Diff lock-up problem

[old-git]

My Robin Hood kit car is fitted with a Sierra 7" diff and rear axle. It has developed a strange fault.

Occasionally, when reversing it will will lock up stopping the car dead. You can then move another few feet before it will do it again. Other times I can reverse with no problem.

Any ideas?

 

[HDi fun]

Not dry - no sign of oil loss?

 

[lutonmatt]

not the brake shoes moving and locking up
always used to do that

 

[old-git]

not the brake shoes moving and locking up
always used to do that

I hadn't thought of that. Why would that happen?

 

[old-git]

Not dry - no sign of oil loss?

No, checked that.

 

[turbonutter69]

My Rover Ti did this and unfortunately it was the Diff that had packed up.
Can't you remove the back plate (can't remember it's name) and take a look whilst it's moving?

 

[old-git]

It does feel more like a solid lockup rather than a shoe moving. Not an easy job to do in-situ as the rear plate also bolts to the diff mounting :-(

I think I need to take the drums off to check shoes haven't moved. If they haven't it must be the diff (can't seeing it being the gearbox as it does it in neutral).

 

[turbonutter69]

Yeah when my Rover went it wouldn't move in neutral either.

 

[jarrus]

Could it be worn plates or barings?

 

[old-git]

I don't know. It is fine in all forward gears and doesn't do it every time I reverse. But when it does it is instant, like jamming a spanner in the cogs.

 

[turbonutter69]

Hmm could well be a worn bearing then.

 

[old-git]

I'm struggling to see how a worn bearing would allow normal use in forward gears but occassional lock-ups in reverse. Surely it would cause a lockup in both directions? Also, wouldn't a worn bearing make a noise?

 

[turbonutter69]

I'm struggling to see how a worn bearing would allow normal use in forward gears but occassional lock-ups in reverse. Surely it would cause a lockup in both directions? Also, wouldn't a worn bearing make a noise?

You would of thought so yes.
My thought is a bearing could be damaged in some way and when you move it in reverse something is getting lodged. Which would lock it up. See where i'm coming from?
Is this on the Cossie box?

 

[old-git]

No, it's a 4 speed ford box.

 

[turbonutter69]

Ok so there would be no chance mistakenly putting it in reverse instead of a forwards gear?
Was going to say someone could of grinded reverse by accident whilst going forwards.

 

[old-git]

Not gearbox as it does it even if pushing car in neutral.

 

[HDi fun]

Not gearbox as it does it even if pushing car in neutral.

In neutral the diff is still connected to the gearbox output shaft.

 

[old-git]

True, But I am pretty sure it isn't the box.

 

[HDi fun]

This is a strange one, to say the very least. I agree that if it were 'box related then surely some symptoms would show here and there in general driving.

Perhaps 'dismantling the diff time' is drawing closer.

 

[old-git]

Unfortunately, you are correct. Not knowing what the problem is is worrying. I can't be sure it won't happen in a forward gear and this would spoil my day. It is due for an MOT and the weather is improving so I am going to have to get dirty.

 

[HDi fun]

If it locked up when you're taking a bend or corner it would very much spoil your day I expect.

Diffs are very sensitive to correct torqueing during assembly or re-assembly. They can also be touchy about oils. EP oils can cause all sorts of problems if a 75w/90 (non EP) is specified, for example.

 

[turbonutter69]

From my experience with my Ti it does sound like it's a diff problem. You are going to have to get your hands dirty my friend.

 

[lutonmatt]

sorry forgot about this one og
some cars used to do it all the time more the ford axles and french stuff
dont ask me why it does it but normaly a set of shoes and new drums help

my trans am does it all the time could drive all day ok i reverse it in the garage and it will lock up passager side my old 79 did it as well
think it could be a driving alxe with drums thats the proplem