[TR] OD lubrication

[Dave1massey at cs.com]

In a message dated 8/14/2008 6:26:49 PM Central Daylight Time, 
standardtriumph at btinternet.com writes: 
> With regard to engagement, some overdrives 'slur' into work, others engage 
> with a mighty thump. Am I reading here that users prefer the violent to the 
> more gentle? If so, then the 'thumper' on engaging is putting a strain on the 
> engine as it somehow has to suddenly lose some 500-750rpm and the flywheel 
> needs immediate slowing. It's different on dis-engaging as an extra 500-750rpm 
> has to be found and its all the moving parts from the tyre tread forwards to 
> the engine that does this - wheel splines, diff gears, diff nose piece, hardy 
> spicers, gearbox, clutch, flywheel, crank and conrods suddenly get 
> accelerated. It's not surprising there's a jerk!

I'm with you, John.  My TR6 (J-type) has a nice smooth engagement when 
shifting into overdrive.  There is about a 1/3 to 1/2 second delay at highway (or 
highway on ramp) speeds so a little anticipation is a good thing but not a 
difficult habit to acquire.  The TR3 (A-type), however, will engage the O/D before 
the switch has finished its travel.  Although I doubt this has an adverse 
effect on the engine I do believe that slowing a 30 lb flywheel from 3500 RPM to 
2800 RPM in such a short period of time puts a lot of stress on the gears, 
bearings and thrust washers in the transmission proper and in the overdrive 
portion as well.  I've take to slightly dipping the clutch when engaging the O/D to 
soften the load.

The Big Healey's had a sleeve and smaller piston in the accumulator 
effectively reducing the size and causing a greater drop in accumulator pressure upon 
engagement softening the "blow" when overdrive is engaged.  This may be how 
they accomplished the "soft shift" to which Randall refers as used in IRS TR's.  
I, for one, am fitting just such hardware to my TR3 box as it gets 
reassembled.  I do not wish to make the gearbox rebuilds a frequent thing.

Cheers

Dave