Violent gear changes in my auto '67 Mustang

[Missy701]

Me again.

I've noticed that gear changes are very violent, the car launches forward really hard and the faster I drive the worse it is, would tightening the bands stop this or is it just a characteristic of the Mustang?

[yellowgriff]

check the fluid level in the box

[Missy701]

It has been checked and is fine.

[LuS1fer]

Are you registered on www.mocgb.net? You'll find a lot more knowledge over there.

[Fartgalen]

Is the gearbox fluid fresh ?

[Missy701]

LuS1fer said:

Are you registered on www.mocgb.net? You'll find a lot more knowledge over there.

Yes I am, can't seem to get on there at the moment though, will keep trying. Cheers.

[Missy701]

Fartgalen said:

Is the gearbox fluid fresh ?

I have no idea, but it's at least a couple of years old.

[Missy701]

[AdeTuono]

Has it always done it, or is a recent problem? Maybe a previous owner installed shift kit?

[Missy701]

Yes it has always done it, I don't know if there is a shift kit on it, but I don't think so. It's a bit alarming It seems to take ages for it to change gear and when it does it does a kind of violent lurch forward as it does. Maybe that is just how it is and I'll have to get used to it. Maybe tightening the bands might help, I guess its worth a try.

[LuS1fer]

Sorry if this is obvious but you know you have to check the gearbox oil level with the car running and the shifter in Park to get the level right? I found out the hard way....

[The Wookie]

Not sure how the Mustang system works, but I know you can get similar symptoms in 928's if the vacuum line is leaking or has come off.

The 'box uses plenum pressure to determine how much you're booting it, atmospheric pressure indicates wide open throttle and the shifts are pushed up in the rev range and are more abrupt to prevent slippage and such.

If the line has come off, the pressure is always atmospheric and the box 'thinks' it's WOT all the time, leading to reluctant shift selection and violent shifts.