90 SP36 downshifting

[williamcharrison]

I just returned from a 500 mile trip in my BB and everything was fine
except that the transmission did not downshift correctly on long steep
hills. If the hill was steep enough the coach would almost stall
unless I pressed down on the accelerator quickly.
Come to think of it when accelerating from a stop the upshifts
seem to occur very close together also. If there is a simple fix I
will attempt it myself, otherwise I need to find someone close to
Akron, Ohio to make the adjustment/repairs. (The trans. econ/pwr
switch was on pwr).

[Harvey Lawrence]

--- In WanderlodgeForum@yahoogroups.com, "williamcharrison"
wrote:
> I just returned from a 500 mile trip in my BB and everything was
fine
> except that the transmission did not downshift correctly on long
steep
> hills. If the hill was steep enough the coach would almost stall
> unless I pressed down on the accelerator quickly.
> Come to think of it when accelerating from a stop the upshifts
> seem to occur very close together also. If there is a simple fix
I
> will attempt it myself, otherwise I need to find someone close to
> Akron, Ohio to make the adjustment/repairs. (The trans. econ/pwr
> switch was on pwr).

I do not know tht much about ZF transmissions but it sounds like the
Transmission speed sensor may have a problem and/or the tranny shift
points need to be reset. Look in Your ZF literature for a close
service center. Barring that a truck tranny service center.Sorry I
can not be of more help.

[fred89sp]

What you experienced may be normal unless this represents a change
from your prior experience on this coach.

I just came back from a trip in my 89SP in which I encountered a long
hill that I often drive. I started the hill at 70 MPH but was soon
down to 25 with much black smoke out of the exhaust.

The transmission does not have a downshift switch like a car that is
activated by pushing the pedal to the floor. In fact I have found
that when RPMs drop you can get it to downshift by backing off on the
pedal. Also hit the lower shift selector buttons, this will not force
a downshift and you cannot damage the transmission by doing this
because the computer has the final say. What it does do is keep the
transmission in the lower gears once it does downshift. You can then
keep the revs up but be ready to hit the next button up when the
engine gets up to 2,800 RPMs.

If you still have concerns take it to ZF at Vernon Hills outside
Chicago to have them check it out. In general this is a bulletproof
unit and they know exactly what they are doing. They can also
re-program your PROM for an update that was done a number of years ago
that changes shift points. They will also explain how best to operate
the transmission.

The only thing you can easily adjust is the throttle position sensor
(or do they call it the load sensor). Check your ZF literature. Also
call ZF, they are very helpful.

Overall it is frustrating to see RPMs drop so low and have the engine
lug but that tends to be the nature of the beast.

--- In WanderlodgeForum@yahoogroups.com, "williamcharrison"
wrote:
> I just returned from a 500 mile trip in my BB and everything was fine
> except that the transmission did not downshift correctly on long steep
> hills. If the hill was steep enough the coach would almost stall
> unless I pressed down on the accelerator quickly.
> Come to think of it when accelerating from a stop the upshifts
> seem to occur very close together also. If there is a simple fix I
> will attempt it myself, otherwise I need to find someone close to
> Akron, Ohio to make the adjustment/repairs. (The trans. econ/pwr
> switch was on pwr).