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When brakes applied it will stall. bad vacuum or torque converter? Rookie owner

69 Coronet R/T

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Jul 14, 2014
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So i need some help. I just bought the car and it has a 383 (440 was the original in 69') and the 727 TF trans. it is on jack stands now and idles approx ~850 RPM, dwell is 32-34, timing is ~15 TDC. It will shift into gear but then when brake is applied and it begins to slow the wheel rotation the engine RPM slows as well and stalls. Tried removing the brake booster vacuum line and plugging but same results. Most people seem to immediately guess vacuum leak, is this correct or could the trans not be slipping at lower RPMs? Any help is appreciated, thank you in advance! i feel like it is close but i am missing something easy or maybe not.
 
doesn't sound like a booster problem, more like a transmission problem
 
Converter won't disengage.... could be bad converter, stuck throttle position valve causing high pressure or something stuck in the valve body... pull the trans pan and look see or take it to a trans shop.
 
Try raising the idle speed to around 1000 RPM. Also initial timing at 15 degrees advance WITHOUT vacumn advance should be about right.
 
where would i look for a stuck throttle position valve? when i pull the pan what should i look for as well? Thank you for the reply, i want to get it back on the road so bad and this is the one roadblock i have.
 
Be patient and sort it out... the throttle position lever is the kick down lever above the shift lever. it should move quite freely until the last 3/8" of travel when you pull the pan it should be nice and clean in there... and if you play with the lever you will see what it moves on the valve body... if you don't know transmissions other than inspecting for a lot of gunk and some springs or parts in there don't touch it beyond a filter and pan gasket..... if it looks good in there a little sediment is ok put the pan back on and bring to a shop for a specialist because you will have to drop the trans out to get at the converter. But check the idle like mentioned above also and any binding linkage.... either way it's a shop if it isn't some thing from the out side... to adjust anything you need a book and some experience... a hurry to get it on the road will be a disaster if the trans is not spot on... there is no quick fix in side it.
 
Happened to me too and my vacuum advance lever was stuck from me disassembling and not correctly putting it back together. I didn't know this could cause the brake stall issue.
 
when my car was doing this, it was because i had too big of a cam, with low compression, and a crappy carburetor....the trefecta of bad luck, and poor planing.
 
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