Still not consistently shifting from first to second

[RF_Burns]

Follow-up to my shifting issue.

I replaced the modulator with a new unit, a Rostra 44160. The existing modulator (new with the rebuilt transmission in 2010) had a black and red
stripe, the new one had only a red stripe. Sorry I don't recall what the difference in the colour stripes are, but I believe the Black/Red has more
range of adjustment.

I replaced the OEM tube to the modulator with a piece of Poly-Armor tubing. I used 3/16" (I believe) as it's OD closely matched the OD of the new
modulator vacuum inlet (0.300"). There is no restrictor in the new line.

This past weekend we drove to a GMC Heritage Cruisers rally in Peterborough Ont about 4 hours away. We did about 1 hour of driving on county roads
with frequent stops and the transmission shifted perfectly each time. WOO HOOO!

BTW, I checked the cost of a new modulator at NAPA and was quoted ~ $100 CDN. This modulator was in-stock at a transmission shop at a cost of ~
$35.00CDN

--
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

 

[johnny]

Kelly - or somebody - how do you get the modulator apart? It doesn't look like the weight ass'y will clear the metal dome. Or do you just pull the
housing off the plunger after removing the gear and leave the weight ass'y alone?

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[Jim Hupy]

The modulator is a vacuum dashpot that goes into the side of the
transmission case about at the level of the fluid in the pan. It only
contains a plunger attached to a vacuum diaphram and an adjustable spring.
Johnny, I think you might be confusing it with the governor, which is a
complex device that is gear driven, has flyweight assembly along with a
speedometer drive gear. It is located on the drivers side of the
transmission below the exhaust manifold of the engine.
Jim Hupy
Salem, OR
78 GMC Royale 403

On Wed, Sep 19, 2018 at 9:35 AM Johnny Bridges via Gmclist <

> Kelly - or somebody - how do you get the modulator apart? It doesn't look
> like the weight ass'y will clear the metal dome. Or do you just pull the
> housing off the plunger after removing the gear and leave the weight ass'y
> alone?
>
> --johnny
> --
> 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me
> in hell" - ol Andy, paraphrased
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[charles boyd]

Johnny, I believe you have to do some grinding to get the dome off the governor?

http://www.gmcmhphotos.com/photos/search.php?searchid=346031

> Kelly - or somebody - how do you get the modulator apart? It doesn't look like the weight ass'y will clear the metal dome. Or do you just pull
> the housing off the plunger after removing the gear and leave the weight ass'y alone?
>
> --johnny

--
C. Boyd
76 Crestmont
East Tennessee

 

[powwerjon]

Why would you want to take the top off the governor. There are no user serviceable part inside. If the piston that moves up and down to change the ports is working then you don’t need to touch it. The governor for the GMC TH 425 transmission is special and the regular governor does not work as well. If you have headers then having the top cover removable then you can just get it out to clear the headers. Jim K sells reprogrammed units.

http://www.appliedgmc.com/prod.itml/icOid/1024

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 30’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan

>
> Johnny, I believe you have to do some grinding to get the dome off the governor?
>
> http://www.gmcmhphotos.com/photos/search.php?searchid=346031
>
>

>> Kelly - or somebody - how do you get the modulator apart? It doesn't look like the weight ass'y will clear the metal dome. Or do you just pull
>> the housing off the plunger after removing the gear and leave the weight ass'y alone?
>>
>> --johnny
>