Automatic overdrives

[old51sedan]

I know there are several of you folks who have installed either a 200-4R or a 700-R4 into one of our older trucks. My question is How many of them have a stall converter in them. My trans guy suggests that is what I should do, any thoughts?

[jondancer]

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[Wrenchbender Ret]

My feelings are a high stall converter makes a truck or car miserable to drive. You have to rev up the engine before it takes hold & then it lurches. You don't need it unless you are going racing.
George

[Overdriven]

Stall speed is dependent on your engine combination and intended use. If your engine is mostly stock or with good low end torque and you want stock driving characteristics then a stock converter is fine. Same stockish engine but you want to fry the tires off the line easier then a higher stall speed will help. How? All converters will slip until engine rpm hits the stall speed at which point it will transmit the torque. Very basic explanation I know. Stock converters have a stall speed of about 1500-2000rpm, great for fuel economy but even a stock engine isn’t making most of its torque until 2500-3000rpm. Raise the stall speed to 3000rpm and it’s easy to see how the tires will be hit with more torque. The downside is until the converter hits the stall your throttle pedal isn’t doing much, some describe it as rubber banding off the converter. Imagine trying to pull a heavy wagon with a bungee cord and you get the idea.

But if you have an engine with a rowdy cam, single plane intake, big carb, a higher rpm screamer then a higher stall converter becomes more of a necessity. Engines like this sound cool at idle but they don’t make much power off idle and down low so the quicker you can get them to a higher rpm the better they’ll behave and the faster you’ll go. Put too tight of a converter behind an engine like this and it’ll cough, buck and probably stall out at times trying to pull through those lower rpms.

So what is your engine combo, rear gear ratio and intended use?

[Steeveedee]

I disagree with your trans guy. As is being said, it is unnecessary unless you have some kind of high performance parts. Note that the 200 and 700 have a lower first gear than what you have in the truck now (if it is an automatic). That will get you off the line just fine. And that OD is going to be really nice.

[jimijam00]

all these automatics have a torque converters, aka stall converters. the stall speed of those converters vary.

[Bigdav160]

The stall speed of the torque converter should be tuned to the characteristic of your engine. The diameter of the torque converter being the most important factor in determining the speed at which the converter stalls. Small converters have higher stall speeds and large diameters have low stall speed.

If you have so much cam overlap that the idle speed of the engine has to be, say over 1000 rpm, you need a stall converter, not only, so the engine gets into the power band quicker but a stall speed that is too low will cause the engine to pull against the brakes when stopped. No fun to drive.

A properly chosen, well made, stall converter will make the truck more pleasant to drive.

[old51sedan]

Most of you agree, that I don't need one and I don't really feel that I do either. I have never driven a vehicle with one in it that I know of. My truck is a 69 with a 3:73 rear end. I have a stock 292 engine, going from a 3 speed auto to the 200-4R. I'm not doing any racing, especially at 76 years of age. I have real doubts about a stall converter.

[weq92f]

.
With your setup and gear, a stock stall converter is going to do you just fine. Note that your 200R will come with a torque converter ( stall converter ). It must have one to function. The question then becomes at what RPM will it do its thing. Stock converters go around 1800-2000 RPM, which is probably perfect for your and most other stock configurations.

If you were replacing your 292 with an enormous Big Block that starts producing real power at 4000 RPM, that stock converter would make your truck a dog.

Hth,

-klb

[68Stepbed]

Keep in mind that all torque converters have a certain amount of stall speed. Even a "stock" torque converter has about a 1500 stall speed. 1800-2000 stall speed is usually referred to as a Corvette converter since they usually had slightly hotter engines, and designed to get that kick out of the hole.

For that 292, there's absolutely no need in going any higher than stock stall speed.

[HO455]

I may be misinformed but I believe if you go with a higher aftermarket stall convertor you will give up the convertor lock up function, meaning your highway RPMs will always be 200-300 RPM higher. A good compromise might be a factory Corvette convertor as they usually have a higher stall RPM and keeping the lock up advantage.

[old51sedan]

Thanks guys, my neighbor worked for GM hydramatic for years, builds transmissions for Baha racers all over the country. He knows these transmissions like the back of his hand, he says for me to just relax and he will get me what I need. I do have faith in him, so I told him to get me what ever he thinks I need. I'm sure it will work out, just don't seem right to me, but thats why I'm letting him handle it.

[Already Gone]

I just installed a 700R4 in my 72 with a stock 350 engine and 3:73 gears. haven't driven it a whole bunch but its great addition to a truck. There is a lag, for lack of a better term, between 1st and 2nd gear and found out its normal but didn't know that before install. I'm also finding its better just running around the City to drive it in 3rd and slip it into overdrive when on the freeways.