Technical What mistake have I made?

[chrisparr]

Hello all.

My Fiat 500 1.2 petrol manual is in bits on my driveway. Bought it with a lot of damage for next to nothing as a project.

The subframe is off to replace the gearbox and I’ve also replaced the clutch. Now, after I’ve refitted the gearbox, I can turn the hub with the car in gear, but as it turns, the engine doesn’t turn with it. The other hub does turn so in my head that says the gearbox is operating correctly. As the car is in gear, I would have expected the engine to turn as I turn the hub.

The gearbox was a right pain to locate back in position, so before I take it off again, is there something obvious I could be missing?

I’m pretty positive I fitted the clutch plate the correct way round as I remember double checking. I can also see the gear linkages move as I change gears.

Annoyingly I can’t simply start the car and see if I have drive as it also has an electrical problem at the moment I also need to fix (I love me a project).

Any suggestions would be helpful. All I can think of is I actually did put the clutch plate in the wrong way round even though I’m positive I didn’t.

Also hints and tips for easily handling and locating the gearbox when the car is on axel stands would also be welcome.

Thanks in advance.

 

[chrisparr]

On reflection, what I didn’t do was put the clutch plate over the splines on the gearbox first to check it mated properly

I trusted euro car parts to give me the correct clutch kit. I wonder if that is the problem.

 

[The Panda Nut]

DAFT QUESTION BUT IS IT IN GEAR.

Try getting someone to turn the other wheel at the same time.

Turn the engine (in gear) and see if wheels turn. One will turn but not often both.
Im sure you would have noticed a wrong clutch.

 

[ZaphodB]

Now, after I’ve refitted the gearbox, I can turn the hub with the car in gear, but as it turns, the engine doesn’t turn with it. The other hub does turn so in my head that says the gearbox is operating correctly. As the car is in gear, I would have expected the engine to turn as I turn the hub.

so before I take it off again, is there something obvious I could be missing?

If you're turning one hub the other will turn, but it won't turn the engine unless you stop that other hub turning (cos there's a diff in the way)

And once you stop that other hub turning, whether you can turn the engine over will depend on what gear it is in, (i.e. you'll do it with a higher gear)

 

[rmjbn1]

I agree with ZaphodB.

As you turn one hub, you'll notice the opposite hub rotating in the other direction.

This is transferring motion through the differential gears only, it's not transmitting drive to the gearbox.

There's an inspection window on the top of the bell-housing. You should be able to see the input shaft and clutch assembly remain stationary as you turn a hub.

 

[chrisparr]

Ah, I see.

Maybe I haven't messed up. Thanks for my gearbox/differential lesson

It's raining sideways at the moment, but once it's cleared up I'll rotate the engine and then see. I'm a fan of learning by doing. Today I have learned a bit. I do hope I haven't made a mistake and this concludes today's lesson

Thanks for all the responses.

 

[rmjbn1]

I learned how a differential works from LEGO Technic sets!

A couple of videos that explain it quite well, whilst it's raining:
From around 3:40