lock up torque converter on my 68, was for 57

[Bob Harris <b1werks2@xxxxxxxxxx>]

Re my previous notes on the Lock Up Torque Convertor

First - I had two errors in the previous letter. One was the year in which
they were offered - I said in the mid sixties - it should have been the mid
seventies. Second, the reason for inability to rebuild the unit is because
the ring gear is welded to the front cover and impeller, not the housing - a
bad term.

These convertors are not inefficient at the lower, (accelerating), speeds -
the whole reason for the addition of the turbine and stator made the old
fluid coupling ideas obsolete and provided much enhanced accelerating
performance. They have a multiplier factor of 2.2 to 2.6 compared to older
fluid couplings- but the downfall of all fluid clutch drives is the
inefficiency at the higher speeds - the slippage gets so bad that fuel
mileage suffers while it just sloshes around in there - hence the properties
of a friction clutch get very desirable. This thing locks up and so does the
efficiency. The result is a drop in rpms and increase in mileage for the
same rpms. The lock up change shouild be imperceptable. It is most important
that the car weight, rear axle ratio, engine rating and other factors be
compatable to have all this  work right - which they do.

These convertors reference the drive shaft rpms as orders to change the oil
pressure to the  Lock Up Valve and the Fail Safe Valve  The Fail Safe Valve
will permit lock up only when there is sufficient oil pressure to operate
the transmission front clutch. This same valve also provides fast
disengagement of the lock up when heavy acceleration is demanded. Again, at
the higher road speeds that you mention,  - 80 to 90 mph, the convertor is
still in lock up mode. When you encounter a hill, then the shaft rpms will
drop, and the convertyor will unlock. This returns the transmission to the
conventional 3rd gear, revs go up, car goes up the hill.

If the performance is not satisfactory, the Torque Convertor Stall Teat
should be made  - according the Service Manual instructions. If the
overheated condition for this test is longer than 4 seconds, the unit will
be damamged. some slippage is allowed, but you'll need the Stall rpms to
determine this - oil pressure checks can determine the extent of slippage.
Unlocking the Torque convertor must not be confused with Kick-down. They are
different and both work as req'd depending on load but mechanical and
driver's desires. If your car is shifting early and you have to manually
shift it then you're either asking too much of it or it needs the oil
pressure points check to verify shift point versus rpms. There were 14
different engine applications for this device for four transmissions with
three match-up identifiers and two stall speeds.I hope that I've clarified
this somewhat - a nice feature....Bob Harris
----- Original Message -----
From: "D. Dardalis" <dardal@xxxxxxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Tuesday, January 22, 2002 5:21 PM
Subject: Re: IML: lock up torque converter on my 68, was for 57


> The part that I am not sure and possibly Bob can explain is how does the
> unlocking mechanism triggered when the load is increased?  Is there a
> connection to the kick-down so that the valve operating the lock-up
"knows"
> the throttle position?  My other question to Bob or who-ever is the
> following.  If left in drive, this transmission shifts way too
> early.  1st-2nd at 10 mph, 2nd to 3rd at 20.  Even if accelerating hard,
it
> still persists at about the same shift points.  So, for now, I shift
> manually from 2nd to 3rd at about 30.  I tried to adjust the cable, and
> reached its limit with no difference.  Should I add an extension so I can
> adjust even more?  I am reluctant to do that because the previous
> adjustment had no effect.
> D^2
>
> At 10:33 PM 1/22/2002 +0100, you wrote:
> >Hi all
> >In an earlyer post I was reading about a torqe convertor that lockes up
at
> >higher rpm
> >is a convertor like this only for later models or can i get one for my 57
> >I know stuped question but I don't know much about the convertor and
> >transmision thing
> >Scared to even look at it Tryed once to do transmision job myself and
ended
> >up with a box full
> >of parts and had to go to a repairshop with it
> >thanks
> >Remco
> >57 4dr ht
> >
>
>
>
>