I keep coming back to this post and wondering why, too. It would seem to me that a properly functioning stock converter would be perfect for this situation. I just don't see a need for any kind of "high stall" converter if creep is his only issue.
An engine that idles at 600 rpm needs a stock converter, one that idles at 700-800 needs some stall. I have a 3000 stall converter in my car <-- that likes to idle at 1000 rpm.
Squirrel, idle speed has nothing to do with stall speed. It's about getting the engine up into it's power band quickly.
I know that...but the two are related. A cam with a powerband that starts at 1500 rpm will idle smooth at 600 rpm. A cam with a powerband that starts at 2500 rpm will need to have the idle speed up around 700-800 rpm, to keep it running.
What's the tv cable have to do with it ? Check the line pressure at idle. Should be about 90 in p, n, 4 & 3 about 130 in reverse and around 200 in 1&2. To my understanding the tv cable acts much like a vacuum modulator, both control the boost valve in some way. when a vac mod is problematic or disconnected will cause a rise in pressure and plenty of creep. TV cable adjusted too tight or incorrect geometry can produce the same symptoms as a disconnected vacuum modulator. Maybe I need to adjust my understanding ?
That's where understanding the bell curves becomes relevant. Graph the curve from full slip of the converter to minimal slip over 1800 rpm and then do one for 2500 rpm. Compare the amount of slip at 600 and 800 Rpms
Maybe all the OP has to do is re-tune the motor to idle happy at 600 rpm in gear. There are any number of mechanical problems/misadjustments that will necessitate a high idle speed in order to keep it running smoothly when in gear. I'd sure be checking this possibility out before investing in a new converter...especially a new high stall converter that I'm convinced he doesn't need or want. Some people automatically put a "high stall" converter in their "hot rod" when it is first built and never experience driving it with a stock converter. To them the performance and driveability they experience is "normal", when in fact they might actually prefer the way the car drives with a stock converter...if they gave it a chance. I've driven mine - which is set up very similar to the OP's Chevy - both ways - with a high stall converter and with a stock converter - back to back on the same day. The difference in driveability was not minor, at least not to me. I would never use a high stall converter on the street (in a car that is not intended as dual purpose street/drag) unless there was no way around it. But, as I've pointed out before in this thread, opinions will vary.
maybe so. It looks like the engine has a pretty flat torque curve, starting at pretty low rpm. Assuming it's still stock.
Just to approach this issue from a completely different angle... How about low manifold vacuum at idle, low vacuum at booster, or a booster that's not up to snuff?
When idling in gear at a stoplight with any automatic transmission, the "slipping" that is needed to allow the engine to idle is 100% in the torque converter. These transmissions have some of their elements (clutches, sprags, bands, etc) applied for 1st gear and they are not slipping at all. In other words, the input shaft of the transmission is not turning unless the car is moving. Changing line pressure (or TV adjustment) will not affect creep, as the applied elements are still holding. If the Torque Converter (AKA "lockup") Clutch is dragging, well that is a problem that will cause creep as well as the engine to be loaded more than normal at idle speed. In other words the converter cannot slip properly as it is mechanically dragging. Trans cooler backpressure affects the TCC application/release, but I don't remember exactly how since my focus is on Chrysler transmissions. What will change the "creep" is the idle RPM and the converter slip. Increasing idle RPM will obviously make it want to creep more. Decreasing that RPM will reduce the tendency to creep in gear. Idle RPM can be decreased only so much, thus a looser (higher stall) converter may be needed if the engine cannot be made to idle at the stock speed. Of course, a deficiency in the brakes will make the creep problem much worse.
31Vic..., You are correct in that the TV cable controls the fluid pressure and shift points, depending on TV position and RPM. But at a stop, the only thing that comes into play causing creep is a torque converter that either doesn't have enough stall built into it, or is defective in some other way, like the lockup clutch dragging. The engine's idle characteristics determines how much stall the converter needs to have so you don't have to stand on the brakes to keep the car from creeping at a stop. TV position (or a bad vacuum modulator in a non-TV trans) is totally out of the equation.
I continue to think about the NEED for the high stall converter. Does a basic, stock Ramjet 350 crate motor have the need for a 2500 converter? Does this engine typically idle at 700 to 800 RPM's? I would look at idle issues first, before swapping out for a bigger or better converter.
One more vote for a higher stall converter for street use. I prefer being able to put a car in gear without the clunk. It only takes a little throttle to make it creep, and a lot more makes it haul ass. There is a fine line for the "proper" converter for any given combination and I do not know how you get there without trial and error. The OP obviously does not have the right converter OR, as has been stressed before, it's lockup is on at idle or low speed. If OP is happy with brakes he needs more slip at idle, if he is happy with converter, he (she) needs more brake pressure. Lots of good input here.
Best thing is to talk directly to a converter company, and get them to build one for your specific setup.
I'd just see if the mill will idle a bit lower- it seems pretty tame. What does it idle at in nuetral vs. in gear? The fact that it pulls hard enough for someone to complain could just mean the converter is not what it was advertised as. -rick.
First off, there is no such thing as a "2500 converter"...the stall speed of any converter depends on power input and a converter that actually does stall at 2500 can be built either "loose" or "tight". I have a Chevy crate motor with a 700R4 and a converter that's supposed to be 1800 and it idles fine in gear. The OP states that it takes "moderate" pressure on the pedal and that's exactly what I'd expect....of course, "moderate" is in the foot of the beholder. I'd go for stronger brakes for the old lady.
Has the tach been verified to be accurate? If the tach says 800 but it is actually at 1000 this scenario could be entirely possible...
The Jalopy Journal
