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[Fot] Type A OD pressure test

Subject: [Fot] Type A OD pressure test
From: gblake58tr3 at icloud.com (Greg Blake)
Date: Tue, 06 Mar 2018 19:25:26 -0600
References: <7DF32ACB-8C68-45A3-9654-C743E3FB3C1A@icloud.com> <1967427720.8517669.1520273071794@mail.yahoo.com> <1123716743.11727331.1520335836458@mail.yahoo.com> <003901d3b55a$3503c540$9f0b4fc0$@att.net> <4774C90B-FECF-420A-9343-42AEE8D920F9@gmail.com> <DAD9EECD8E984095A04E4B01039A3E38@Charly> <8611DCE6-95F7-4A94-A0D0-BBD418DF2927@gmail.com> <30309331F4DE4A769A7D35F325826051@Charly> <00e901d3b5a1$c821b250$586516f0$@att.net>
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

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 <fot at autox.team.net> 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 [mailto:fot-bounces at autox.team.net] On Behalf Of Charly Mitchel 
> via Fot
> Sent: Tuesday, March 6, 2018 1:58 PM
> To: J Wagner
> Cc: fot at autox.team.net
> 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: J Wagner
> To: Charly Mitchel
> Cc: fot at autox.team.net
> 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 <charly at mitchelplumbing.com> 
> 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: J Wagner via Fot
> To: fot at autox.team.net
> 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 <fot at autox.team.net> 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 [mailto:fot-bounces at autox.team.net] 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 <fot at 
> autox.team.net> 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 <fot at 
> autox.team.net> 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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