Last Tuesday nite I finally got the E-Street EFI to communicate with the ECU and she fired right up. The calibration procedures went fine and the idle smooth as silk.

It's a 2WD long bed with a two-piece driveshaft but the rear shaft is out (and sitting on my living room coffee table) because I still need to finalize the exhaust system. The coupling shaft is installed to prevent the tranny lube from leaking out.... Today I fired it up and noticed the output shaft spins even when the transmission (a Tremec 5-speed) is in neutral. Is this "normal"?

I did some research and found sites which discuss viscous drag since the input shaft is turning and "In neutral, the transmission acts something like a torque converter--the input gears turn the oil and the oil turns the output gears. The effect is most noticeable when the transmission is cold and the oil stiff."

I've wrenched for years and have never encountered this. What say ye? Parasitic drag or something else?

 

does it spin free when the engine is off? sounds weird to me. That Tremec trans has the shifter going into the top yes? not likely to be linkage slightly out of whack if so...

 

2x.. yeah, it's weird to me too. It's my first ever truck with a two-piece shaft.

Correct, shifter is a rail system through the top and yes, the coupling shaft turns freely with the engine off and the trans in neutral.

Is this normal for any manual trans?

 

Every trans ive ran without the driveshaft hooked up spun the output shaft when the engine was running and trans in neutral, there is nothing wrong with the trans, its just the internal drag in the trans doing it. If you grabbed the output yoke it would stop

 

+1. My nv4500 spun up pretty good when I was breaking in my cam with no drive shaft in. As soon as you would touch the output shaft it would slow and stop. Completely normal.

 

Thanks fellas. My trepidation and angst has faded...

The collective knowledge base in this here forum is amazing.

 

Don't forget that the input shaft of the tranny is riding in the pilot bushing in the back of the crankshaft as it spins at idle, that is going to provide some rotation just through friction.

 

all gear boxes do this.

when my floor pan was out, you could see the front driveshaft spin a bit even with the hubs disengaged and t-case in 2wd.

'tis normal

 

Internal drag and normal.....

 

+1 my C4 did the same thing. Without any resistance from the driveline, axle, wheels, etc. there's nothing to stop the shaft from spinning, so the smallest rotational force from internal friction will spin it.

 

Yup, that's right.

D