What causes a transmission to slip?...
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TECH Apprentice
Joined: May 2006
Posts: 308
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From: Nebraska
What causes a transmission to slip?... I have a re-occurring issue with my 4L60E where it "slips" during WOT. Basically, it disengages at approx 4000 rpms (in 2nd gear) and the rpms spike up briefly to 5000+, and then returns back before shifting into 3rd. What is the cause of this?....I have a vac mod controlling the line pressure...
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From: Az
The vacuum modulator is designed to give you max pressure when you have low vacuum such as manifold vacuum under heavy throttle. The brake cylinder or booster will act as a reservior and hold the vacuum high causing low pressure during shifts. Finding a different vacuum source will depend on your intake your are running.
It is also possible its not a slip at all , Since the band is released during the 2-3 shift it could be a matter of hydraulic timing. There could be too much fluid going to release the servo to fast and basically if this happens and the band is released to soon before the 3-4 clutch can apply you will in fact go momentarily back to first, Which would feel like neutral or a slip followed by third.
Did you install the shift kit your self its possible that a wrong hole could have been enlarged in the spacer plate and what servo are you using ?
Did you install the shift kit your self its possible that a wrong hole could have been enlarged in the spacer plate and what servo are you using ?
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TECH Apprentice
Joined: May 2006
Posts: 308
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From: Nebraska
sounds like I need to change my vac mod tap. Performabuilt your description of what's happening is spot-on.... I'm not sure what servo is in it (it's an aftermarket trans)...is the shift kit something I could easily check out and/or replace myself?...
Well for that issue I would consider changing the transfer plate, However you really need to know whats in it to fix it shift kit wise,
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The vacuum modulator is designed to give you max pressure when you have low vacuum such as manifold vacuum under heavy throttle. The brake cylinder or booster will act as a reservior and hold the vacuum high causing low pressure during shifts. Finding a different vacuum source will depend on your intake your are running.
How does it work for a boosted car?
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On The Tree
Joined: Jun 2007
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From: haltom city/DFW, Texas
The brake booster has a check valve . It will not trap vacuum in the line , it will keepit in the booster ! Trans-go makes a valve for turbo/ boosted setups . The problem you describe sounds like a shift timing/tune issue .
