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Re: transmission lockup

To: "Andrew D. Zimmerman" <a.d.zimmerman@worldnet.att.net>,
Subject: Re: transmission lockup
From: Max Heim <mvheim@studiolimage.com>
Date: Sat, 6 May 2000 18:40:56 -0700
Well, if you don't have power to the OD unit, it shouldn't be engaged at 
all. The 3rd/4th gear lockout switch cuts power to the OD when you shift 
out of 3rd or 4th, so it would have no effect with power cut off to the 
OD in general. So you may well want to jumper power to the OD just to see 
if the solenoid activates, and possibly if the lockout switch is really 
working (I would have bench tested this before installation in the car, 
since it is pretty much inaccessible. It also may have required some 
small adjustment via shim washers).

But the real issue is why is the transmission "locked up"? And what 
exactly do you mean by "locked up"? I assume you mean that in any gear 
(1-4), you can't push the car and make the engine turn over (as you tried 
to do in order to adjust the valves). Are you sure the parking brake was 
released? Did you try it with the transmission in neutral? You may want 
to raise the rear wheels off the ground and try turning the engine over 
with a wrench on the crackshaft pulley nut (remove spark plugs to relieve 
compression first).

I don't know of anything the OD could do that would cause this symptom. 
Whether the OD is engaged or not, the transmission would still turn 
freely, albeit at a different ratio. The only thing I can think of is the 
plunger for the pump which pressurizes the hydraulics in the OD. It runs 
off a cam on the main shaft. If it were improperly installed or jammed 
somehow, it could conceivably prevent the shaft from rotating. This would 
necessitate removing the OD unit from the transmission to confirm and/or 
repair.

Before you despair about removing the entire engine/transmission unit 
again, I have found that it is possible to pull the OD off the back of 
the transmission from underneath the car. You do have to go through every 
step of engine removal up to to the point you start hoisting it on a 
chain. But instead of using an engine hoist, you jack it up from below 
with a floor jack, positioned so that it can roll forward as it lifts. 
Another floor jack beneath the transmission is also helpful. Basically, 
the idea is to lift and inch forward the engine and transmission until 
the tailshaft clears the rear (permanent) crossmember. Then you lower the 
rear of the transmission enough to pull the OD out and down. The 
advantage compared to pulling everything is that you don't have to rent a 
hoist, and you can do it by yourself (slowly and carefully). Remember to 
drain the transmission oil first so as to limit the flood to a couple of 
pints.

If you did not have the OD separated from the transmission previously, 
you will find out how the pump plunger needs to be manipulated in order 
to remove the OD unit (it kind of catches on the cam and needs to be 
depressed against its spring with a thin flat screwdriver inserted into 
the gap, while you pull back on the OD). Reassembly requires a similar 
maneuver, and it is the failure of this step that I suspect caused the 
problem.

Before jumping to any conclusions, I would consider soliciting the advice 
of an experienced transmission expert, whether locally or on the list. 
The advice above is based strictly on my experience, and there may be 
other, simpler causes and solutions of which I am ignorant.

I have also experienced a situation with a 4-synchro transmission where 
the shift lever would lock up, preventing me from changing gears at all. 
But this does not seem to match your symptoms. Just for the record, it 
was due to the interlocking arm being misadjusted (or so I recall). 

Good luck.

Andrew D. Zimmerman had this to say:

>This is a multi-part message in MIME format.
>--------------C49C23F2206F9314F4E2056B
>
>All,
>
>I am in the final stages of a restoration of a 72 'B.  Engine and body
>completely overhauled and upgraded.  Only minor work on the tranny
>though--new o-rings, etc. in o.d. solenoid (and as far as I know,
>everything went back in the proper position and order).  Put
>engine/trans. back in car and reinstalled everything, to get ready to
>try the big crank-up.  My last posting described a problem getting the
>shifter to move into gears.  That problem was resolved by removing a
>rather annoying, longish switch for the seatbelt warning system, which
>was apparently blocking movement of the "remote control" shaft (kinda
>like removing an appendix--it's there causing all sorts of Hell, does
>little if anything productive).  Now that the unit shifts beautifully
>into all gears, I thought I was now ready to check final settings,
>intall battery fill engine fluids, and crank her up.  Wrong.  Upon
>putting tranny in 4th gear to "rock" valves open and closed to adjust
>clearances, I discovered the tranny was locked up.  Same in 3rd; also
>same in 1st and 2nd.  I suspect the o.d. unit somehow got engaged during
>work on piston/o-rings, or other movement of tranny outside of the car.
>
>The Bentley manual mentions the possibility of a sticking o.d. clutch.
>Could this lock up motion in all four gears, not just 3d and 4th?  They
>recommend vigorous blows with a rubber mallet to the brake-ring.  I'm
>about to try this.  If this doesn't work, does anyone have any other
>knowledgeable suggestions?  If I hook up a battery, will proper
>placement of the o.d.  (i.e., wiper/washer) switch cause the unit to
>disengage?  What else should I try?
>
>Thanks for your help!   Andrew Zimmerman
>
>--------------C49C23F2206F9314F4E2056B
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>n:Zimmerman;Andrew D.
>tel;home:(302) 737-7747
>tel;work:(302) 888-5293
>x-mozilla-html:FALSE
>adr:;;10 Woodshaw Road;Newark;DE;19711-7421;USA
>version:2.1
>email;internet:a.d.zimmerman@worldnet.att.net
>note;quoted-printable:"Freedom is not static but dynamic=3B not a vested 
>interest, but a prize continually to be won."  (Jacques Ellul, The 
>Technological Society)
>fn:Andrew D. Zimmerman, Ph.D
>end:vcard
>
>--------------C49C23F2206F9314F4E2056B--
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>


--

Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.


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