Transmission modulator

[tom geiger]

Ok, so kinda want to replace the transmission modulator after cleaning the tube and replacing the hoses. What would be the part number and also does
taking the old one out cause transmission fluid to drain out?

Thanks,
Tom
76 Eleganza 2
Kansas City, Mo

 

[wrightjohn 2646]

Tom,
Why do you want to replace the present installed modulator? Does it still work and transmission shift correctly?

Yes, you will leak fluid out of the modulator port if the transmission has been sitting for a period of time, this is called leak down from the converter and happen quickly or over an undetermined period of time. It is normal! It is also a good way to check if you have the correct level of transmission fluid and to know what the level means on your dip stick. The way to check the level is to remove the modulator IMMEDIATE after SHUTTING DOWN the engine and see if fluid will come out the port or no fluid comes out the port. Fluid coming out means level too high and no fluid means fluid level is OK or actually a little bit low and you could add

As for a part number if you absolutely must put a new modulator in.

AutoZone: Part# MV105

I have used this one and it works just fine

RockAuto list several and you can use these numbers to find a modulator at other parts store. I always use 1975 Oldsmobile Tornado 455 eng as a search string.

Fram FM2331
AC Delco 89057785
Airtex/Wells 7R1003
Standard Motor Products TM15

Most come with an instruction sheet on how to adjust the shift points.

http://www.gmcmhphotos.com/photos/transmission-install/p26806-img-0716.html

JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan

>
> Ok, so kinda want to replace the transmission modulator after cleaning the tube and replacing the hoses. What would be the part number and also does
> taking the old one out cause transmission fluid to drain out?
>
> Thanks,
> Tom
> 76 Eleganza 2
> Kansas City, Mo
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[charles boyd]

Sir, if your modulator is OEM it is long, big and inlet is on the side. Replacements are short, small and inlet is in the end. I usually eyeball the
line and use a small tubing bender and bend the tube 90* to fit straight in the end. The pointy end of the line goes inside the modulator for
stability and rubber hose seals it.

> Ok, so kinda want to replace the transmission modulator after cleaning the tube and replacing the hoses. What would be the part number and also
> does taking the old one out cause transmission fluid to drain out?
>
> Thanks,
> Tom
> 76 Eleganza 2
> Kansas City, Mo

--
C. Boyd
76 Crestmont
East Tennessee

 

[tom geiger]

Well, will hope not to have to replace it but am having shifting idsues once it heats up. Will clean everything down and keep my fingers crossed it
does the job. But if not, next is the modulator.

 

[wrightjohn 2646]

Tom,
Are you still using the original metal line that run down to the modulator? The line has a factory pinch in it to act as a restrictor to smooth the vacuum out. It is common to have the interior cruded up and maybe plugged. Rinse it out with a good carb cleaner and blow out with air to insure that it is clean. Most if not all of the replacement modulators that I have list come with a rubber 90 degree hose to easy the hookup.

JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan

>
> Well, will hope not to have to replace it but am having shifting idsues once it heats up. Will clean everything down and keep my fingers crossed it
> does the job. But if not, next is the modulator.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[tom geiger]

Hey JR, I not absolutely sure on if it has the original metal tube, it appears it is. I'll try cleaning it out and air blowing it out to unclog it.
Let u guys know how it goes.
Thanks
Tom