Jump to content

Locked differental


Don Johnson
 Share

Recommended Posts

I am unable to lock my front differential using the push-pull knob on the floor and the indicator light below the instrument cluster does not work.

Where should i start looking for the problem?

There is no front diff-lock only the inter-axle diff-lock. I assume this is what you mean and that you have physically checked the the diff-lock is not engaging so I'll skip that bit.

On your vehicle (a 1975?) you have a vacuum actuated diff-lock - a pipe from the engine to the knob (switch valve) you mention and a pair of pipes running down to an push/pull actuator bellows on the transfer box - vacuum on one side of the diaphram engages, vacuum on the other disengages. These have a nasy habit of leaking.

Initially check all the pipes are on - they don't usually come off or break but check anyway.

My approach would be to hop underneath and swap the pipes on the actuator (on the side of the transferbox/diff output housing). If it still doesn't engage (you've swapped the pipes so engaged will be knob down) check the pipes to the actuator have reasonable vacuum - finger over the end is good enough - with no hissing noises anywhere else. No vacuum on either pipe means check further up. If the actuator is hissing when connected chances are the diaphram has broken and the unit needs replacement (about £40). It is a bit of a pain to remove due to access beside the chassis rail but is not too involved. The switches can also leak - if the vacuum is weak at the actuator check for hissing at the switch - if there is they're about £30 to replace unless it's a pipe off but you checked that first didn't you? :)

The diff-lock lock will not illuminate until the diff-lock has engaged so fixing one problem should fix the other.

AndyG

Link to comment
Share on other sites

  • 4 weeks later...

Also check the lamp in the indicator !

Caber :o

There is no front diff-lock only the inter-axle diff-lock. I assume this is what you mean and that you have physically checked the the diff-lock is not engaging so I'll skip that bit.

On your vehicle (a 1975?) you have a vacuum actuated diff-lock - a pipe from the engine to the knob (switch valve) you mention and a pair of pipes running down to an push/pull actuator bellows on the transfer box - vacuum on one side of the diaphram engages, vacuum on the other disengages. These have a nasy habit of leaking.

Initially check all the pipes are on - they don't usually come off or break but check anyway.

My approach would be to hop underneath and swap the pipes on the actuator (on the side of the transferbox/diff output housing). If it still doesn't engage (you've swapped the pipes so engaged will be knob down) check the pipes to the actuator have reasonable vacuum - finger over the end is good enough - with no hissing noises anywhere else. No vacuum on either pipe means check further up. If the actuator is hissing when connected chances are the diaphram has broken and the unit needs replacement (about £40). It is a bit of a pain to remove due to access beside the chassis rail but is not too involved. The switches can also leak - if the vacuum is weak at the actuator check for hissing at the switch - if there is they're about £30 to replace unless it's a pipe off but you checked that first didn't you? :)

The diff-lock lock will not illuminate until the diff-lock has engaged so fixing one problem should fix the other.

AndyG

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy