I've got a 79 with *gag* automatic transmission.

Once the engine and tranny get warm it doesn't like do the kick down...like it should...seems to be okay while it's relatively cool.

 Thanks...

    Jim

JimG38415.2841898148

have you tried the easy stuff..

vac modulator, trans filter ?  these are basic maintenance items that get overlooked and make a world of difference

[QUOTE=cthulhu]

have you tried the easy stuff..

vac modulator, trans filter ?  these are basic maintenance items that get overlooked and make a world of difference

[/QUOTE]

Ya know I thought about the filter after I wrote that...  I hadn't even considered it....  I'll probably change it Sunday if I can get the parts by then.

I'm not sure that I know how the vacuum modulator works and where to look.  All I've picked up is that it is connected someplace to the Master cylinder.  Not sure what I'm looking for.

 Thx everyone.

 Jim

Jim, the modulator is what tells the trans how hard your on the gas. It basicly controls the upshift feel(harsh/soft) depending on how much load the eng. is under. It is located at the pass. side rear of the trans on a 350, and on the pass. side front on a 400. It is a small, round, canister-looking thing. Pull the vaccuum line off, and see if any trans fluid runs out of the line, or the mod. If it does, the mod. is shot. If the mod. is bad, though, it usually creates a late, hard shift, at all times, and you would be having to add fluid, because it would be getting sucked up into the motor, and burned. You would be seeing some white smoke comming out of the exhaust. The kickdown cable is what controls your kickdown, or 'passing gear'. It either works or it don't. It don't care if it's hot or cold. It is a mechanical linkage(cable) from the carb. to the pass. side of the trans, by the filler tube. It sounds like you MAY have a vaccuum problem once the motor warms up. Check the metal line comming off the back of the intake mnfld. going down to the trans. There will be a short(2 inch or so) piece of rubber hose there. Check to see that it is in good shape, and doesn't fall apart when you move it. There is anouther short hose at the mod. too; check it, also. If you find the hoses in good shape, you should check for good vaccuum signal at the trans, both cold and hot. You could have a restriction in the line the makes it hard for the vaccuum to respond to engine load. If all this checks OK, then pull the pan off the trans, and see how much crap is in it. If it's not too bad, no more the maybe a 50cent piece size of doo-doo, then go ahead and change the filter & fluid. If there's more than that, it's time to see the trans DR. This info is for a 350 trans. If your's is a 400, the kickdown is 'lectric, but it uses the same vaccuum setup. This all assumes that you are not having a motor issue, such as late ign. timing, or a bad vaccumm leak somewhere else in the car.(A Vette with a vaccuum problem? )Adams' Apple38415.8302777778

Nice description Joel.  Nothing I can add.

[QUOTE=Adams' Apple] It sounds like you MAY have a vaccuum problem once the motor warms up. Check the metal line comming off the back of the intake mnfld. going down to the trans. There will be a short(2 inch or so) piece of rubber hose there. [/QUOTE]

Hey Joel or Ken,

 Is that the one near/on the Carb (hooks into the carb?) ?  Getting ready to leave work. I'll have to see if I see any others off the intake, if not. I was under the hood for a while day before yesterday on the water pump and don't remember seeing much else, but then I was working on a different part of the engine and not looking for vacuum hoses.

 Thx Guys !

  Jim

JimG38416.5055671296

Never mind... I found it... It comes up right behinds the Carb. Goes up about 2 inches and T's, then one end goes to the Tranny.  Looks a might loose so I'll replace. 

 Thanks Again !
 

   Jim

Okay,

 New Problem - Now I'll be cruising at about 65 or so after the tranny gets good and warm, and all of a sudden it's like it goes out of gear. It's got tranny fluid so that's not the problem.  I did change 1 vacuum hose near the intake. I can get it to go back into a gear by putting it in netral or Low 2 and back to drive. and it's fine for a bit. Then it does it again.

 What do you think, Modulator or Filter ?

 Jim

since it chaged behavior when you fixed yor vacuum leak..im gonna say modulator..

personally..  the modulator and filter are very cheap.. and easy to install..  id do both..