[Fot] A-Type Overdrive Slipping and Coil Bind

[Larry Young]

Mike,
Randall made a good point about the springs.  I measured several of 
these for my articles at vtr.org.  The length difference was much less 
than 1/8 inch.  The most important difference is the wire gauge.  The 
long springs have a larger wire gauge which causes the coil bind 
differences you've observed. 

The pressure spec on the A-types is 360 psi for the early ones with 
large accumulators and 450 for the later ones.  I've seen pressures of 
650 recommended for racing, but I think that is overkill.
Larry

M&M Hado wrote:
> Ed,
>
> That's a great thought and Randall had also suggested the possibility of
> coil binding and I had not considered that.  I have a spare unit and
> measured the distance between the seating surfaces of the springs and it's
> about 3 1/32" on the inner land (for the shorter springs) and the outer is
> about 3.5".  Also, when the OD is engaged, this distance is reduced by 1/16"
> to 3/32" depending on the wear of the clutch.
>
> I then measured the length of the springs when they are coil bound and the
> long ones are around 2 15/16" on average and the short ones are 2.5".  Do
> the math and you can see that if the longer springs are used where the short
> ones should be, they will be right at the binding point when the OD is
> engaged.  The compressed spring absolute minimum length is 2 15/16" and the
> space to put it in is the same, or slightly less!
>
> Most of the OD's I've done have about the same size springs +/- 1/8" so I
> simply put the slightly shorter ones on the inner lands, thinking there is
> plenty of space.  Clearly there is the possibility that they will bind.
>
> Thanks, again, for your suggestions and I'll let you know how it goes after
> I take this apart for the third time.  Lessen learned.
>
> Mike
>
> -----Original Message-----
> From: fot-bounces at autox.team.net [mailto:fot-bounces at autox.team.net]On
> Behalf Of Ed Woods
> Sent: Sunday, May 02, 2010 7:04 PM
> To: fot at autox.team.net
> Subject: Re: [Fot] A-Type Overdrive Slipping and Coil Bind
>
>
> List,
>
> Some of the brand new spring sets are furnished with springs of equal
> length. I recall installing one set successfully but was very concerned
> about coil bind, having measured the collasped length of the inner (red)
> spring and made an educated guess of the available space within the
> overdrive. ISTR that there was 1/16" of an inch to spare. Since then, I've
> been buying sets from TRF than have some differential between the short and
> long springs, although not quite the 1/4" the manuals spec.
>
> Ed Woods
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