Please visit the Club's website https://www.dloc.org.uk/ to join. Visit https://www.dloc.org.uk/adhoc to DONATE towards the cost of the forum.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.

Pre-selector gearbox over haul

qantasqf1
Posts: 299
Joined: Mon Mar 07, 2016 10:13 pm

Re: Pre-selector gearbox over haul

Post by qantasqf1 »

Well, Hugh, if the gears had overheated to the point of discolouration then something was seriously wrong because that should never happen. Given this and the fact that the bushings were badly worn (also unusual since there is no end thrust on the epicyclics) then it sounds very much like the oil pump had failed and/or the oil galleries were blocked, starving the entire running gear of oil. Either that or the oil level was far too low.
A twisted input driveshaft is a classic symptom of, er, questionable driving practices because it’s almost certain reverse had been preselected then engaged with the car moving forward, or a forward gear had been engaged while the car was still moving in reverse... and I’ve got such a shaft in my spares box to prove it! (No, it wasn’t me.)
Steve

Stan Thomas
Wise Man
Wise Man
Posts: 795
Joined: Sat Feb 13, 2016 2:14 pm
Location: Penkridge. Staffs.

Re: Pre-selector gearbox over haul

Post by Stan Thomas »

Quite right! - the first motion shaft can be twisted if too low a gear is selected at speed, as there is no "safety" mechanism to prevent it, as in a modern auto box. I've even known a half shaft supposedly being snapped by changing down from too high a speed. ............. which leads me on to another story.

When I was "serving my time" on Daimlers, the foreman told us that before the war and as a demonstration, a Daimler was driven over Wales with the brakes disconnected and the car controlled by using the gearbox alone.

Believe that if you will!!

Roark
Posts: 161
Joined: Sat Feb 13, 2016 10:52 am

Re: Pre-selector gearbox over haul

Post by Roark »

This afternoon I had intended to take the gearbox to be steam cleaned but that wasn't possible. Just to ensure, should they need to turn the 'box on its back I decided to drain the oil. I made sure it was level, undid the drain plug and was rather disappointed to see a stream of black oil fill up the bowl. There was a slight "hint" of gold colour but most was black. The drain plug is concave in the hollow was some grey gunk, rather like graphite grease.
I had not imagined, from the helpful comments posted in reply, that my gearbox with 68,000 miles under its belt would have produced anything other than nice clean oil.
Back to the "drawing board". Heavens this "restoration" resembles the tug of a loose thread on a cardigan/jumper which fits the wearer well below the knee. Now it resembles a pelmet/tank top or brassiere.

terryfrombury
Posts: 154
Joined: Fri Feb 12, 2016 10:25 pm
Location: Cheshire, UK

Re: Pre-selector gearbox over haul

Post by terryfrombury »

Oh come on, Roark, no need to introduce vulgarity into this learned discourse! Brassiere indeed!!! Hold on, now!

Apart from vulgarity, you are obviously an optimist. I think that to expect golden oil is a little too much. The fact that there was a hint of gold is far better than the state of the oil in my box when I got it.

qantasqf1
Posts: 299
Joined: Mon Mar 07, 2016 10:13 pm

Re: Pre-selector gearbox over haul

Post by qantasqf1 »

I read in some authorative publication from the early 30s that a preselector can be used to slow the car by...wait for it...engaging reverse while travelling forward at 20 mph. My God! Pioneering days indeed! These boxes must have been a regular source of mystery in those far-off days. A November 1933 edition of Iliffe’s Motor Cycle magazine published the engineering drawing of the 500cc BSA preselector box...upside down.
Steve

Stan Thomas
Wise Man
Wise Man
Posts: 795
Joined: Sat Feb 13, 2016 2:14 pm
Location: Penkridge. Staffs.

Re: Pre-selector gearbox over haul

Post by Stan Thomas »

The drawing was the right way round - it was the magazine that was upside down!

Post Reply