Hi all. Got a tranny question cause I dont know much about how they work inside. Had a guy rebuild mine and shifts great but there is a delay when I shift. Around 2-4 seconds and I usually have to let off the gas some or alot at times. Annoying.

Its mounted to a basically stock 350 with mild cam. Seems to have good vacuum cause power breaks work good (tranny has vacuum line connected to it). stock stall converter (new when rebuilt).

In the process on swapping engine. New engine has way bigger cam with probably less vacuum. .480 lift on int. and exh. New converter with 3,000 stall. Is this setup going to amplify my shifting delay or make it better with less vacuum? If not what can I do to make it shift instantly when I move shifter? No delay and no lifting on gas pedal. Just move shifter and BAM, in that gear.

 

Sounds like it has the big black can vacuum modulator on it.

GET RID OF THAT.

Then go to the parts store and get the small gold-colored VM with a red stripe. Not green, not magenta; RED. You can't look it up just that way, but it's easy enough to look up all the GM ones that exist (a grand total of exactly 4 different part #s: big black can, small gold can w green stripe, small gold w magenta stripe, small gold w red stripe), open the boxes, and pick the one with the RED stripe.

Pop quiz: what color stripe are you looking for?

Might want to consider a shift kit as well. Get a Transgo one, NOT B&M. Set it up for one of the milder modes, you'll find that the "full race" setup is all but undriveable on the street. You could try taking the spring out of the 2nd gear accumulator, but that tends to be a bit ... harsh; try it out and see if you like it, but don't throw it away.

 

Also make sure your vacuum line isn't collapsing under vacuum. Happened on my old 85 and it kept killing transmissions. I sold it, then figured out the issue.

 

When you say vacuum modulator do you mean the one on back of trans. or the one that is on the opposite of the battery tray (drivers side front). Is the big black canister under the hood for vacuum storage?

 

http://www.bulkpart.com/2/product/35...or/44160R.html

The thing under the hood is a vacuum reservoir, not a vacuum modulator. Not related to the transmission in any way.

 

Made most of my trans. vacuum line from a long piece of steel brake line. Still has short lengths of rubber hose connecting it to carb and another to trans. If they are collapsing, and trans is loosing vacuum. That'll cause a delayed shift?

 

ok thanks. understood

 

If the one by the trans isn't the molded 90° "special" piece that comes with a modulator, and if it has a sharp bend in it, then yes it could be collapsed, and yes, that can make the transmission shift funny.

Use the one that comes with your new red stripe modulator, if whatever you made out of the steel line, requires a 90° at the transmission.

 

Are you talking about a shifting delay with trans left in drive and trans shifting it's self in auto mods..... Or you manual moving the shifter and shifting gears?

Stock type auto trans WILL NOT shift the instant you move the shifter. They will all have a delay.

To get that instant manual shift you need an upgraded/aftermarket/modded valve body and shift kit installed in the trans. Like a transgo reprogramming kit, Or use a manual/auto or full manual valve body

 

When shifting manually at WOT I have a delay. When cruising around it shifts to early. I try not to lug engine and trans so I usually shift manually all the time.

Forgot to mention that when I come to a stop in drive or second gear it seems to stay in second gear when I take off. I have to manually put it in first.

 

How's that red stripe modulator working out for ya?

 

I dont drive it this time of year. salty roads=rust. Also in the middle of swapping engines at the moment. thanks again for the info. I know where to start looking when its road worthy.

 

Has had a red strip vacuum modulator on it this whole time. Been focusing on motor swap but thought I would run that by you.