[TR] A Type OD

David Massey dave1massey at cs.com
Sat Apr 21 06:21:50 MDT 2018


Terry, congratulations of retiring.  I am looking at that change-of-life transition in the next year or two.

One possible cause of the solenoid dropping out and/or chattering is the isolator switch (or lock-out switch or enable switch, what-ever) is adjusted right on the harry edge of operation.  As things warm up and expand the dimensions change ever so slightly and the switch is no longer engaged.  You may have inadvertently fixed that when you replaced and shimmed those switches.

You can test it with the rear wheels off of the ground and there is no real need for increasing the idle speed.  With no load on the engine you will find that the engine speed doesn't change when you engage but the speedometer will jump up as the wheels will be spinning more quickly.

There is no reason that the OD should disengage more slowly when the car is not moving.  The valve will dump the pressure at the same rate regardless.  Unless something is sticking and the vibrations from the car moving helps things move.

 

 

Dave Massey


 

 

-----Original Message-----
From: TERRY SMITH <terryrs at comcast.net>
To: triumphs <triumphs at autox.team.net>
Sent: Sat, Apr 21, 2018 5:43 am
Subject: [TR] A Type OD



Hello, everyone.  

I've had overdrive issues with my TR3 since having it rebuilt two years ago.   The first issue was that it wouldn't drop out of OD.  Inspection showed that the shop that rebuilt it had put a bolt in to use as a stop for the solenoid plunger so it would not drop down too far to pick up again.  Good so far.  But he hadn't followed through with a nut on the bottom of the bolt to hold it securely.  Result was that sometime during the transit from the shop to home, or during finicky re-installation of the tranny into the car, the bolt rose up and got cockeyed, such that the plunger couldn't drop down.  If I waited a day, though, it would.  Whatever, I fixed that with a new bolt/nut and the OD came out of of OD when and as it should.

My biggest worry was that before I knew the car wasn't disengaging OD, I tried backing up.  I met some substantial resistance and am pretty sure I didn't power through it.  OD seemed to work okay after the fix, so subject to your advice, am thinking I didn't overly damage the  OD.

Next, the OD would work for about 20 minutes, then drop out.  A few times I could actually feel it chatter as it rapidly kicked in and out before dropping out altogether.  That made me think it was likely electrical.  I swapped out the solenoid, relay and the OD switch.  No improvement as intermittency remained.  

Now I've retired (end of January) so can spend a bit more leisure time looking into this.  

I've starting by rewiring from the relay forward so I know all the contacts are good (some are spade connectors on the isolator switches were almost 60 years old and felt loose and despite spraying with electrical contact cleaner, oily).  I've replaced the isolator switches too since I'm in there and seemed to have buggered up the spade terminals on the old ones, bending them but not severely during tranny or tunnel reinstall.  I've tested them with a multimeter using the spacer washers provided and they test good in all three gears.  I've tested the solenoid using power direct from the battery and get a very satisfactory snap when it kicks in.  But here's the thing:  when I've tested with all the circuits connected--that is, the relay and switch, the snap isn't pronounced, but the solenoid does kick in as it should.  

I've adjusted the actuating lever to the solenoid so that it's backed off from the o-ring, and made sure it doesn't kink the plunger from dropping.  I did this per the book, using the 3/16 drill bit, which assumes that operating oil pressure is sufficient then.  I've also pulled the operating valve spindle and blew through it with lung power.  It let air through.  To be sure, I blasted it with compressed air and (hmmm) to my uneducated sense it seemed to blow through better, meaning there may or may not have been some small restriction in the channel.  We'll see.

So...where am I.  Next step is to jack the rear of the car up and put it on stands so I can run the car and put it in OD to see if it kicks in and out.  Then run it awhile to see if it stays in.  

Now the questions:  

1)  Am I okay to assume that adding the additional circuitry will reduce the "snap" sound when the solenoid kicks in.  Or is that sound even relevant as long as the solenoid actuates.

2) When I test the OD on blocks, do I need to increase engine speed beyond idle to get a proper test.

3) If the thing still tests sketchy, where can I get an oil pressure gauge that will screw into the operating valve so I can really know what's going on?

4) Do I remember correctly that after turning off the OD with the car stationary, it takes longer than when it's actually on the road?

Thank you, everyone, for your patience with this ridiculously long post.

Best,

Terry Smith, '59 TR3A  TS 58667

New Hampshire



 

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