This weekend was my first opportunity to put any miles on my recently
purchased 1973 GMC 26 foot coach.
>
Everything went better than I believed I could have hoped for on my first=
shake down run.
>
Before purchasing the coach I was convinced that a transmission overhaul
would be the first order of business, now I am not so sure.
>
I puchased from a dealer and have been unable to unearth any history for
the coach. ( i.e. previous service or shift kit situation) Although I fee=
l
confident that the 79,000 miles on the clock is real since the lower ball=
joints are original (need replacing soon though)
>
Although I only put on 50 miles at a time this weekend, the temperatures
were quite high (thermometer outside drivers window indicating mid 80s (F=
)
during the drive. My previous experience with tired transmissions has bee=
n
that they work less well when heated. No sign of that this weekend. Shift=
s
did not give trouble with heat.
>
1) - Now that I have put over a hundred miles on, the shifts seem
to be getting more consistent, although still soft and at fairly high
speeds. First to second will not occur lower than 30 mph and even
then only after the go peddle has been seriously relaxed. Same
thing with second to third but not before 45 mph.
>
Is it possible that the coach was sitting long enough that circulating so=
me
fluid through the trans has softened some seals etc. and done some good
things?
>
Although rpms are not high at those speeds I expected low throttle
shifts to have occurred earlier. Would shifts as described above be
considered normal for this unit?
>
2) The coach does not begin to move until the motor spins up pretty good.=
Initially I believed the transmission was slipping but now I am not sure.=
Reminds me of my old racing days with high stall torque converters, howev=
er
unlike those converters this one seems to lock up pretty good once it get=
s
going.
>
Although it is sluggish to get rolling it was willing to spin the wheels
when I was testing my emergency brake adjustment in my gravel driveway. (=
By
the way the wheels are free, no brakes dragging etc.)
>
All my heavy vehicle experience from the past was based on units with a
much shorter (more rpm for less mph) gear than the 3.07 I expect is still=
in this coach.
>
Is it normal for these coaches with the 3.07 gear and 16 and 1/2 inch
rubber to work the converter this hard in starts from a dead stop?
>
At this point I am contemplating:
A) - servicing the transmission ( clean out the pan, change the filter an=
d
fresh oil). Does any one make a 100 % synthetic transmission fluid? Anyon=
e
out there used synthetic?
>
B) - Adding more cooling capacity (I have always been of the opinion that=
as long as the transmission oil travels through the cooler in the radiato=
r
last before returning to the transmission it would be almost impossible t=
o
have too much transmission cooling)
>
C) - Add an external filter and temp gauge (probably in the hot oil exiti=
ng
the transmission)
>
D) Adding a transmission shift kit. Something with firm shifts but at low=
rpms unless the go peddle is pushed. (I can create downshifts anytime wit=
h
the downshift button recently added) Any suggestions for a trans shift ki=
t
to accomplish the above?
>
Any thoughts? Ideas? Opinions? Anything else I should do? Modulator?
Thoughts on transmission oils Synthetic, blended, other?
>
Any help would be appreciated.
>
Gary Zingle
1973 GMC 26'
>
Just enjoying another day in Sunny Alberta
purchased 1973 GMC 26 foot coach.
>
Everything went better than I believed I could have hoped for on my first=
shake down run.
>
Before purchasing the coach I was convinced that a transmission overhaul
would be the first order of business, now I am not so sure.
>
I puchased from a dealer and have been unable to unearth any history for
the coach. ( i.e. previous service or shift kit situation) Although I fee=
l
confident that the 79,000 miles on the clock is real since the lower ball=
joints are original (need replacing soon though)
>
Although I only put on 50 miles at a time this weekend, the temperatures
were quite high (thermometer outside drivers window indicating mid 80s (F=
)
during the drive. My previous experience with tired transmissions has bee=
n
that they work less well when heated. No sign of that this weekend. Shift=
s
did not give trouble with heat.
>
1) - Now that I have put over a hundred miles on, the shifts seem
to be getting more consistent, although still soft and at fairly high
speeds. First to second will not occur lower than 30 mph and even
then only after the go peddle has been seriously relaxed. Same
thing with second to third but not before 45 mph.
>
Is it possible that the coach was sitting long enough that circulating so=
me
fluid through the trans has softened some seals etc. and done some good
things?
>
Although rpms are not high at those speeds I expected low throttle
shifts to have occurred earlier. Would shifts as described above be
considered normal for this unit?
>
2) The coach does not begin to move until the motor spins up pretty good.=
Initially I believed the transmission was slipping but now I am not sure.=
Reminds me of my old racing days with high stall torque converters, howev=
er
unlike those converters this one seems to lock up pretty good once it get=
s
going.
>
Although it is sluggish to get rolling it was willing to spin the wheels
when I was testing my emergency brake adjustment in my gravel driveway. (=
By
the way the wheels are free, no brakes dragging etc.)
>
All my heavy vehicle experience from the past was based on units with a
much shorter (more rpm for less mph) gear than the 3.07 I expect is still=
in this coach.
>
Is it normal for these coaches with the 3.07 gear and 16 and 1/2 inch
rubber to work the converter this hard in starts from a dead stop?
>
At this point I am contemplating:
A) - servicing the transmission ( clean out the pan, change the filter an=
d
fresh oil). Does any one make a 100 % synthetic transmission fluid? Anyon=
e
out there used synthetic?
>
B) - Adding more cooling capacity (I have always been of the opinion that=
as long as the transmission oil travels through the cooler in the radiato=
r
last before returning to the transmission it would be almost impossible t=
o
have too much transmission cooling)
>
C) - Add an external filter and temp gauge (probably in the hot oil exiti=
ng
the transmission)
>
D) Adding a transmission shift kit. Something with firm shifts but at low=
rpms unless the go peddle is pushed. (I can create downshifts anytime wit=
h
the downshift button recently added) Any suggestions for a trans shift ki=
t
to accomplish the above?
>
Any thoughts? Ideas? Opinions? Anything else I should do? Modulator?
Thoughts on transmission oils Synthetic, blended, other?
>
Any help would be appreciated.
>
Gary Zingle
1973 GMC 26'
>
Just enjoying another day in Sunny Alberta
