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[Fot] Type A OD pressure test

Subject: [Fot] Type A OD pressure test
From: 4msonset at gmail.com (J Wagner)
Date: Tue, 6 Mar 2018 11:40:34 -0800
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>
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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>> 
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>> 
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