parsons gearbox problems

[martin cairns]

hi all, I have a parsons gearbox which I think is a HG4 , and ford 4d engine, today I was out on it and suddenly would not go into forward gear but reverse is fine, there is no noises at all, just doesn't go into forward gear,oil level is ok,filter is ok. I cant seem to find any service manuals online either. any help at all would be much appreciated, thank you

Edited May 8, 2016 by martin cairns

[RLWP]

Can you post a picture of the gearbox?

 

Richard

[martin cairns]

Can you post a picture of the gearbox?

 

Richard

hi, that's what im trying to do now, I cant seem to find a upload icon, any ideas, cheers

[RLWP]

Yes, on a PC using the full editor there is an attach file bit at the bottom

 

Richard

[martin cairns]

Yes, on a PC using the full editor there is an attach file bit at the bottom

 

Richard

[RLWP]

That does indeed seem to match the one on the Parsons Mathway website:

 

 

I haven't been in one of those - yet

 

Richard

 

MORE: As you have all the bolts out, let's have a picture of the insides

Edited May 8, 2016 by RLWP

[martin cairns]

 

Yes, on a PC using the full editor there is an attach file bit at the bottom

 

Richard

 

[RLWP]

OK, fairly typical Parsons box with a bevel gear reverse cluster. Judging by the pipes, there are two plate clutches in that central block

 

Richard

 

MORE: Parsons Mathway have a manual for it. Last time I spoke with them they were planning to get common spares made including clutch plates http://www.parsonsmathwaymarine.co.uk/manuals.htm

Edited May 8, 2016 by RLWP

[martin cairns]

 

 

Yes, on a PC using the full editor there is an attach file bit at the bottom

 

Richard

 

 

thanks for that, I shall get a manual of them tomorrow. just of your experience what do you think the problem is,cheers

[RLWP]

What's that gobby mess on the thing on the underside of the lid? There seems to have been some remedial welding

 

Oil level is OK, you can get neutral and reverse. If this is so, most of the box is working, so either you are not telling the box to go into forward or forward has failed

 

Try operating the lever on the top without the cable attached. This will tell you if the Morse control is properly adjusted

 

If that still doesn't work, I would like to know what that weld is doing

 

If that is OK, something more serious has happened

 

Richard

[martin cairns]

hi, today is the first time I have opened it up and I noticed that welding. but don't know any history of the box, the first thing I done was to disconnect the cable and manualy shift it but still failed in forward gear. neutral and reverse works fine.its been working fine until today. I have done aprox 30 hours , thanks

[RLWP]

Keeping it simple, a hydraulic gearbox has two options. The hydraulic pump either pull the forward clutch out of gear (Listers for example) or lock the forward clutch into gear (most boxes).

 

If you get neutral and reverse, the pump is working. So either it isn't being told to engage forward, or something to do with forward isn't working

 

It looks like there is a big piston in the top cover that pushes a lever down to engage the brake band for reverse. So the copper pipes are for the oil from the pump and to the forward clutch. Are these pipes loose?

 

Check that

[martin cairns]

yes I checked them pipes and are tight.

[RLWP]

yes I checked them pipes and are tight.

 

So, either the lever isn't telling the gearbox to go into forward, oil isn't getting to the clutch piston, or the clutch has failed

 

I am not clear how the valve works on this box which is why I highlighted the gob of weld. This looks like something to do with selecting forward and reverse and the weld is unusual

 

It's unlikely that you have a blocked oilway stopping oil getting to the clutch piston, but that could cause the problem you are getting

 

Most likely is the forward clutch has packed up

 

Now, please bear in mind I'm diagnosing over the internet on a gearbox I haven't seen or heard. Even so, you are getting very close to stripping it down

 

Get the manual and see what that has to say. Maybe Parsons Mathway can give you more specific advise over the 'phone

 

Richard

[martin cairns]

thanks Richard, I shall let you know the condition of clutch tomorrow and post more pics.

[martin cairns]

in the pressure release valve there was a bit dirt stopping the bearing having a good seal causing low pressure, cleaned it out and it worked fine, after a few hours its stoped working again, now ive got the gearbox out and stripped down, im not sure how much meat is supposed to be on the clutch plates. but parsons said £50 each x 7. oooofffffff, any cheaper places ???

[RLWP]

in the pressure release valve there was a bit dirt stopping the bearing having a good seal causing low pressure, cleaned it out and it worked fine, after a few hours its stoped working again, now ive got the gearbox out and stripped down, im not sure how much meat is supposed to be on the clutch plates. but parsons said £50 each x 7. oooofffffff, any cheaper places ???

 

Can you post a picture of the plates?

 

Richard

[martin cairns]

yes I will. just charging camera up

[RLWP]

You may find they are the same as one of the other Parsons boxes

 

That price is about right for getting a short run of plates made

 

Richard

[martin cairns]

I thought £350 for plates was rather expensive

I cant seem to find any plates the same on the internet that I can compare

[RLWP]

What diameter are they?

 

Richard

[martin cairns]

168 mm , inside 89mm

[RLWP]

Give me the outside diameter of the large and small plates.

 

Richard

[martin cairns]

metal plate 130mm other plate is 168

[RLWP]

5 1/8" and 6 5/8" then

 

I have a Parsons mechanical box in store, I'll strip it and measure the plates

 

Richard