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-   -   New PB, 4.8l 76/68 Magnum (https://www.performancetrucks.net/forums/drag-racing-139/new-pb-4-8l-76-68-magnum-548053/)

lycominghunter 02-26-2017 08:44 PM

New PB, 4.8l 76/68 Magnum
 
1 Attachment(s)
Got to the track today after changing from 12psi springs in the wastegate to 16.5psi springs on the Magnum 76/68. Pretty sure the turbo is maxxed out as it was dropping about 1.5psi in the upper RPM range. So, 17psi tapering to 15.5psi, AFRs were mid to high 10s, 15* timing through the mid range and 16* above 6000rpm.
Attachment 81944
On the ride home I had a pleasant whining coming from the trans/converter - so something is up which would explain 1) 2-3 shift taking forever, 2) 800rpm shift extension (usually 1200rpm) on the 2-3 shift, 3) and the trans shifting at a much higher rpm than usual (1-200rpm higher). Think the whining is the trans pump, but I'd think that if the trans was the culprit it'd be the clutches that would be slipping - I really don't know transmissions that well. Just hoping the converter is fine since I have more $$ in that then the trans. Trans is a stock 85k+ pull out with a shift kit.

Any way to determine from the data logs if the trans is slipping vice the converter? I unfortunately wasn't logging input/output shaft speeds.

fastjweb 02-26-2017 09:00 PM

Big Congrats Man!!, she sounded great

Vortec350ss 02-27-2017 09:47 AM

Awesome!

lycominghunter 02-27-2017 04:36 PM


Originally Posted by fastjweb (Post 5400123)
Big Congrats Man!!, she sounded great

Congrats to you too. If it weren't for your methanol tee fitting, I wouldn't have been able to race this past weekend. We'll be in the 9's in no time!


Originally Posted by Vortec350ss (Post 5400180)
Awesome!

Thanks Vortec!


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