Vacuum pump issues

ezgn

Well-known member
Steel Soldiers Supporter
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715
93
Location
Lake Elsinore Ca.
I checked the vacuum on the pump at the 3/8" fitting and it holds at a steady 26. At the small line going from the pump to the vacuum switch it flucuates rapidly from 18-14. Coming out of the vacuum modulator to the tranny is a steady 11. The truck is a 1986 M1008 shifts at 15 and 35. Any help would be appreciated. The lines are all new and tight.
 

Russm

Active member
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Location
Ft. Wainwright, AK
From your description I don't see any issues. I've adjusted mine to also shift at 15 and 35.
Are the shifts rough or causing concern somehow?

Sent from my LM-G710 using Tapatalk
 

ezgn

Well-known member
Steel Soldiers Supporter
438
715
93
Location
Lake Elsinore Ca.
From your description I don't see any issues. I've adjusted mine to also shift at 15 and 35.
Are the shifts rough or causing concern somehow?

Sent from my LM-G710 using Tapatalk
My concern is that it fluctuates rapidly between 18 and 14 and I was wanting to know if this was normal or a symptom of the vacuum pod getting weak. Thanks
 

cucvrus

Well-known member
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Location
Jonestown Pennsylvania
I agree with the previous poster. If it shifts fine and you have no negative problems keep on going. What is the concern? It will fluctuate it is on a distributor drive with a diaphragm. Finding new ones is getting hard. Are you having issues? If you dig deep enough you will find more problems. But if it were mine and everything was shifting fine I would drive on. That vacuum system works fairly easy. I usually get a local transmission shop to set mine up if I have issues with the shift and not shift. Works out better for me and is $20-$40. well spent. Good Luck.
 

ezgn

Well-known member
Steel Soldiers Supporter
438
715
93
Location
Lake Elsinore Ca.
I agree with the previous poster. If it shifts fine and you have no negative problems keep on going. What is the concern? It will fluctuate it is on a distributor drive with a diaphragm. Finding new ones is getting hard. Are you having issues? If you dig deep enough you will find more problems. But if it were mine and everything was shifting fine I would drive on. That vacuum system works fairly easy. I usually get a local transmission shop to set mine up if I have issues with the shift and not shift. Works out better for me and is $20-$40. wel
 

ezgn

Well-known member
Steel Soldiers Supporter
438
715
93
Location
Lake Elsinore Ca.
Thanks for the help. I didn't know that the vacuum pump readings fluctuates. I feel some relief. I know the pumps are getting scarce so I thought I should grab one for insurance.
 
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