I'm seeking advice from the congregation. I have stock, very mild cammed 350/400 combo in a friends truck that I’m working on and I can’t seem to find a culprit to my issue. My issue is that when I shift from park to any drive gear it revs up slightly, slams into gear and stalls. I have to work the brake and skinny to keep it going and when I mange to get it in gear without stalling it feels like it has a lot of load on it as well. I couldn’t find any vacuum leaks, and everything seems to be getting vacuum from the proper location. The engines makes 18hg. The converter feels stock-ish and is to the owners knowledge. The trans fluid is fresh and so is the carb. The engine runs good otherwise. I'm leaning toward the converter but have never experienced this before and wanted to double check with you guys before I drop the trans. Thoughts?
What is the idle speed? and does it really change, when you move the shift lever? If so, that indicates it might not have any free play in the throttle linkage, which could be the problem.
Idle speed is about 750 in park and 850 in gear. The throttle linkage has enough slack for that not to be an issue.
Well, something funky is going on if it changes when you move the lever out of Park. Figure out what it is that's happening.
If you can't find anything in the throttle linkage that's causing the problem, then I don't know what it could be.... The idle speed is kind of high for a stock converter, which is why it clunks.
Why would the no load speed be higher than the loaded speed ? Try disconnecting the vacuum advance , reset the idle & test...
With a non-OEM carburetor especially, you'll want to make sure that the return spring is sufficient to close the throttle at idle. Also make sure the throttle cable/linkage isn't routed in such a way that it's putting itself in a bind. TH400 trans uses a switch for the kick-down, doesn't it?
I'd really double check the throttle linkage . Watch what happens when you drop it in gear . I've seen it be a problem , especially with cable throttle linkage !
How about a pic of the carburetor and what’s hooked to it? Could a bad/loose motor mount be clocking the engine over and pulling some on the throttle?