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built 4l80 is slipping 2nd suddenly

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Old 06-15-2014, 03:23 PM
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Default built 4l80 is slipping 2nd suddenly

So basically its built with a Jakes L2 kit with the addition of billet input and forward hub. 2nd gear is slipping under heavy load. Light loads is decent and reports 1.48 ratio, when it slips ratio goes to 1.80-2.0 (have a pid to divide unit by output)This happened suddenly. Fluid doesn't appear burnt... still need to drop the pan.

Local track sucks and I'm always blowing the tires off on the 1-2 shift so I'm wondering if this is shocking the sprag and its broken now. Just throwing that out there.. making 750-800rwhp.

Just looking for ideas on what would cause 2nd to slip. 1st and 3rd do not show slip at all.
Old 06-15-2014, 03:27 PM
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I have plans to pressure test as well
Old 06-15-2014, 06:11 PM
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I know this is a stupid question, but are you 100% sure the fluid level is okay?

Are you using a tranny cooler? One with a fan?

I wouldn't rule out broken sprag, but its a little uncommon even at that power level. It sounds like the frictions are probably toast. It could also be a bad seal on the direct piston or center support.
Old 06-15-2014, 06:26 PM
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Fluid level is good. Trans has maybe 1500 miles and has never slipped before at the track.I monitor every time I go. Trans cooler is mounted on stock radiator with stock fans. It stays cool unless you hot lap back to back to back. I have had it hot but changed the fluid. Friction's could be gone I'd hope not though haha. Being so sudden I was thinking either sprag or hydro's
Old 06-16-2014, 09:36 AM
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any ideas from anyone else or things i should do or test before i remove the trans?
Old 06-16-2014, 01:10 PM
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Why not ask Jake directly, or send him a PM on here directing him to this thread? If anyone has an idea it'll be him

Btw, you aren't blowing through the converter are you?



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