J0386

Hi I got a 1991 1500 with a 350/350 and for some reason the transmission only has 2 gears it dosent shift into a third gear but it dosent slip or anything like that it just dosent shift after 2nd but drives fine it has a small shift kit for hard shifts but don't think that's the problem because i had another t350 in before this one ( and before i let my friend borrow the truck and he burnt up the trans ) and it did the same thing could it be a rearend gear problem or maybe a carb problem seeing how my holley 4bbl has a vacuum line that hooks to the transmission vacuum modulator i have no idea im not a transmission guy so any help would be great

OLD WRENCH

The modulator helps with the shifting and they do go bad. Pull the hose off of it and look for trans fluid in the hose. If there is any the mod is bad.

J0386

theres no fluid in the hose, dose the hose have to be a cretin length? i know some vacuum hoses have to be the right length or could it be the carb. its an old carb. a few months ago i had to replace some gaskets on it because it was leaking gas.. but ill replace the hose tomorrow and see if that dose any good but everything on the trans should be new it was rebuilt at about 5 months ago

OLD WRENCH

The length of the hose is not important. You dont have it hooked to the carb do you? It has to me hooked to manifold vac.

J0386

ya its hooked up to the side of the carb.. where at on the manifold dose it hook up to i see only one vacuum port and the brake booster is hooked up to that.. here is a picture of where on the carb its hooked up

old dog

that hook up point is a no-no ,there need's to be a port at the back of the intake manifold that allow's you to hook up to manifold vaccume .what intake manifold is it ?there is usually a pipe plug ,the fitting has two to three ports to plug hoses on to .kinda looks like a eldebrock performer here is a picture the port is on the intake runner behind the carb mount flange .
http://www.edelbrock.com/automotive_...ormer-sb.shtml

J0386

its an edelbrock performer and i found the vaccuum hookup but it only has one olace to put a hose and the breakbooster is hooked to it, so ill have to go buy one that has the multiports on it, what hooks up to that place on the carb? damn if that is the cause of loosing 2 transmissions i know a buddy of mine who is going to get one hell of an *** whoopin'

old dog

that port on the carb is for ported vacume like for a vacume advance .but you have to find out what your accessory's require before you jump to conclusions .
i dont think the vacume source for the modulator valve could cause the trans to fail .but find out for shure what vaccume is required for it to work .turbo 350's are pretty good transmissions but they can be a little weak in the foward clutch -pack area. i have tosted two of them with higher stall converters and shift kit's before i went to a turbo 400 .

usmarine0905

I agree with Old dog, that is a no no connection. I dont think there is enough vacuum there for the trans in the first place. you need to find another port of vacuum

J0386

would it be enough vacuum if i ran a splitter off the hose to the breakbooster to the trans or should i get a splitter to run off the manifold?