Is it hard on my transmission to drive it with vaccuum line unhooked?

[pete29]

i was wondering if it is hard on a 350 tranny to drive it with the vaccuum line that goes from the tranny to the intake manifold. i know if shifts a little late with unhooked but i kind of like it unhooked to do this. does anyone know if this is bad for the tranny?

[bigdon-70blazer]

Could that keep it from shifting into the other gears?

[pete29]

Originally Posted by bigdon-70blazer

Could that keep it from shifting into the other gears?

i pretty sure it goes into all gears, just a little later

[vtblazer]

Vacuum line just goes to the shift module, can't imagine it would cause any harm but I'm not in the trasmission business either.

Call a local shop to be sure.

[Critter]

Originally Posted by vtblazer

Vacuum line just goes to the shift module, can't imagine it would cause any harm but I'm not in the trasmission business either.

Call a local shop to be sure.

I'm with VT as far as calling a shop goes! My *speculation* is that it could possibly wear out the clutches prematurely. Seams to me you are just asking for trouble if it isn't shifting firmly or at the correct time. Might not be anything to be concerned with, though.

[drunkbus]

Just buy an adjustable vacuum modulator and adjust your shift points wherever you want them. That way you don't have to worry.

[cparman]

If you want it to shift LATE, and HARD, you might try replacing the vacuum modulator, as DRUNKBUS suggests. Most aftermarket modulators will be adjustable. The adjustment is a straight slot screw in the inside of the tube where the vacuum line goes. If I remember right truning it in is late, and out is early. I personally do not recommend doing what you are doing. Trans guys help me. It is increasing the fluid pressure, and making the transmission hit hard on shifts. Doing this long term I would think will be hard on the trans. A shift kit installed in the valve body can do the smae and still make the trans shift at the proper MPH.

[Firebirdjones]

Without vacuum to the modulator you are increasing line pressure,,,just as it would do if the throttle was floored and there isn't any intake vacuum present.
I personally wouldn't do it though, you'll get later and harder shifts.

If later part throttle shifts are what you are after, you need the adjustable modulator as mentioned in previous post. they are cheap and available most anywhere.
Just turn the screw clockwise to delay shift points and reattach the hose. The more you delay (or tighten the screw) the firmer the shifts get.

If you are looking for later full throttle shifts, you'll need to fine tune the governor. There are kits made for this as well. The springs will tighten or spread the shift points too, both part and full throttle and have some affect on the rpm points. The weights will control the full throttle rpm points more directly,,,lighter weights will give you higher rpm shift points.

The cheap way to do it would be to remove the weights and grind some of the weight off, then reinstall. It's trial and error with alot of test driving.

Hope that helps. Larry.

[vtblazer]

Great info!

[Long Roof]

Let me start by saying I am not a transmission guy and I do not know if disconnecting the modulator is a good or bad idea, however I was always told that hard shifts were actually easier on the transmission. Of course this is hard on the drive train in general but as far as the transmission goes hard shifts reduces clutch slippage which reduces heat. Two of the worst things for a transmission are clutch slippage and heat, the former creates the latter. One example I have is my brother-in-law once had a Monte SS and blew out the 200r4 in it. He bought a junkyard transmission and had a competition type shift kit installed in it. This thing would squawk the tires in second at 1/4 throttle. Once the trans was at operating temp the trans temp needle never moved. This car was daily driven and bracket raced for 6 years that my brother owned it and many more after he sold it. The transmission held up just fine.