Author Topic: vacuum gauge drops when put into drive?  (Read 1318 times)

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Offline eagle87

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vacuum gauge drops when put into drive?
« on: June 02, 2013, 11:29:41 AM »
ok, so at an idle my eagle has the vacuum guage reading at half way, however when its put into drive it drops one increment on the guage, is this normal? if not any ideas what is causing this? car is completely stock, new vacuum lines, working carter carb, new carb gasket, idles at about 600 in drive
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Offline vangremlin

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Re: vacuum gauge drops when put into drive?
« Reply #1 on: June 02, 2013, 11:51:55 AM »
I believe that's normal.  Mine experiences a similar drop.
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Offline profeagle

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Re: vacuum gauge drops when put into drive?
« Reply #2 on: June 02, 2013, 01:36:17 PM »
Yes, quite normal.  ;D

Offline SpreadEagle

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Re: vacuum gauge drops when put into drive?
« Reply #3 on: June 02, 2013, 01:40:05 PM »
Very normal. Not sure mine drops a whole Notch but Mine is a manual. But with a load on the motor normal.

Offline eagleman

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Re: vacuum gauge drops when put into drive?
« Reply #4 on: June 02, 2013, 01:46:41 PM »
That is the way it should be and as you increase rpm's it will drop futher then return to about half way at idle. Should read around twenty or so at idle.
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Offline eagle87

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Re: vacuum gauge drops when put into drive?
« Reply #5 on: June 02, 2013, 02:23:20 PM »
ok mine reads 20 at idle unless in drive at idle then drops a notch, just was concerned it was a transmission actuator problem
2010 Ford Explorer (Red)
2004 Jeep Grand Cherokee Special Edition (Blue)
2002 JeepGrand Cherokee Overland Edition (Silver) Rolled
2001 Cadillac Deville (Silver) Blown Engine :(
1999 Jeep Grand Cherokee Ltd (Graphite) Parts Jeep
1998 GMC Safari (Blue)
1990 Mercury Sable (Red)
1987 Eagle Wagon (Beige)
1987 Eagle wagon (Silver)
1987 Eagle Wagon Limited (Brown)
1986 Eagle sedan (Blue)
1983 Eagle SX/4 Sport (Black)
1982 Concord DL (Maroon)
1968 Rebel Conv (Gold)

Offline carnuck

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Re: vacuum gauge drops when put into drive?
« Reply #6 on: June 02, 2013, 03:21:28 PM »
Nope. When you engage the transmission into gear the back pressure of the trans pump makes the motor slow down and results in the vacuum drop. When I put my Eagle in drive, the idle is so low you can barely feel the 727 engage due to a higher stall converter. Figured out I'm getting close to 20 mpg highway now though.
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'82 Eagle Wagon (Brown Betty) 4.2L/727/NP229 and soon 8.25 rear axle and non-vacuum 3.08 front to match. 235/75/15 tires. It's down to minor body work (someone creamed my driver's door but I have another in good shape) almost rust free and interior work (seats are worn and carpet torn). $2000 but about to go up due to more work being done.

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