Re: am i hurting my gearbox?

"Noddy" <me@[EMAIL PROTECTED]
> wrote in message 
news:47a7d3aa$0$90072$c30e37c6@[EMAIL PROTECTED]
>
> "RogerM" <RogerM@[EMAIL PROTECTED]
> wrote in message 
> news:13qfhj3na5akdad@[EMAIL PROTECTED]
>
>> I understand that. I actually meant matching the revs as sure as ****
(as 
>> you accurately mentioned) the grinding of the cones would occur if you 
>> didn't. I guess from many years of driving semis back in the 70's and 
>> 80's I learnt how to do it and I still do it occasionally (when 
>> down****fting) in cars.
>
> Large trucks are different (at least most American ones anyway) in that 
> they use a direct mesh trans. The popular Road Ranger is a good example.

> Every gear is a "crash" gear with no synchronizing ability of any kind. 
> The gears have rounded shoulder teeth to help with the engagement, and
as 
> long as you've got the rpm within cooee of where it's supposed to be the

> gears will just about fall in (unless of course you're talking about 
> oddball things like 13 speeds that have a split on the high ratio gears,

> as they're famous for getting a bunch of false neutrals).
>
> With a synchro box each gear has a bevelled running face that the
synchro 
> cone grabs on to and acts like a "brake". As the lever is pulled into a 
> gear, the cone seats itself onto the bevelled edge and "brakes" the gear

> (either by slowing it down or speeding it up) so it's speed is matched
to 
> that of the synchro hub and the spines can engage without crunching the 
> crap out of themselves.

Why is it that 2nd gear always appears to be the gear that the synchro has

trouble with. I'm not saying always, but I have noticed over all the years

of driving many manuals, once the vehicle gets around the 100K on it,
there 
would be sometimes difficulty in putting the gear back to 2nd when
cornering 
for instance? Other gears are always fine, just 2nd and is there an 
explanation for this? The example would be if you are accelerating and
going 
from 1st to 2nd and say for whatever reason, you are too slow in changing 
gears and the engine revs go back to an idle, more often than not, it is
not 
easy to engage 2nd gear and sometimes there will be a slight (or sometime 
major) grate. The same when down ****fting only it is usually worse. The 
other gears (3rd, 4th and 5th) never seem to be affected by this
phenomenon.
>
> Without using the clutch, the synchro isn't capable of speed matching
the 
> mainshaft as the engine has control of it, and all you'll achieve by 
> trying is wearing the crap out of the cones in a big hurry.

So, even if one "revs" the motor to match the revs of the gears and it
goes 
in easily (hmmmm, my mind is beginning to boggle here) without grating, 
is 
it still doing damage to the cones?

In your "mechanical days" did you ever come across a box that you had 
difficulty in putting back together after dismantling for service? I guess

you possibly had access to workshop manuals.

Beers & Cheers

Roger