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Discussion Starter · #1 · (Edited)
I have a full manual 4L80E with transbrake and fixed line pressure. The trans works great on the street. However, at the track, I'm having an issue with the 1-2 shift taking too long.

I can literally let go of the transbrake at 4500 rpm and instantly click the shifter into 2nd gear. The car will accelerate and hit the 7800 rpm rev limiter before the trans shifts.

I have datalogged trans pressure and it is around 205-210 until the release of the transbrake. Within a half of a second, it drops down to 100 psi and then recovers and starts to come back up and hits 200+ at around 3 1/2 seconds.

Is this a problem in the trans itself or is it something like needing a deeper trans pan to keep the fluid in it on hard acceleration?

Some details: 60' times in the low 1.3's at 3850 lbs, twin turbo engine on a radial, trans has: TCI billet input, steel forward drum, 36 element sprag and aluminum drum, new clutches last summer, new transbrake valve body, JD Hygard low viscosity, fluid level is correct at the pan rail, has PTC 9.5" single disc lockup converter which was fresh last summer. This trans has always taken around 2 seconds to shift from 1st to 2nd gear at WOT regardless of valve body manufacturer, regardless of builder.

Any help would be greatly appreciated.

Datalog can be seen at:
https://www.flickr.com/photos/[email protected]/

Trans pressure is downward pointing triangles. RPM is circles, driveshaft speed is upward pointing triangles
 

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Discussion Starter · #4 ·
Thank you both for your help. I'm hoping this is what it is. The trans works great on the street and the pressure is steady and constant. Obviously, there is no WOT in first gear on the street but everything seems to be good.

Hopefully it's just a low fluid issue.
 
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