tranny modulator line

[skip hartline]

Evening all,

Been looking over the archives on modulators but in reading between the lines it appears to me that if the restrictor was removed the tranny wouldn't
really care. I prefer to keep all the steel I can because of the heat in the downhill run. Any thoughts on this. I'm getting an occasional hard and
late shifts like sometimes the vacumn isn't right. It will actually sometimes chirp the tires from 1st to 2nd and real late on 2nd to 3rd.

Skip Hartline
--
74 Canyon Lands, FiTech,
3.7 FD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd

 

[jim kanomata1]

Manny T can answer that.
He might be on a tour.

On Tue, Jun 11, 2019 at 5:42 PM Skip Hartline via Gmclist <

> Evening all,
>
> Been looking over the archives on modulators but in reading between the
> lines it appears to me that if the restrictor was removed the tranny
> wouldn't
> really care. I prefer to keep all the steel I can because of the heat in
> the downhill run. Any thoughts on this. I'm getting an occasional hard and
> late shifts like sometimes the vacumn isn't right. It will actually
> sometimes chirp the tires from 1st to 2nd and real late on 2nd to 3rd.
>
> Skip Hartline
> --
> 74 Canyon Lands, FiTech,
> 3.7 FD, Manny Tranny,
> Springfield Distributor,
> 2001 Chevy Tracker Ragtop Towd
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[john r. lebetski]

Disconnect the steel and flush both ways with carb cleaner and air. Make sure you can blow both ways. Then drive on road test. There may be internal
scale getting into the orifice This will help prove disprove the theory. If it works maybe coat the inside with something more lasting than WD-40
like a light oil film you put in and blow out.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[RF_Burns]

I was having 1-2 upshift issues last summer. Using a hand vacuum pump I found and intermittent leak on the hose connection to the modulator. Current
replacement modulators use a hose larger than the OEM steel tube. I had pushed the tube over the stop bump in order for it to seal. This had worked
fine, but now I was getting intermittent shifting when hot. Using the vacuum pump I found that slightly moving the tube caused a leak.

I bent up a new larger tube to match the new modulator tube so the hose will fit snug. I have had no shifting issues since. I have noticed that
previously I could not even feel the tranny shift, now I can but its not a hard shift, more like I feel on my pickups.

The new tube does not have a restriction. I thought about making one in the new tube, but have not done so yet. I'm also interested in feedback about
this issue.

Thanks
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

 

[jim kanomata1]

There is a reason why the factory used a steel line there.
They know more than us as they deal with it and if all rubber is better,
they would have done that.

On Wed, Jun 12, 2019 at 8:02 AM Bruce Hislop via Gmclist <

> I was having 1-2 upshift issues last summer. Using a hand vacuum pump I
> found and intermittent leak on the hose connection to the modulator.
> Current
> replacement modulators use a hose larger than the OEM steel tube. I had
> pushed the tube over the stop bump in order for it to seal. This had worked
> fine, but now I was getting intermittent shifting when hot. Using the
> vacuum pump I found that slightly moving the tube caused a leak.
>
> I bent up a new larger tube to match the new modulator tube so the hose
> will fit snug. I have had no shifting issues since. I have noticed that
> previously I could not even feel the tranny shift, now I can but its not a
> hard shift, more like I feel on my pickups.
>
> The new tube does not have a restriction. I thought about making one in
> the new tube, but have not done so yet. I'm also interested in feedback
> about
> this issue.
>
> Thanks
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[Ken B]

Why remove it? It has worked well on many thousands of vehicles.

Mine got plugged up about 15 years ago. I removed it and tried to blow shop air through it. Nothing. Soaking / filling it with carb cleaner and
several other things would not clear it up. So I hooked up 100 PSI shop air to it on the bottom end and started heating it on the restrictor end
until it got to a dull red on the first 3 or 4 inches. The restriction cleared. I then ran liquid anti-seize through it to coat the inside. It has
run fine for 15 years or so since that "repair". I believe the restriction was carbon and not rust. It took less than 3 minutes of heat to clear it.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[john r. lebetski]

A couple more things. I fixed one with delayed upshift where the hose had aged and chafed through, but not on the actual ends of the steel run. It
was a 2" section wher it T'ed off so not obvious, but same vacuum circuit.
The hard pipe should be hand aligned to the modulator as best as possible and use the shortest possible hose for the cleanest setup. After my new
engine install from Cinnabar that hose was a little too long and in an S sweep to make the connections. Under vacuum it would suck flat in the S
curves and pinch off most of the vacuum. I was getting delayed hard shifts. 60 seconds in a restaurant parking lot in Bowling Green Ky with a cutters
to shorten the rubber and hand bent the tube and been fine for 10+ years.
Lastly there are different SAE specs of vacuum hose. I don't have the chart handy but GM speced all that stuff to great detail. Like a few pages of
.pdf to describe each one. Some of the thinner wall washer type may not have the needed wall rigidity.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[skip hartline]

I really appreciate all the ideals, suggestions and experiences

Skip Hartline
--
74 Canyon Lands, FiTech,
3.7 FD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd