A coworker recommended Eldon Transmissions here in Edmonton as a good sho=
p
at trouble shoot and repair while not extracting the maximum money.
>
After an extended test drive with the mechanic today he found that, as I
reported earlier, the shifts were inconsistent.
>
Further it was found that what was actually causing the high revs when
starting the coach moving was that the coach was starting out in 2nd gear=
.
>
On a couple of occasions during the test drive it even started out in hig=
h
gear!
>
I was told that the vacumn modulator and the govenor were suspects.
>
Once up on the lift the mechanic found that at some time in the past the
vacumn modulator had been replaced with a poor quality part.
>
The govenor was found to be O.K. (The only change to the govenor was to
install a different spring to satisfy my request that low throttle shifts=
occur at lower speeds.)
>
The oil was not burn't, nor were there signs that the oil had been change=
d
to hide burn't oil during the motorhome sales process (grime undisturbed =
at
pan to transmission connection)
>
With only the modulator change, the govenor spring change, oil and filter=
change the transmission now consistently starts out in 1st gear and on
light throttle will upshift to 2nd at about 22 mph and to 3rd at about 30=
mph. Much more as I expected it should be.
>
The engine is not forced to spin the convertor up nearly as high and the
torque convertor has a much easier time of it.
>
I was pleasantly surprized to find that the modulator could cause so many=
symptoms. The modulator did not show any physical signs of total failure
(no transmission oil found in the vacumn line).
>
The transmission still shifts extremely softly so I still want to add the=
shift kit at some time in the future (although when I do so I think I wil=
l
leave the govenor spring as it is). At the time I install the shift kit I=
will change over to synthetic oil.
>
As explained to me today, apparently there are 4 types of modulators
available.
>
- - Low quality non-altitude compensating modulators (like the one previous=
ly
installed to my coach). The body is about 1 1/2 inches in diameter and th=
e
vacumn hose connects on the end. Apparently this modulator is calibrated =
to
sea level. (I think our altitude in Edmonton is just over 2000 feet) =
>
- - Higher quality non-altitude compensating modulators. I don't have any
information to help differenciate from the one listed above. Apparently
this modulator is also calibrated to sea level.
>
- - altitude compensating modulator. The body diameter is much larger (more=
like 2 1/2 inches in diameter) and the vacumn hose attaches to the side o=
f
the body rather than the end. Apparently the altitude compensator is take=
n
care of with an internal bellows. (This is the one now installed in my
coach)
>
- - non-altitude compensating modulator in a large diameter body. Apparentl=
y
the most obvious difference between this and the altitude compensating
module is that this one is lighter (no altitude compensating bellows
inside.
>
Although I don't have any part numbers I hope that the above may be of so=
me
assistance should someone else experience transmission problems.
>
Gary Zingle
1973 GMC 26 foot
Enjoying another sunny Alberta day
p
at trouble shoot and repair while not extracting the maximum money.
>
After an extended test drive with the mechanic today he found that, as I
reported earlier, the shifts were inconsistent.
>
Further it was found that what was actually causing the high revs when
starting the coach moving was that the coach was starting out in 2nd gear=
.
>
On a couple of occasions during the test drive it even started out in hig=
h
gear!
>
I was told that the vacumn modulator and the govenor were suspects.
>
Once up on the lift the mechanic found that at some time in the past the
vacumn modulator had been replaced with a poor quality part.
>
The govenor was found to be O.K. (The only change to the govenor was to
install a different spring to satisfy my request that low throttle shifts=
occur at lower speeds.)
>
The oil was not burn't, nor were there signs that the oil had been change=
d
to hide burn't oil during the motorhome sales process (grime undisturbed =
at
pan to transmission connection)
>
With only the modulator change, the govenor spring change, oil and filter=
change the transmission now consistently starts out in 1st gear and on
light throttle will upshift to 2nd at about 22 mph and to 3rd at about 30=
mph. Much more as I expected it should be.
>
The engine is not forced to spin the convertor up nearly as high and the
torque convertor has a much easier time of it.
>
I was pleasantly surprized to find that the modulator could cause so many=
symptoms. The modulator did not show any physical signs of total failure
(no transmission oil found in the vacumn line).
>
The transmission still shifts extremely softly so I still want to add the=
shift kit at some time in the future (although when I do so I think I wil=
l
leave the govenor spring as it is). At the time I install the shift kit I=
will change over to synthetic oil.
>
As explained to me today, apparently there are 4 types of modulators
available.
>
- - Low quality non-altitude compensating modulators (like the one previous=
ly
installed to my coach). The body is about 1 1/2 inches in diameter and th=
e
vacumn hose connects on the end. Apparently this modulator is calibrated =
to
sea level. (I think our altitude in Edmonton is just over 2000 feet) =
>
- - Higher quality non-altitude compensating modulators. I don't have any
information to help differenciate from the one listed above. Apparently
this modulator is also calibrated to sea level.
>
- - altitude compensating modulator. The body diameter is much larger (more=
like 2 1/2 inches in diameter) and the vacumn hose attaches to the side o=
f
the body rather than the end. Apparently the altitude compensator is take=
n
care of with an internal bellows. (This is the one now installed in my
coach)
>
- - non-altitude compensating modulator in a large diameter body. Apparentl=
y
the most obvious difference between this and the altitude compensating
module is that this one is lighter (no altitude compensating bellows
inside.
>
Although I don't have any part numbers I hope that the above may be of so=
me
assistance should someone else experience transmission problems.
>
Gary Zingle
1973 GMC 26 foot
Enjoying another sunny Alberta day
