Turbo 400 leak
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Joined: Aug 2017
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Turbo 400 leak
I have been chasing a leak on my '75 turbo 400. I even took to a tranny shop and they could not figure it out.
I finally traced it to the vacuum pod thingy. I fear if I remove it I will have lots of fluid draining out. Is there a gasket on this or is it an O ring ?
I finally traced it to the vacuum pod thingy. I fear if I remove it I will have lots of fluid draining out. Is there a gasket on this or is it an O ring ?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I don't believe a lot of fluid will come out of the vacuum modulator because its on the high side of the fluid level. Looking at Summit Racing part number B&M 20234, it does show a "O" Ring on the outside of the unit. They have a few units from $12-$30. The better ones come with a new hose and are adjustable, meaning you can change your shift points using a allen wrench. I have heard stories that sometimes the modulators leak internally and will introduce tranny fluid into the engine via intake vacuum.
Last edited by HeadsU.P.; Sep 9, 2017 at 08:20 AM.
Instructor
Joined: Nov 2014
Posts: 161
Likes: 17
From: Georgia
Try running it for a couple minutes in place and shifting into each gear before removing the modulator...not long enough to make it too hot to work on. That will help to get the fluid level in the pan down some. On my 73 the longer it sits the more fluid migrates to the pan area.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Changing the modulator, you might lose a half pint of ATF. Not much there. Modulator seals into the case with an o-ring. Remove the vacuum line, take out the 5/16 bolt (1/2" head) slide the clip off and pull. IF the valve sticks in the modulator (not very often) just slip it back into the case in the same direction I came out. Lube the o-ring with some grease or Vaseline, and put it on the modulator and stuff it back in.
Instructor
Joined: Nov 2013
Posts: 128
Likes: 29
From: Bloomfield Township Michigan
Check the dipstick tube at the transmission. This is also sealed by an o-ring. I had the same appearing leak and thought it was from the vacuum modulator but was actually from the tube seal and dripped to look as if it was coming from the modulator.
Jeff
Jeff
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Joined: Jan 2006
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From: Crossville TN
Transmission Controlled Spark [emissions] system. That 'system' needed to detect when in an upper transmission range (TSC defeated when in higher ranges). It was primarily for reducing emissions at idle and off-idle conditions.
P.S. If your vehicle had it and you don't "need" it (for state emissions requirements), you don't want it!
P.S. If your vehicle had it and you don't "need" it (for state emissions requirements), you don't want it!