Gearbox slipping

[midnight cowboy]

Our Blackston gearbox attached to Lister HR2 is coming out of forward gear after about 1 hour boating. Reverse OK. Locks in again when engine cools down. Then the same. Any suggestions why this is happening?

[Quattrodave]

2 hours ago, midnight cowboy said:

Locks in again when engine cools down.

 

I'm a little surprised by this sentence, are the engine and gearbox physically seperate and linked only by a a drive shaft? Or do the engine & gearbox share oil and or coolant??

 

Any photos available??

Edited October 11, 2023 by Quattrodave

[alan_fincher]

11 minutes ago, Quattrodave said:

 

I'm a little surprised by this sentence, are the engine and gearbox physically seperate and linked only by a a drive shaft? Or do the engine & gearbox share oil and or coolant??

For an HR2 coupled to a Blackstone box, the oil is shared between the  two.  It's air cooled so no coolant.

[midnight cowboy]

29 minutes ago, Quattrodave said:

 

I'm a little surprised by this sentence, are the engine and gearbox physically seperate and linked only by a a drive shaft? Or do the engine & gearbox share oil and or coolant??

 

Any photos available??

They are linked and share oil - as it is air cooled there is no coolant to share

[Tony Brooks]

Just to rule a lesser possibility out, are you using the recommended engine oil. I could imagine a modern 5W15 would play havoc in such a gearbox.

 

My guess is that it is a sun & planet wheel gearbox, but I may well be wrong. If it is then reverse is typically done with a brake band and ahead with a cone or multi-plate clutch, so if there is one it may be worth checking the ahead adjustment. This might all be cobblers, so wait for other replies from the more knowledgeable.

[midnight cowboy]

We use traditional mineral oil from Morrison

 

[Tracy D'arth]

Is this an LM100 gearbox?  Or less likely an LH150?  There are pictures on the net to identify.

 

If an LM100, see here   for help.  https://listerparts.co.uk/LM100.html

It is possibly the cone clutch need relining but check that full engagement of the lever is possible and its not just a slack linkage not allowing full travel.

[Tony Brooks]

49 minutes ago, Tracy D'arth said:

Is this an LM100 gearbox?  Or less likely an LH150?  There are pictures on the net to identify.

 

If an LM100, see here   for help.  https://listerparts.co.uk/LM100.html

It is possibly the cone clutch need relining but check that full engagement of the lever is possible and its not just a slack linkage not allowing full travel.

 

I suspect it is neither because our yard tug had an LH100 that had its own oil and dip stick, and the SL4 had LH150s, again with their own oil and dipstick.

 

1 hour ago, midnight cowboy said:

We use traditional mineral oil from Morrison

 

 

I think that you mean Morris oils, but "traditional" means nothing. What is its SAE rating and does it meet the spec recommended for your engine. My gues is that you are using SAE 30, but only you know.

[David Mack]

1 hour ago, Tracy D'arth said:

Is this an LM100 gearbox?  Or less likely an LH150?  There are pictures on the net to identify.

OP says it's a Blackston(e) box.

[midnight cowboy]

 

17 hours ago, Tracy D'arth said:

Is this an LM100 gearbox?  Or less likely an LH150?  There are pictures on the net to identify.

 

If an LM100, see here   for help.  https://listerparts.co.uk/LM100.html

It is possibly the cone clutch need relining but check that full engagement of the lever is possible and its not just a slack linkage not allowing full travel.

Ours is a Blackstone gearbox similar to LM1xx

There is no filler as the engine oil lubricates the box There are 6 bolts holding the cast aluminum cover

There is a separate 3/1 reduction box

[Tony Brooks]

That look rather like the LH100 than a Blackstone box, although it may be a bit larger. I would have the cover off to inspect the ahead engagement. The mechanism is often three or four fancy shaped bell cranks operated by a sliding cam. The fancy shape or the shape of the cam forms a sort of detent to hold it in gear, so being out of adjustment might result in it coming out of gear.

 

Note - based on typical practice, not this particular box.

[Liam]

It'll be a Lister Blackstone 2G gearbox, fitted with a 3:1 reduction in this case.

 

When engaging forward gear on mine there's a definite "snap" into ahead, so there must be some fair force at play to throw it out of gear.

[roland elsdon]

The forward throw adjuster is almost all the way out on the box in the picture. It has some travel left though so you may be able to  get the rod further in.

Also check the detent on the selector,  the neutral finding pin may be stuck. ( if its there at all?)

You might want to check the selector plate( the platewith the fore and aft adjuster screws is tight as well, they can rock .

 

If you do increase the throw on the lever you should probably lift the to off the box and adjust the clutch throw .

Never more than quarter turn  on the adjuster without checking clutch disengages though, or you can break the clutch plate.

They are pretty trouble free normally 11 years and countless miles on ours with one adjustment in that time.

[Steve56]

The gearbox you have is the Lister 2G. Here's the info for adjusting the box. May be of some help.

[midnight cowboy]

Thanks for all the replies.  We are steadily working through the various points and suggestions you all made and will post an update in due course

[Tony Brooks]

FWIW, as soon as I saw Steve56's post, my immediate thought was that the ahead adjustment so out so the "links are not going over centre".