Re: TC lockup problems

[Roger Heflin <rah@horizon.hit.net>]

On Wed, 28 Jun 2000, Rick Lindstedt wrote:

> Roger Heflin wrote:
> >Beyond the "table" that is listed, there is a hard lockup in my
> >computer (93 LT1 Z28),  of 95 mph, and it will lockup at that no
> >matter what the TPS is.   I would expect that yours also has it, the
> >value is not in a table, it is all by itself and outside the table.
> 
> AH HA!!! SO that what is causing mine to do this!!  Mine is at 80mph tho.. 
> and I havent ever noticed this until I got my Vigilante convertor....
> 
> and speaking of TCC stuff... as I am going down the road... let off the gas 
> but DONT hit the brake...the convertor seems to want to hunt as in  lock / 
> unlock / lock / unlock .. it will do this until 70mph (decelleration) and 
> all is fine... but anything above that when I "coast" it does this.. .any 
> ideas??
> 

In that flowchart there are some things for coast, I know at certain
speeds it will leave the convertor locked while coasting, and it may
be entirely controlled by that table.

On mine when I was getting the lock/unlock (or more correctly
driveshaft chatter), the TCC was not actually locking/unlocking, it
was I believe the bigger cam causing rpm instabilities when the TCC
was locked.  On mine I had to raise the TCC min lock speed from
48(L)/45(U) to a higher speed (I don't remember which but I moved it
at least 10mph higher).   I only had this problem with stock gears,
and a more aggressive cam, I suspect that the GM default was lock it
as low as it could be locked without getting this sort of behaviour,
and that putting a bigger cam raises the speed that this becomes a
problem at.   Mine was a problem at both coasting and very low TPS
resulting in maintaining the speed or just accelearting a very little
bit in the 48+ mph range.   I believe mine was obvious up until about
60mph, at 60 you could hear it if you where really careful, but only
just barely, and not enough to be really annoying.   To get this
behavior the TPS needs to be low enough to not unlock the TCC and low
enough to not cause a downshift leaving the car in high gear.

			Roger