l have a 1980 GMC Jimmy full size 4x4 and recently needed a new tranny, a friend of a friend told me he could pick up a 350 and swap them right over...l soon found out was not so easy as the mount bolts didnt match, so he drilled in my frame so other then finding out they didnt just ''swap'' l now keep losing fluid from the front and yes l did have the seals replaced also when coming to a stop or taking off its as if there is a moment between the motor and my wheels moving..you can even feel it when coming to a stop! Does anyone know why this would be? What did this idiot that has also left town jack up? Also l notice the differant sizes for dipsticks...l have a 34in in it out of my last tranny but l see that the chevy turbo 350 takes a 27 in...sorry guys...shucks was of no help

DID YOU PRE-FILL THE CONVERTER ? DID YOU CHANGE THE FILTER AN FLUID ? DID YOU CK FOR BURRS ON THE CONVERTER SHAFT ? AND THE DIPSTICK IS LONGER ON THE 400. 350'S HAVE A SHORT TAIL AND A LONG TAIL SHAFT, NEVER TRUST A FRIEND'S FRIEND.

he probley put a newer type 350TH in the one that has a ele. lock up and you truck will not have controller for it.

l am surprised the transfer case fit the TH350 as they have a differint bolt patern and the driveshafts are differint .
He probably didnt have the converter in all the way and now you have a broken pump
He may have gotten a car Th350 and not a 4x4 as the cases are heavyer and no speedo hole machined from the factory

the 400 trans is longer than the 350 from the bell housing to where the tail shaft bolts to the main housing.and the torque converter is not seated into the front pump and most likely have broken the dog ears on the pump where the converter hooks up too..or your kickdown cable for the 350 is not there.??? because there is no kickdown cable on the 400 so they might not have connected this cable to the carb.this could be your leaking trans fluid?..