5spd surprise

[Jeff Miller]

No problem.

The MT-643, standard WLFC transmission, has four gears. The shift
goes like this: 1/2, lockup, 2/3, 3/4.

My speed reference might be a little off for the 5.29:1 gears, it has
been a while since I always sent my 5.29 gears to the junkyard, but I
believe it locks the torque converter when in second gear around
37mph at full throttle, will drop back out of lockup about the same
speed at full throttle. Select second at a stop, you will feel the
1/2 shift, then the lockup. This should tell you conclusively that
with two shifts in the second gear position you are feeling the
lockup.

As said before, the true 5-speed (the 654cr) is in the PT models with
the 6-cylinder DD engine, the MT-643 in your bird is maxed-out at
250hp.

A five-speed is not necessary IMO on the 3208, it has a good useable
RPM range to 3000rpm (Na and ATAAC, 2800rpm for Ta), it just needs
more power and taller gears for highway work above 55 or 60mph. The
DD 2-stroke engines really needed the 5-speed more as they're only a
2100rpm engine with a fairly narrow power band.

- Jeff Miller
in Holland, MI



--- In WanderlodgeForum@yahoogroups.com, "davidkerryedwards"
wrote:
>
> I'm more confused than ever. There is no doubt I'm feeling 5
> engine/tranmission speed transitions. It's possible I'm confusing
the
> lock-up for a shift. There is information in the owners manual on
two
> allison transmissions, a 644 and a 654CR. The 654CR does not have a
> creeper 1st gear although reverse is way lower on the 54 than the
44.
> The information shows the 644 locking up at the top of first gear.
If
> I were to make a guess as to which transition was a lock-up, I'd be
> inclined to think it was the transition at the top of first gear.
> However, when climbing the 10% grade out of Palo Duro canyon, I kept
> the shift lever in 1 and I never felt a lock up or shift. Perhaps
it
> does not lock up at the top of first gear if the shift lever is
on '1'.
> I crawled under today to see if I could tell if it was a 644 or 654
> since I have pictures of both, but couldn't get a clear enough view
to
> tell.
> One thing that made me start analyzing what was happening was that
> when climbing, it would drop from top gear into the next lower
gear, I
> could then move the shifter into 3 and it would hold that gear.
> However if it shifted down twice from top gear, and then I moved the
> shifter into '2' it would downshift again into a lower gear. I
> thought two gears down would be '2' and putting the shifter in '2'
> would simply hold that gear and stop it from shifting up.
> Does anyone know the difference between a 643 and a 644., if that is
> what I have? Top shift at full throttle is around 43 or 44mph.
>
> Kerry
> 82 FC 35
> Denver