven to drink over this!

thanks in advance

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Ok so first thing to note is a clutch the wrong way round usually means it will not release so you have constant drive.

No drive happens in all gears and reverse?

Start the car, put it in gear and attempt to drive off. What turns. Engine of course. Can you peep in the release arm hole to see the flywheel and clutch turning? Does the prop turn? Jack up the rear and lightly apply the handbrake. Does one wheel turn?

Crudely you need to decide where the disconnect is. If the clutch is OK then it needs to be a matched spline to turn the first motion shaft of the gearbox. If its turning but the prop isn't then either you are not actually selecting gears even though you think you are or the drive cannot get through the box. Input or first motion shaft if snapped would probably be obvious and it might even fall out. First motion gears are in constant mesh and transfer the drive from first motion shaft to the layshaft. Layshaft cluster then transfers the motion back to the output shaft etc. The break could be anywhere and could be noisy but basically if the input shaft turns and the output doesn't then you need to look in the gearbox. If the prop is turning then the diff becomes suspect or a halfshaft in the back axle.

I'm making it up as I go along but define where the break in drive occurs and it has to be the component immediately before the stationary one. 'When you have eliminated all other causes whatever is left has to be the problem, however unlikely.'

 

Nigel

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thanks

we have put handbrake on, disconnected the slave from the clutch arm, engaged gear...1,2,3 or 4. started engine, prop shaft does turn, but cracking gratey type noise from somewhere, have been unable to trace exactly where from due to blooming noisey exhaust

if no handbrake, the car does move slowly but not in relation to revs applied.

i think engine and gearbox out again tomorrow and check everything.

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Try lying under the car with it jacked up on stands and engine off. Put it in gear and try to turn the prop by hand. One of you try to turn a rear wheel while the other lies under the car. Hold the prop still, turn one wheel, let the prop rotate and turn a wheel, try the other etc. This should help you to locate the clunk.

 

Nigel

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Guest woolly

half shaft bust.

jackup one rear wheel put it in first gear engine off. you should not beable to turn the road wheel more than a half turn. if you can't turn the wheel try the other side.

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does the prop shaft turn in realtion to gear and revs.

If it does then its not the clutch and gearbox.

im assuming the overdrive is after the gear box,therefore makes it overdrive or diff related.

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Never know i was so intelligent!!!! Well tracked down. Rimmer Bros will prob be able to get you one,,, They used to do recon units for all the j type odrive units when I used to play with Triumphs.

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the bearing itself that failed is £89......tracked down a gearbox and overdrive from chap in derbyshire for £100,,... with warranty...... no contest.

on searching throught the debris i came across a split pin, no idea how that got inside but it appears to be the culprit. anyway back on the road again and son very happy.

thanks to all

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