Auto trans issue ?

Has anyone converted their tranny to a th350 behind the inline 6 ?
Since I converted to the auto trans. It shakes when in gear..took it to a tranny shop and they said it was the flex plate, replaced the flex plate this morning and still quite of bit of shake. The rpm drops 450 ....it runs down the road smoothly, it only shakes when in gear with foot on brake...
Has anyone experienced this?

Swapped out the old distributor for an HEI unit to see if it would improve, runs better but the idle issue is still there...When in drive or reverse it is idling at 550 rpm. I will try the carb cleaner tomorrow....i have checked for vacuum leaks, none found...still perplexed !!!!

spray the carb cleaner on all gasket surfaces - carb & intake area - sommthe out? run better temporarily?

i did an auto behind a six, had the same problem
I think the stall rpm of the converter is the
source of the problem, it is too low, needs to be
a higher rpm, like a 2000/2200 stall converter.
I have not switched it yet.

i have a 2000 rpm stahl from my th350. i didnt have the shudder, but it was alwats dragging at idle/redlights and shifted too early. 2k converter woke it up and acted like a bigger motor. i had it installed for a month then went to a 700r4. i usually give my stuff away but this is like new, 400-500 miles. trade for ??? or half of a new one. think it was just over a hundred but i will check. free if you come get it.

I replaced the flex plate...still the grabbing shakes...today I checked for vacuum leaks.....no vacuum leaks...zeroed in the timing....air fuel mixture....and still the grabbing while in drive and foot on brake...i am convinced it is the torque converter....too low of a stall ( 1300 rpm ) after talking with a few tranny shops and the advice on here...i think the clutches in the converter are grabbing while at idle...Will take it back to the Transmission shop I got the converter from and see if they will replace it...

go back and check vacume at idle. i had all the same 'grabbing' issues. the 2k converter made a huge difference in cruising but only a little help at idle. also check kickdown cable, mine was sticking inside, so i was always running to much preasure. i found it when i had converter and tranny out but think it was too late. it ran really good the last 400 miles of its life.

Jrinaman, hadn't thought of the kickdown cable being an issue ....I will try that tonight...thanks

So I have found a vacuum leak at 5,6 intake ...replaced intake gasket , no vacuum leak on the intake....now another problem has surfaced....when the van is cool it will fire right up, let it get up to operating temps shut it off, it won't turn over, it's like it is pulling way to much amperage off the battery and the battery does not have enough umph to turn it over.....let it cool all the way down , hour or so it fires right up..timing? Starter? Relay? Solenoid? #%! Starting to frustate the day lights out of me...had the timing set at 6 advanced, tried 8, still does it...still the issue with shaking when put in gear....any clues or advice ?

Starter-replace = yet!! I do believe there are other problems ur having too. Does engine idle smoothly in park/neutral?? if not check / replace spark plugs & wires!1=then retest. all ok? if idle is stable in p[ark-id look @ kickdown canle - and most all TH350's ive seen have NO Converter clutch!- if still chatters - there may be a problem internal to tranny- low or a pressure restriction in the clutch pack?/ also maybe as some ststed kickdown cable sticky or bad ?? im going with pressure problem & that can be tested by a good tranny shop or you-if you have the equip?? let us know about the plugs & wires? Ive actually had some bad spark plugs right out of the box - rare yet happened.

Twin p I replaced all the wires and plugs and installed an hei last week..all is good there...set gap on plugs to .045 for the hei...I pulled starter off and took it to auto store to test...kinda weird, it will initially pull right at 150 amps then taper down to 120, to much draw from the starter and it is killing the battery...so ordered a new starter from summit. High torque type seeing as I will need this for the new motor anyways and also going to install new battery fully charged before intinial start up...
Charging the battery that I have it has been on the charger for 3 hours and is still pegged at 8 amps the needle has not moved a bit
Donivan,
What is the setup procedure on the ford relay and does it eliminate the chevy one?
The ford

donivan thank you for the help.
on the chevy starter (#1) the main lug holds the positive from the starter and the main power to the ignition...(#3) holds the green from the ignition switch.. are you saying to make a jumper from #1 to #2 (ford relay) take the green wire from the chevy starter and put on #4 (ford relay) and then make a jumper from #5 ( ford relay) to #3 on chevy starter...? as far as grounding the ford relay any metal structure is ok?
Thank you again !

Maybe I'm missing something in the set up for a 6 but why not just jump on the starter instead of running back up to the new solenoid?

Can't the neutral switch be wired at the new Ford sol. ?

Digz the picture you show is like jumping the solenoid with a screw driver blade...do you have a relay in place? The power wire from the starter goes to ignition when the ignition is turned on the now powered green wire from the ignition sends power to the solenoid completing the circuit powering the starter...like donovan said that is a long way for the power to go and return to just start the motor

Yeah Im running a Ford relay also. My object was just having fewer wires running next to headers. Not such a big deal on a 6. This is my birds nest panel for the engine/fan stuff.

lower post goes to battery and feeds everything. upper is the only cable that goes to the starter. the other small one is from the key to engage it.

No Don , I dont have a fusible in there. I was looking at it and a good spot for one would be right there from the Bat post to the horn relay. beyond the second power relay everything is fused or on a circuit breaker. I have all my engine Acc power running thru a 25A constant On relay triggered by what was the Coil RUN wire, upgraded of course, alot of guys think this is bad , but one advantage I have here is anything is easily by-passed in a pinch.