what do they do on oh...say a th400? i'm working on a truck right now its a 87' 2500 sb350 and th400. we have some problms with it and one is that when put into gear it dies. well we noticed that when you put it in gear it shifts really hard like as in it looks like the motor is about to jerk itself out of the eng bay. and i remember before when i went for a ride with this guy he would floor it and i swear it never down shifted. he says it did but i never felt it. we took the modulator off and hooked a vacuum pump up to it and it move in with vacuum and out with out vacuum. the other guy working with me tried to push the peice in the trans but it didn't do anything i guess.



so with that being said, in park the eng idles great and sounds good. but when you select a gear it looks like the motor is about to jump out and the hole truck jerks in the direction of the gear selected. after the gear is selected the eng idle down and you can tell its bogged badly and after a second or so it will die. i uped the idle speed and it still dies. so i think the trans is bogging the motor badly and i think it has something to do with the module. am i right and hat do i do or need to check?

oh and when i disconnected the vacuum line it changed nothing expect for a higher idle do to vacuum leak but we pluged it. and i put a vacuum pump on the line going to the tranny and pulled over 20"s of vacuum on it and that changed nothing. so how can i check if its the trans or not?

 

I can tell you that some of the factory TH400 converters were EXREMELY tight. I've seen one that would bark the tires when you put it in reverse. Is it the TBI motor in the 87 or has it been converted to carb? Also timing off and carb adjustments can cause the stalling.

 

Vacuum modulator will do nothing but control shift firmness. I don't think it has anything to do with your problem.

 

Yeah the vacume modulator controls what rpm it shifts at part throttle primarily. The govorner controls shift rpm at WOT from my knowleged. The stalling is most likely an engine issue.

 

well, its tbi with electronic timming. you are suppose to set timing at zero with the little plug disconncted when your done you turn off the eng and reconnect the spark advance wire. after that you start it back up and the ecu controls timming from there. he has a edelbrock chip in there for the edelbrock heads intake and cam package. some reason the retard took out the roller hydro lifters and put in flat tappet hydro lifters. the cam we replaced was bigger than what we put in there. but hey what ever the costome wants right.?. so what else could it be? i tried to crank up the idle but it just made the shift into gear ruffer and then it still boggs back down and stumbles and dies. if you put it back in gear before it dies theres an odd grind noise for a second and then it goes to park and the idle comes back up and smoothes out.

the truck i guess is an odd ball mix between 87 and 89 first part of electronic fuel and timming but not computer controled trans. something like that.

 

oh and this is the first of the v-series. vise the k-series

 

when I had my tranny built I asked Art about doing the vacuum modulator mod, he said not to do it and just let the electronics handle it, that's one shops opinion on it anyway.

 

this one is a 87 model. its stock

 

LOL

I read TH400, but for some reason 4L80E stuck in my head

 

So basically, when you put it in gear, it jerks hard and then dies? Problem with the converter maybe?