Hey I guess you can say I inherited a monster. I was given a free 1985 chevy silverado. its a 305 with a turbo 400. now this truck hasn't moved in two years, got her running like a top.... almost but I got to the tranny and here I tink there may be an issue I can't fully diagnose though I fear Im just overlooking something foolish. before this truck was parked the guy swapped in a brand new 305 block and but on a carb and distributor off a 72 camaro with a 350 and did headers and a full 2 and a half on it. now I know those of you who are familiar with the truck are already laughing going what the *** did this idiot do!. I know.... lol. well heres the problem, everythings free, no rear end lock up, no stuck brakes or bad bearings. when you put the truck in gear, it doesn't move. it sits still with the motor under load, you can without a doubt tell its in gear. when your in reverse you really need to get on it to move the truck, its the same in forward, you really have to work this *** and even then it barely moves, eventually it will piuck up speed but it fights you all the way, it as well feels like theres no power and it won't shift correctlly. keep these three things in mind, it sat 2 years, the fluids up, the intake was *** with so inevitably so is all the vacum. as I recall theres only a kickdown wire on here and thats not connected right now, what the *** could it be and could all this be a bad vacum situation i need to adress, if so what do I do. I need help  

Sounds like u got a !@#$%^ tranny!  Prly not a vaccum prop.  There is only one vaccum line on that trans and it's just for the modulator.  Shouldn't effect backing up and going forward.  If the truck runs well then there prly isn't a vaccum issue at all.  Is it a 2wheel or 4wheel drive?  have u pulled the pan off?  

LOL, I was hoping no one was going to say that, it is a 2wd and no I haven't dropped the pan yet, when the motor was swapped it had the system flushed.... sort of, there idea of flushing was running an extra quart or two down the hole with the pan off. i was planning to drop the pan and then the valve body and check out the status of its "inerds" from there. Im somwhat hoping its all gummed up or something. BUt yeah the truck runs great I have it tuned pretty well she runs solid and strong and as I said i KNOW nothings locked up in the front or rear. it just makes the truck work really hard to move it then once its going it just barely goes. what do you think, what do you suggest. I was told there were no issues at all before it was parked and that in fact it had had a rebuild about a year before the swap.

(this is me I had an issue with the account and accidentally deleted myself)  

i wouldn't be so quick to dismiss the modulator.  Same thing happened with my jeep- turbo 400- also this my be obvious or ridiculous, but make sure that the torque converter is engaged into the tranny.  

Sounds like the clutch paks in the auto tranny are fried. I had a 77 jeep cherokee with the th-400. The exact same thing started in mine as you describe it. Its a mechanical problem. I agree with waggychoppin. make sure the torque converter is correctly bolted up. And if its not.... just plan on replacing the flexplate. He probably fried the clutch plates while he was doing(the so called) flush of the tranny. You run an auto at dangerous low levels in a short time, say goodby and hello tranny shop. If it is the worst case, here is your excuse to build a bullit proof monster with lower planetary gears and valve body.
good luck  

*** I was hoping that wasn't the case because I couldn't personally see how it went from a great tranny to a hunk of crap just sitting. boggles my head but I think anyone whos been around can say they seen stranger. I'd like to be on the side of the budget here and first drop the pan and valve body, any suggestions from anyone on what to look for from there, what to possiblly do at that point. maybe someone knows something I could try like possiblly doing a proper flush and valve body rebuild. I stay the *** outta the inside of these when I can but thus comes my lack of knowledge!, open o suggestions from any and all, thanks to everyone so far by the way  

take it to a shop and have a proper flush done on it. Double check the flex plate to torque converter. You can also siphoun some fluid out and check the condition. If is dark reddish brown, deffinatly drop the pan, replace the filter, adjust the bands and replace with brand new fluid. That would be the first few steps I would do. good luck  

Hey Man Thanks for the advice. I've been holding out on the inevitable here till i got a bit more advice from a different source, I'll change the fluid out and the filter since I've got a bunch lying around here anyway. I was also going to install a pan magnet in there just because. I have a great tranny shop right around the corner from me, literally so I can try it myself first then if all else fails hobble it around the corner and get it done up. Like i asled before, anyone have any suggestions on changing up the valve body on this, its goinng to perdominently be a work truck with minimal weight in it cause of the flatbed and tool box, i'd like to change the valve body up to give it a bit harder if a shift and give it a little extra, its gunna get run believe me. thanks to everyone