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[Fot] Type A OD pressure test

Subject: [Fot] Type A OD pressure test
From: charly at mitchelplumbing.com (Charly)
Date: Wed, 07 Mar 2018 01:57:34 -0000
This is another I have used for reference.

www.vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf

Charly Mitchel 
TR6 #44

On Tue 06/03/18  5:25 PM , Greg Blake gblake58tr3 at icloud.com sent:
> All,
> Appreciate all the feedback. As this was my first time tearing into an
> overdrive, I am not familiar with how they work and what is
> acceptable. 
> I was following the great articles on the Buckeye website.
> http://www.buckeyetriumphs.org/technical/AOD/AOD3/AOD3.htm [1] 
> Towards the end of the reassembly section, the article discuss the air
> test which I thought could save me some trouble of trial and error. 
> I am happy that the clutch is operating as expected and plan to
> reassemble and bench test to check for operating pressure. 
> Thanks again for the advice. 
> Greg
> 
> Sent from my iPhone
> On Mar 6, 2018, at 5:20 PM, M&M Hado via Fot  wrote:
> I agree.  To me using air is not so much to test the ?seals?
> (O-rings, balls & seats, accumulator piston rings, etc.) but to test
> the mechanical movement of the overdrive internals.  Greg?s test
> showed the pistons moving the cone clutch very well with only 120 psi
> so that?s what I would be looking for on the air test and nothing
> more.  Plus, this is something you can do on the bench before putting
> it together since oil pressure is not yet available before assembly. 
> I think it?s inevitable that you will hear a lot of air leakage past
> the operating valve with this mechanical test and doesn?t prove that
> anything is hydraulically ?tight.?  The bottom line is to get the
> 400 psig and, if you do, any leakage past these areas is internal and
> a moot point. 
> Mike
> FROM: Fot [] ON BEHALF OF Charly Mitchel via Fot
> SENT: Tuesday, March 6, 2018 1:58 PM
> TO: J Wagner
> CC: 
> SUBJECT: Re: [Fot] Type A OD pressure test 
> Not to me it isn't, it's not really proving anything.  Can't tell it
> it's leaking past seals.
> 
> Charly Mitchel
> TR6 #44
> 
> ----- Original Message -----  
> 
> FROM:  
> 
> TO:  
> 
> CC:  
> 
> SENT: Tuesday, March 06, 2018 11:40 AM
> 
> SUBJECT: Re: [Fot] Type A OD pressure test
> Makes sense.  Subsequently, is compressed air a viable means of
> testing seals that normally run gear oil?
> On Mar 6, 2018, at 10:17 AM, Charly Mitchel  wrote:
> 
> I believe the answer is the water molecules are larger than the air
> molecules, which makes them easier to pass through the space.  I think
> Gore-Tex work the same way, lets the fabric breathe, but keeps the
> water out.
> 
> Not sure why I know this :)
> 
> Charly Mitchel
> TR6 #44
> 
> ----- Original Message ----- 
> 
> FROM:  
> 
> TO:  
> 
> SENT: Tuesday, March 06, 2018 8:03 AM
> 
> SUBJECT: Re: [Fot] Type A OD pressure test
> I?m almost embarrassed to chime in here as I have no expertise on
> the inner workings of a transmission, but  perhaps it?s more of a
> question than an answer.
> I?ve run a lot of PVC irrigation pipe in my day, particularly in
> the last few years landscaping my house.   I?ve noticed that
> whenever I turn on a new system, the air compressed by the incoming
> water with force it?s way past connections of threaded pipe, joined
> with teflon tape, and take a little water with it.  Just when I?m
> thinking that I?ve failed to tighten the pipe enough, the leaking
> stops once all the air escapes.  
> I suppose it?s a fluid dynamics question.  Will compressed air act
> differently on seals than pressurized oil?
> Maybe the escape of air is as meaningless as it has been in my
> sprinklers?
> ?Justin 
> On Mar 6, 2018, at 6:48 AM, M&M Hado via Fot  wrote:
> 
> Greg,
> 
> Just a couple more thoughts to add to the good suggestions already
> offered. I especially liked Jack?s idea of hand-lapping in the
> aluminum seats with a ball welded to a rod.   
> 
> I?m guessing that most of the air you?re hearing is leaking
> around the outside of the operating valve since air is much more
> likely to do so than the relatively thick 90 weight oil.  Just the
