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Converter stall speeds

Most stock converters have a stall speed of 1,800 to 2,000 rpm. The higher stall speed your converter has should not be a problem on a daily driven vehicle. You didn't say what kind of transmission you have but if it is an overdrive unit like a 700R4 and you are running a relatively high (low numerical) rear end ratio you could run into some problems. For example, I am running a 2,600 rpm stall converter in my street rod with a 700R4 tranny. With my final drive ratio and tire size, at 70 mph my engine is only turning 2,100 rpm so I am still in the stall range of the converter. However, I also have a lock-up converter in the car so it is locked up and not slipping like it would be without the lockup. In fact, if I didn't have a lockup converter I would probably have to go 90 mph before I was out of the stall speed of the converter.

Constantly being in the stall speed of the converter will overheat your transmission which will substantially lower the life of the transmission. So a cooler is a must. The B&M coolers are very efficient and nearly indestructible. It is critical that the cooler be where air can freely flow through it and not buried somewhere in the chassis. Additionally, it can be a good idea to get a cooler with a thermostatically controlled fan on it. The reason for this is when you are driving at low speeds, like through town, your car is not moving fast enough to get an adequate flow of air through the cooler. And this is when you need it most because town driving with a high stall converter is when it will tend to heat up quicker. I also highly recommend a trans temp gauge. B&M has those also. Your trans temp should run in the 160 to 180 degree range for maximum trans life. Most hot rods and street machines do not have trans temp gauges and I would bet that 90% of them are running too hot and then the guy wonders why he only got 20,000 miles out of his tranny.
 

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I figured with the detailed B&M description, that it must be the same person. I learned along time ago its not what you know in our industry, it is who you know.

Chris Straub
Stef's Performance
B&B Performance
 

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Tire size also enters into the equation. But 3.37's are a pretty high ratio. A 350 is not an overdrive tranny but with 3.37's and assuming you have a decent size tire, you could be in trouble with a 2,800 rpm stall converter. My "dream wheel" as we used to call them, is at home. It is a circular calculator that you can set your engine final drive ratio, tire size, and rpm and it would tell you how fast you will be going. Isky used to sell them. Maybe they still do. If you are good at math you can figure it out by yourself. As a very, very rough guess....and I could be off...I am thinking that you will have to be going at least 60 before your converter gets out of the stall speed range. And not knowing your tire size....for sure that is just a guess.

On my '33 Ford, I am running a 3.90 rear but with a 70% TH-700 overdrive, which would be the same as a 2.73 rear. But I also have really big tires....32" which is the same as running a higher ratio (lower numerically) rear. As I said before, with that combination I am turning 2,100 rpm at 70 mph. With smaller tires, and a lower gear ratio your engine will be turning a lot faster....good for a high stall converter....bad for fuel economy.

If you do go with a higher stall converter, just make sure you have a big trans cooler (preferably with a fan as suggested earlier) along with a trans temp gauge so you know if you are getting too hot and can pull over and let it cool down.

Special note to Chris: Who you know is good. But what you know also helps a lot too.

I just remembered that GM made a lock-up convernter for 350's. Whether B&M, or anyone else for that matter, makes a high stall version of this converter, I don't know. You might call B&M and ask them. A lockup converter is frankly the way to go if you can.

When I first built my current street rod, I burnt the tranny up in the first year because 99% of my driving was in the stall speed range of the converter. So when I had the trans rebuilt, I had B&M make me a stall speed lockup converter. B&M also has a device that you can use to control the point where the converter locks up. I have mine set to lock up at 40 mph. That was nine years ago and I haven't had a problem since.
 

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Discussion Starter · #15 ·
well i will probably be doing a lot of stop and go driving also some streets around where i live have 25 or 35 mph speed limits and i must follw them (i have already gotten a few speeding tickets) so do u think a stall converter is even the way to go? i mean i just want my s-10 to be able to shut the mouths of some of the camaros & 5.0's around here that think they're the ****
 

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Like Jim said, keep it cool. I've got an ac condenser on mine for a trans cooler. It's overkill but I have a Trans Specialties Big Shot 10HS converter that flashes to 3600rpm off idle with 3.73 gears. Even with the big cooler up front with an electric fan, the temps hover around 190 when I go for a ride in town.

Keep it cool.

Larry
 

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hi stall converter on the street

The selection of a converter has a lot to do with what you have for an engine. If you have a fairly light vehicle....which I assume the S-10 qualifies...and an engine that makes good bottom end torque, then you really don't need a high stall converter.

But if you have a small displacement engine with a really big cam and a single plane manifold or tunnel ram, then you have an engine that doesn't make a lot of low end oomph and you need the high stalll converter to allow the vehicle to launch with the rpm's up where the engine is starting to make some power.

On my own car, my engine makes gobs of low end torque so from a launching standpoint a high stall converter is not needed. However with a light street rod (I have a '33 Ford 3W coupe) and a higher than normal idle, the problem with a tight converter is when you drop it in gear, the car lurches forward. That's the only reason I put a higher stall converter in. Turned out that my initial converter was way too high. Rated by B&M at 2,400 it actually made closer to 2,800 or 3,000. This is because B&M's converters are rated at a specific torque output and the more torque your engine makes, the higher the stall will be. My engine was making a lot more torque than B&M's rated torque.

So when I changed to a 700 lockup, I had B&M make it from a totally stock 700 converter, which on a stock engine makes about 1,800 to 2,000 rpm stall. But in my car it is closer to 2,400 to 2,600. My car idles at 600 rpm so I could easily go with an even lower stall converter but I am running a stock one already. I suppose I could have it modified by bending the fins backwards to lower the stall but I am not up for pulling the trans out for that since it is working ok as it is.

Anyway, to recap, you may not need a stall converter if you have a light car and decent bottom end power and torque.
 

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I would think you would definitely be ok as long as you have one of the fan units.

As mentioned before, I do like the B&M design cooler the best of all the ones on the market. I don't know if they offer one with a fan as I don't have their current catalog in front of me. But I seem to recall seeing that they had added those to their line.

When you say 2,200 to 2,800 stall, that's a pretty wide range of rpm. Are those the numbers given by the manufacturer?

2,200 is pretty streetable while 2,800 is pushing it.
 
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