[Healeys] Russ Thompson

Bob Spidell bspidell at comcast.net
Wed Aug 9 09:25:09 MDT 2017

Good info!  Just how much harsher is engagement with the larger 
accumulator?  As one who always tries to shift as smoothly as 
possible--without slipping the clutch much, if any--is engagement so 
harsh as to require a slip of the clutch which, of course, will 
contribute to clutch wear?  If clutch isn't used, is engagement so harsh 
as to be a 'shock' to the drivetrain; i.e. U-joints, splines, 
differential gears?


On 8/9/2017 5:58 AM, Ed O'Neal wrote:
> Mike,
> The original OD design used a 1 ¾” accumulator piston with a 
> concentric double spring.  This configuration was used in a lot of 
> different vehicles including the Triumphs.  Donald Healey didn’t like 
> how the OD engaged harshly when the clutch was not used during the 
> shift.  He changed the design to incorporate a sleeve fitted in the 1 
> ¾” bore with a smaller 1 1/8” accumulator piston inside of the sleeve 
> and a single spring.  This gave a slower engagement much like a modern 
> automatic transmission.  However, as the OD wears the internal leakage 
> increases and the OD will engage very slowly or not at all.  Using 
>  the larger accumulator is a good idea (in my opinion) and will delay 
> the point when internal leakage causes a problem.
> Ed
> ed at wadsworthoneal.com <mailto:ed at wadsworthoneal.com>
> Edward J. O’Neal, P.E., Pte.
> Wadsworth O’Neal Associates, Inc.
> 6418 Commerce Park Drive
> Fort Myers, Florida  33966
> phone: (239) 245-8728
> cell: (239) 410-6174
> *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of 
> *Michael MacLean
> *Sent:* Tuesday, August 08, 2017 8:47 PM
> *To:* Healey List
> *Subject:* [Healeys] Russ Thompson
>      Through a reference from the list I am having Russ Thompson in 
> Northridge, California rebuild my BN2 transmission.  It is a low 
> mileage (10,000 mi. approx) transmission, but I wanted to be able to 
> put it in and not have to take it back out again.  Good thing I took 
> this precaution.  Russ found the overdrive stuck and would never have 
> worked.  Today he showed me the accumulator piston.  The smaller 
> center piston was scored from dirt or crap in the oil.  Russ replaced 
> it with a one piece piston from a Triumph overdrive.  There was a huge 
> spring below it.  Anyone heard of this?  He said engagement will be 
> real positive now.  Even with the low mileage, the number 2 synchro 
> was toast and will be replaced.  The other two were fine and will be 
> re-used.  All the gears showed very little sign of wear.  The reverse 
> gear had some surface rust on the teeth, but that can be blasted and 
> it will be fine. Getting closer to having the drive train is the car.
>      I know I am going to start a discussion, but Russ recommends 
> using 40wt motor oil for the transmission.  Anyone know what weight 
> Redline MTL is?
> Mike MacLean

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