> fact that only 120 psi of air pressure is enough to move the operating
> pistons tells me that the rest of your system is relatively tight. 
> The normal operating pressure after all is about 400 psig so you have
> a lot of ?fat? built into it.   
> 
> One thing that might cause the operating pistons to move with a
> relatively small pressure is having weak or incorrect springs pushing
> the cone clutch rearward.  Be sure you have the so-called ?long?
> and ?short? ones in the right locations,  It?s actually the coil
> bound length that determines which is which.  If you put a long one
> where a short one will be, it may bind before reaching full movement,
> resulting in the cone clutch not reaching the brake ring.  Don?t ask
> me how I know this.  To check this, I put each spring on a threaded
> rod and run a nut down the rod until the coil binds.  Measure the
> length at that point and the long springs will be about 3/8? longer
> than the short ones. 
> 
> Also, the seating of the balls on the aluminum seats in the casing is
> indeed important but it?s also important to have a good seat between
> the ball and tip of the operating valve.  I had a D-type OD that was
> eating my lunch with low operating pressure during engagement and the
> tip of the valve was nicked resulting in a bad seal.  Changing the
> valve solved the problem.  The oil flow is very small in the system so
> a leak of even the smallest area will drop the pressure quite a bit. 
> 
> Lastly, you mentioned the ?relief valve? and I?m not sure which
> valve you are referring to since the pressure relief occurs when the
> accumulator piston moves enough to uncover the relief holes back to
> the sump.  Since you only had 120 psi, the accumulator piston would
> not have moved nearly enough to ?relieve.?  I?m guessing you
> were referring to the operating valve. 
> 
> Mike Hado
> 
> FROM: Fot [ ] ON BEHALF OF barry rosenberg via Fot
> SENT: Tuesday, March 6, 2018 5:31 AM
> TO: Jack Wheeler; Greg Blake via Fot
> SUBJECT: Re: [Fot] Type A OD pressure test
> 
> I used to put the ball in a tap in down with a blunt punch. As the
> case is aluminum and the ball hard steel, it made a very nice seat for
> itself. This can be done without pulling the OD apart. Just pull the
> plug, spring and little plunger. 
> 
> Barry
> 
> On Monday, March 5, 2018 5:26 PM, Jack Wheeler via Fot  wrote:
> 
> Hi Greg.  Here is a tip for you.  When I used to rebuild A-Type
> overdrives, I would "lap in" the surface that the ball sits on.  I had
> a spare ball of the correct size, and I welded a small rod to it
> (about 3/16" diam.).  Then I put a bit of valve grinding compound on
> the ball, inserted it down into the hole, then turned it back and
> forth, thus lapping the surface that the ball sits on.  This is a tip
> that Hardy Prentice gave me years ago, when we were both racing, and
> obviously the purpose was to minimize any leakage past the ball.  This
> may be to late in your case, as you would have to do this while the
> unit is apart, so that you can carefully clean all of the grinding
> compoound out of the housing after the lapping.  Maybe this will help
> you next time.  Good luck. 
> 
> Jack Wheeler
> 
> On Monday, March 5, 2018, 12:12:29 AM EST, Greg Blake via Fot  wrote:
> 
> 
> All knowing FOT
> 
> Attached is a video of my Type A OD unit ready to bolt up to the
> transmission. I decided to do a pressure test with 120psi of
> compressed air plumbed into the operating vale port.  
> 
> The engagement seems to work well when I move the operating lever.
> But I am concerned about the amount of air that can be heard leaking.
> I believe it is going past the relief valve. Is this abnormal amount
> of leaking?
> 
> I noticed upon tear down that the nonreturn valve had a 1/4" ball
> instead of the 5/16" this unit should have had. The test you see in
> the video is with a new 5/16" ball. I am sure on a previous rebuild
> someone mistakenly used the later style 1/4". 
> Just wanted opinions before I buttoned this up to the transmission for
> some bench testing. 
> Thanks. 
> 
> Greg
> 
> Sent from my iPhone_______________________________________________
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