4 speed Crash Gearbox Illustration

[Old Dave]

I do David - Often.

The Light Car illustration lacks a big chunk of swarf that must be collected on my drain plug.

I believe a magnetic plug is available though mine isn't one.

Thanks for posting the illustration Bruce    -   perhaps there should be a register for cars with 4 speed crash?? Did I read that this box is the strongest fitted to an A7?

[Chris KC]

I do David - Often.

The Light Car illustration lacks a big chunk of swarf that must be collected on my drain plug.

I believe a magnetic plug is available though mine isn't one.

Thanks for posting the illustration Bruce    -   perhaps there should be a register for cars with 4 speed crash?? Did I read that this box is the strongest fitted to an A7?

They're certainly tough, and often in good nick because people "upgraded" to synchro boxes when they started to become available in scrapyards. The downside is the gap between intermediate gears and top is even bigger than on other A7 boxes...

[David Stepney]

I've never had a problem with my gearbox. Admittedly, it wails like a demented banshee in second when pulling hard, and isn't much quieter in third. 30mph is just about manageable in third - I can't remember what the synchro box will allow - but the overall gearing is quite adequate given all the hills around here. It sound a bit 'whirry' in neutral with the engine running, which goes if one depresses the clutch, but I can't decide whether the noise is the gearbox or the engine rear main.

[Reckless Rat]

I stripped and rebuilt my 4 speed crash box a few years ago and apart from replacing the bearings and the detent balls and springs, all was in good order after 90 years.My particular car ha crossed the Alps and the Pyrenees ( several times) without problems. It's just a matter of accepting that once you've selected 3rd then that's it until you're over the crest. OK the gearbox is slow, but deal with it. I tried a 3 syn box and it was rubbish.

[David Stepney]

Don't get me wrong, Brice. I am perfectly happy with my crash box. It is, after all the one that was originally fitted to the car. After nearly 115K miles and 90 years, I suspect that it could be refreshed by fitting new bearings, but, while it is working and giving no trouble I intend to leave well alone. Besides, as I said in my previous post, the gearing is well suited to the local terrain. My original enquiry was simply to understand exactly how the gearbox worked should I ever have to work on it, something that is not apparent either from the parts list or or the section of its overhaul in Doug Woodrow's excellent book.

And, of course, it is a lovely drawing!

[Chris KC]

David StepneyDon't get me wrong, Brice. I am perfectly happy with my crash box. It is, after all the one that was originally fitted to the car. After nearly 115K miles and 90 years, I suspect that it could be refreshed by fitting new bearings, but, while it is working and giving no trouble I intend to leave well alone. Besides, as I said in my previous post, the gearing is well suited to the local terrain. My original enquiry was simply to understand exactly how the gearbox worked should I ever have to work on it, something that is not apparent either from the parts list or or the section of its overhaul in Doug Woodrow's excellent book.

And, of course, it is a lovely drawing!



Should you ever need to rebuild it David drop me a line as I have photos and some notes - though it isn't a great deal different from the other boxes in practical terms. Yes mine has an impressive howl in 2nd and I briefly get to pretend my car is supercharged!

[David Stepney]

Thank you Chris. That’s very kind of you. There are a number of jobs that I would like to do to the car but nothing pressing apart from the rear shock absorber links. One of the jobs that I really should do is to replace the rear springs as they are a bit tired and are probably the originals. At the moment, the gearbox is working as it should and I note that Doug Woodrow’s advice is to leave it alone unless urgent attention is required. One of these days though.......

[Reckless Rat]

A large beardy bloke I know has driven my car and he says it's the quietest 4 speed crash he's ever driven... (perhaps he was just being nice to me)

[Steve kay]

Still have not managed to find out how to quote or reply. If I could I would be asking M. Requelesse whether the Pyrenees and Alps are in Lincolnshire. Or maybe he ascends them in third gear with the aid of a blower, or competition cam, or a tohc conversion. Wales and the Cotswolds quite often require second, and just very occasionally, premiere gear.

[Reckless Rat]

My RP will go up most hills in 3rd, including the Alps and the Pyrenees. Occasionally if it's really steep I might have to revert to 2nd, but if that happens you're generally stuck unless you can get up enough speed to get back into 3rd. The 4 speed crash box is slow. Third gear ratio is slightly lower than 3rd on the later synchro boxes so hill climbing might be a bit slower but easier. I hardly ever use 1st.