The 68 LeBaron I purchased 3 months ago has a lockup converter. Here is
the info I have about these. Torqueflites for 440s with lockup converter
appeared for the first and last time in 1978 (last because the Chrysler big
block expired after 78). So, I presume my converter is from 78. According
to Bob, my whole transmission must be a 78 since the lockup converter
cannot be bolted on earlier transmissions. Here is how it works. While
accelerating smoothly and slowly, and after 3rd gear engaged and at about
33-35 the converter locks up. At these low speeds, the converters are
quite inefficient, and there is a lot of slippage (about 40% if
accelerating harder than usual, about 20-25% usually, I have the low stall
speed unit). So, when the converter locks, it feels as if you shifted to a
high gear. From then on, the converter stays locked with 0 slippage. If
you accelerating with lower gears (remember, you can hold 1st up to 50 if
you need maximum acceleration) the converter stays "unlocked" till high
gear engages. The efficiency benefit is more evident at low cruising speeds
because at highway speeds (say 75 mph) the engine speed is fairly high
(~2500 rpm) and the slippage of the standard converter is a lot
lower. Unfortunately, if you are climbing a steep hill or accelerating
harder even at highway speeds, the converter will "unlock". At 80 for
example (2600-2700 rpm) if you floor it, you will see the rpm jumping
another 150-200 rpm (~8% slippage). I think (but not completely certain
yet) that even at 90 or 100 constant crushing, the converter is unlocked
due to the high relatively high load required to sustain the speed. At
these speeds though, the hydraulic coupling gets very efficient allowing
very little slippage (approaching 1% even at WOT at over 4000 rpm or over
120 mph).
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
>
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