Neutralling transmission

[oldtimer]

This might sound like a stupid question, but:

On the installation and instruction sheet for my Hipster trans brake, it says in big bold letters : DO NOT NEUTRAL THIS OR ANY 3 SPEED TRANS .... THEY WILL EXPLODE !!
Can someone explain what " to neutral " a tranny means in the text that this phrase is used ??

Thanks,

George

 

[JDSfastGN]

im assuming they just mean neutral dropping the tranny. Revving up the motor in neutral and then slamming it into gear. Pretty violent and can definitly cause some damage

 

[blackplague]

What they mean is

DO NOT PLACE THE TRANS IN NEUTRAL AFTER THE RUN {either 1/8 or 1/4 miles} IS OVER!!!! I can not put enough emphasis on this. What happens if you do you? You risk the trans overspeeding internally { the direct drum} and the drum comming apart, thru the case,thru the floor pan, and into the driver. You may get away with it a few times, but you run the risk. I don't mean to yell, but i don't want anything to happen to you guys out there.

 

[TType84]

DO NOT PLACE THE TRANS IN NEUTRAL AFTER THE RUN {either 1/8 or 1/4 miles} IS OVER!!!! I can not put enough emphasis on this. What happens if you do you? You risk the trans overspeeding internally { the direct drum} and the drum comming apart, thru the case,thru the floor pan, and into the driver. You may get away with it a few times, but you run the risk. I don't mean to yell, but i don't want anything to happen to you guys out there.

really? why is that? even if you let off the throttle before popping it into neutral?

just curious`

 

[terrible-T]

WOOPS I do this all the time I call it LIFT AND DRIFT :redface:

 

[tom robison]

i had a th400 come apart about 12 years ago when put in neutral after a 1/4 mile pass. i learned my lessen!

 

[jakeshoe]

blackplaque is absolutely correct.

When you shift a TH350, 400, or other 3 speed into neutral while the vehicle is in motion, the direct drum no longer drives the planets. The planets begin to drive the drum after the clutches release.

The gear reduction effect of the planets to the output shaft get reversed, and the planets become an overdrive unit, the output shaft becomes the input to the planets, the direct drum the overdriven part on the (now) output side of the planets.

It causes the drum to rpm VERY high and can very likely cause it to centrifugally explode. Very similar to a flywheel coming apart in a manual trans application.

Did ya'll get that?

 

[Ssmnt408]

holy cow! I've never heard of that before, I've always done that at the end of the track.........yikes. Looks like I lucked out, Thanks for the info on that one and I sure won't be doing that agian!

 

[chris718]

shifting to neutral causes the drive shaft to become the input member instead of the input shaft and this changes applied load to geartrain and drum causing the direct drum to freewheel and overspeed beyond its burst speed.

 

[oldtimer]

Thanks guys for all your input. Although I didn't know for sure what was meant by neutralling the tranny, I suspected that putting it in neutral at the end of a run was what it meant.

The reason I was wondering, was that with my new combination, I was concerned about reading the plugs accurately at the end of run.
During my 4 speed days ( way in the past ) I used to put the car in neutral, shut off the engine and pull over on the return road and pull the plugs for reading.

Honestly, I had no idea about the potential danger in doing this in a 3 speed automatic

I'm sure glad I asked. Can you imagine the disaster at 150 MPH if the tranny exploded.

I sure appreciate the expertise and experience on this board

Thanks again,

George