403 rear Suspension

[Don Griffiths]

Want to top up the oil in the rear units, is the filler plug the very large bolt and if so any tips as to how to undo as it is very tight. Intend putting Penrite Steering Box Lub in if I ever find my way in.

[Daniel]

Hi Don,
You need to be careful with this one because no dirt at all must get inside the unit when you undo the top nut and that nut which is the filler cap is some light alloy and all 4 of them on my 400 were oxidised and hard to shift-you have to do the front ones too- the light alloy was easy to burr so apply wd40 and give it lots of time to work and use the right socket or a ring spanner-can’t remember size but can check tomorrow if no one posts it in meantime. Next time it’s an easy job and probably best to check levels twice a year because they can leak.
Finally Millers Oils do a ‘shock absorber oil light’ which is the right viscosity. You need to leave a small air gap between the oil level and the bottom of filler neck- best check manual for correct advice but from memory 1/4”
Stay safe (and sane)
Daniel

[Geoff Dowdle]

Don
Daniel's post refers to the 400 suspension units that have shock absorbers incorporated in them . They just need to be filled to the correct level with Shock oil and check regularly as the seals often leak.

The 403 use the same alloy body as the 400 and the Penrite steering box lube can be used but its very difficult to fill as it does not really flow.
I suggest you remove one of the large plugs on the side of the unit and clean the unit out the best you can . You will need the correct ring spanner to undo the plug. I found that using a large "G" clamp to hold the ring spanner on to the large plug stops the ring spanner from slipping off and damaging the plug. They are very tight !!!
To fill with the steering box lube, as Daniel mentioned make sure you clean the outside of the body thoroughly , then using a large oil syringe force the lube through the small plug on the outside of the body , that is after removing the filler plug at the top to allow the air to escape.

If they continue to leak they will require removal from the chassis and a complete strip down with new seals and probably bearings. But worth a try first .

Geoff

[Don Griffiths]

Thanks Geoff and Daniel very useful.
I think my best plan is to find a suitable socket or ring key (mine are just too small) soak with WD40 and then carefully try and free the thread, meanwhile while it's on the jack will check rear axle level (which I do quite often anyway).
Wish me luck and thanks again.

Don

[Giles]

from recollection, it might be 3/8 bsf head and so take an 18mm spanner quite well - The Classic Mechanic: MM, AF, BSW, BSF Spanner Conversion Chart

however, be careful, because the plug you are trying to undo is aluminium and very easy to damage. before realising this, I tried to undo mine with an impact wrench, and ended up having to take off the whole unit...

[Daniel]

Always bearing in mind my car is a 400 not 403, the caps on my car’s dampers fitted an 11/16 AF socket snugly- which is obviously wrong but worked!

[Don Griffiths]

Decided not to remove large plugs to clean out unit but made do with removing the top plug (no problem) and filling with Steering box lub, using a hair dryer to make the oil run easier. Thanks everyone for your advice, looking forward to getting back on the road when normality returns.

Don