Right who knows about gearboxes?

[Pentoman]

Is it normal for my car to clunk loudly if I try to engage a gear without using the clutch while moving along at slow speed? I mean a big loud clunk that goes through the length of the car. In my experience normally if you do this with any other car the gear merely refuses to engage (well unless you match the revs just right). But in my Mercedes 190 which has a manual getrag gearbox there's a very loud clunk if you try this. I don't try it often as it would not be good for the car but just noticed it and thought it was wrong. It also clunks when you change gear if you aren't 300% smooth with the clutch and match the revs. It also clunks from stationary putting it into first gear, most but not all of the time. As you can imagine it's a bit tiresome. Told all the propshaft couplings are okay and some are new. Is this a gearbox problem or a diff problem or?

[Pumaracing]

Could be play in just about anything in the drivetrain but it's least likely to be gearbox or diff. There really isn't anywhere in either of those to develop a huge amount of play without their operation coming to an abrupt and painful end. I'd be looking at engine or gearbox mounts, propshaft bearings or mountings, diff mountings, rear suspension bushes and then finally gearbox or diff if nothing else materialises.

[GreenV8S]

What do you mean "without using the clutch"? Judging by your comments about the gearbox refusing to engage, and needing to get the revs exactly right, you seem to be describing a clutch-less gear change. Is that really what you mean? If so I suggest you stop worrying about whether the transmission may have a bit too much backlash and worry more about the fact you're trashing the transmission. If you have backlash in the transmission this can be shown in normal driving without abusing the transmission like this.

[stevieturbo]

Are you American ?

[ringram]

Get the car safely off the ground, then you can twist the driveshaft and look for free play in it and the diff etc.
On mine the issue was cv's in the RWD half shafts

[Pentoman]

The gearbox was reconditioned 3 years ago at £400 not including the removal/fitting, but it still has a whine so didn't want to rule it out as still being a problem - but reading here it sounds like it's unlikely.

The clonk sounds like it's from further back than the gearbox. Someone else said it could be the central spline in the propshaft. There has always been a vibration at motorway speeds despite a fair few sets of tyres having been fitted, so could this too point to propshaft?

I've just been out to try things and I found that even though in daily driving it clonks when you put it in gear before pulling away, if I turn the engine off and try it there's no clonking at all.
I am confused by this as I think the engine being off shouldn't make a difference because the clutch pedal is down. Doesn't the clutch completely separate diff, prop and gearbox from the engine's turning force? Is it possible some torque still transfers through to the drivetrain, making a clonk as a worn propshaft takes up slack?



I had it in the air a while ago and there was about 1/2 inch play at the input to the diff which I heard wasn't too bad for an old car. Everything else seemed visually okay but haven't thought of the halfshafts.

Thanks.

[GreenV8S]

Pentoman said:

Is it possible some torque still transfers through to the drivetrain, making a clonk as a worn propshaft takes up slack?

It's more or less inevitable.