73-87 Chevy _ GMC Trucks > Engine/Drivetrain

TH400 Dragging in 3

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Big Dee:
85 silverado c30 with 454 and th400 seems to be holding back in high gear. shifting into neutral at 40 mph she frees up. back into 3 seems like 2. mileage is very bad. fliud and filter is new. original trans with 125K miles. could sure use some help diagnosing. :-\

JohnnyPopper:
Are you sure it's the tranny and not the motor choking?

When you drop into 2nd what does it do?

It's just a dumb animal waiting for torque from your big mama 454.

What type of fuel delivery system does she have?

Big Dee:
JP, running an edelbrock 1400 because the 100K thermoquad looks complicated. hindsight what it is, that was the wrong decision. however i have improved at tuning eddies. 
Downshifting to second at 20 mph revs up and holds back. typical of a downshift but look at the speed.
4.10 gears / 265/75 tires.
Choking motor?

JohnnyPopper:

--- Quote from: Big Dee on April 09, 2022, 11:05:36 AM ---JP, running an edelbrock 1400 because the 100K thermoquad looks complicated. hindsight what it is, that was the wrong decision. however i have improved at tuning eddies. 
Downshifting to second at 20 mph revs up and holds back. typical of a downshift but look at the speed.
4.10 gears / 265/75 tires.
Choking motor?

--- End quote ---

Not enough information  :-[ Please define 'holding back' in 3rd gear.

You said you go into N and drop back in at 40, seems to free up. What does that mean?

Maybe a video?

Big Dee:
JP,
when coasting in neutral around 40 mph. then shifting to Drive, slows down like the brakes are on. engine revs up until reaching 30 mph then cruises good. :-\
Feels like driving around in second but counting all 3 shifts.

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