Vacuum pump and VRV
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Tuned
Joined: Aug 2002
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From: Greatest state on earth
Vacuum pump and VRV
I dont have a decent manual for my 1986 truck yet, so needing some info. How much vacuum should the pump produce at idle? I just rebuilt the C6 transmission and trying to confirm the vacuum supplied to modulator valve is correct. The VRV is not seeing the numbers it should from information I have found. I cant get to 15" of vacuum at idle and then drop to 5" at full throttle. The pump produces right at 20" at idle and maintains a little higher with increased rpm.
Are there some diagnostics I can do to confirm if air pump or vrv is bad?
Are there some diagnostics I can do to confirm if air pump or vrv is bad?
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Tuned
Joined: Aug 2002
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From: Greatest state on earth
As I have been reading over different texts about adjusting, there seems to be a bit of conflicting information. It also makes me think the VRV may be the problem. I am going to remove it and see if can be popped apart and maybe replace any internal components that could cause a problem.
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Tuned
Joined: Aug 2002
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From: Greatest state on earth
Over the last hour I went ahead and removed the VRV from truck and was disassembled. Not much to what there. It was cleaned up best I could. I noticed before it would not really hold a vacuum. Just leak down slowly. It will now at least will maintain the vacuum draw I put on it. There is a very fine line between holding a vacuum and dropping off fairly quickly. From what I understand I need to adjust to hold a specific vacuum at idle then it opens and drops down very low at full throttle. There does not seem to be much modulation between holding a vacuum and dropping to nothing. But this is just a static bench test. Tomorrow I will install and this time follow the text in an ATSG manual to set it. It seems to make some sense but time will tell. If I can get it to maintain close to the specified vacuum at idle without being cranked over to max adjustment, it may fall within range now at full throttle. Hoping anyway.
i ain't rite
Joined: Mar 2005
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From: Marlboro Mental Hospital.
the higher the vacuum the better. a new pump should hold 21 inches.
you need at least 18 inches for the trans to work properly.
and vacuum is measured at idle, not with engine reved.
you need at least 18 inches for the trans to work properly.
and vacuum is measured at idle, not with engine reved.
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Tuned
Joined: Aug 2002
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From: Greatest state on earth
I was following the information with a Transgo spring kit for the C6. It suggests adjusting the vrv to maintain 14-17" at idle and then drop to less than 5" at full throttle. I have not been able to get it to hold anything more than 10" at idle and little difference at any other position. Now it will hold 20" and not bleed off without much spring load. But this is just a bench test. I can only hope to something close when installed.
I just finished installing and adjusted everything. The air pump is pulling 22" solid at idle. It was leaking at the rubber boot that has both lines connected.
I can only get 10-12" output max. It does drop to 5 when throttle is open. I guess another vrv is in the equation. But who has them?
I just finished installing and adjusted everything. The air pump is pulling 22" solid at idle. It was leaking at the rubber boot that has both lines connected.
I can only get 10-12" output max. It does drop to 5 when throttle is open. I guess another vrv is in the equation. But who has them?
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