Automatic + stall converters. driving feelings? [Archive] - Team Camaro Tech

: Automatic + stall converters. driving feelings?


Marc
Oct 12th, 01, 04:02 AM
Hi.
I have never driven a V8, neither an automatic tranny. Though I know how torque converters work. What is different when driving a car with a 3000 RPM stall converter, and another with 2100 or 2500 RPM ?
I know the stall converter will slip to those RPM speeds, but what are the driving feelings differences?
I also guess a higher RPM torque converter will heat more in city traffic.
I think I 'd prefer a low RPM torque converter (max 2500) with a very torquy engine. But would that mean I wouldn't be satisfied if driving a car with a 3000 RPM stall converter? I know the engine makes a lot for the torque feeling too, stroker or not, the cam duration numbers,... I am only asking about the stall converter.
I also guess they are linked : high RPM stall converter with a high RPM power engine.
Thanks to let me know.

Also : how much does a 700R4 tranny + 2100 stall converter cost? All together. Do we need to change both ?
Is that difficult to swap a stall converter?

Marc

Tracy Focht
Oct 12th, 01, 06:08 AM
On some engines, you may not even notice the difference between a 2500 and a 3000 stall. I drive mine everyday with this 3000 stall. After you drive a car with no stall, then add a 3000 stall, it seems like you are stretching a rubber band. Really revving to get it up and going. But you get used to it really quick.
Stall will just play a part, depending on what is your motor and rearend combo. if the cam is too small, sometimes a stall isn't even needed. I've heard anything under 230@.050 doesn't really need a stall. And need deeper gears for larger stalls to keep from slipping all the time in town.

Hope this helps! http://www.camaros.net/forum/biggrin.gif

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383 Speed-O-Motive stroker kit with Holley 750DP, RPM intake,MSD6a box,World Products Sportsman II heads, ported and polished with 2.02/1.60 valves,64cc,TRW forged pistons with 10.7:1 compression, Comp Xtreme 284 cam,Crane pushrods, Comp Cam 1.6 full roller rockers,ATI damper, 40 series Flowmasters, 4.11 gears with TH350 and Hughes 3000 stall.

camaroman7d
Oct 12th, 01, 06:30 AM
You need to pick your stall speed according to your engine (cam), rear gears, vehicle weight and intended use. The convertor will not slip to te stall speed every time you leave a stop light. Stall speed will vary according to how much torque you put to it. The more torque the higher it will stall. If the engine you have has a powerband in the lower RPMs then you need a tighter (less stall) convertor. If you have a big cam, single plane intakeand or light car, then you will want more convertor. If you want some good suggetions you could post the rest of your combo and the guys here will be able to get you in the ball park. You could also call a convertor company and they can help you. They will want to know Engine size, cam specs, vehicle weight, horse power, rear gears, tire size and intended use. 3000 is about as high as you will want to run on the street, but tbhis also depends on a lot of things.

Royce

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70 Camaro 383ci
69 Camaro 385ci
2000 GMC Z71
Link to my 70

http://profiles.yahoo.com/camaroman7d

Marc
Oct 12th, 01, 07:55 AM
Thank you.
And what about the cost of the parts?
a stall converter, and a 700R4

Marc

boodlefoof
Oct 12th, 01, 10:35 AM
Marc,

You can get a non-lockup converter for the TH350 with a 2000-2500rpm stall speed for under $300. The higher the stall speed, the more they cost.

I have seen packages for overdrive automatic transmissions (the 700 or 200) with a lockup converter and trans cooler for around $1700. The ones in this price range can handle around 400 horsepower according to the builders. The more heavy duty they are built though, the more they cost.

Marc
Oct 12th, 01, 11:32 AM
thanks.

sr71bb
Oct 12th, 01, 02:36 PM
My friend has a 496 with @ a 3600 Stall convertor and it is not desirable at all for highway driving. Of course it gulps gas as you can imagime. My car however has around a 2600 Stall with a 700R and roughly 600HP. The tranny has been a real challenge in terms of making it work with this much torque and HP but it has lasted so far even with periodic nitrous use. This tranny would be roughly $2500 to duplicate because as already mentioned, heavy duty parts are EXPENSIVE. Down here in Dallas, $1400 will buy you a nice 700R but it wouldn't last that long behind my motor.

My opinion is that 2600 stall is about perfect for street use. If the car doesn't launch hard at that RPM then you probably need to work on other things.

.

[This message has been edited by sr71bb (edited 10-13-2001).]

[This message has been edited by sr71bb (edited 10-13-2001).]

1968camaro123
Oct 12th, 01, 03:16 PM
So if I put on a 3000 RPM converter it will make my car accelerate slower until I get to that RPM? Just curious cause I don't know much(anthing) about tranny's or converters.
Thanks alot,
Donnie
P.S. The reason I'm asking is because the comment was made that it would seem like you're stretching a rubber band or really revving the motor if you've never had a converter and I haven't.

sr71bb
Oct 12th, 01, 04:02 PM
Ok the way it works is this. Say you have a 3000 stall convertor and you are going say 55MPH with your 3.73 gears. At this speed you would be turning around 2500 (depending on tire diameter). IF You now FLOOR the car, it would IMMEDIATELY feel like the car's tranny was slipping momentarily because the convertor has not gone beyond it's stall speed. A good rule of thumb is that the MAXIMUM stall you should run (assuming you are also running on the street) is 200-300 RPM LESS than whatever RPM you cruise at on the highway. For example I cruise @ 2800-2900 RPM so my suggested max. stall spped for my convertor should be roughly 2600 (which it is).

In the 496 example I cited earlier, if you pull away (say light throttle) away from a standing start and watch the tach, you can see that it momentarily goes to 3600 rpm not because the tires are slipping but because of the high stall convertor. On the highway the car feels as if you momentarily have it in neutral just prior to it "catching" in a sense.

Slippage does cause heat. Auxilary tranny coolers are more or less REQUIRED on cars with 2000 or more stall sooed convertors. Slippage also causes poor gas mileage. the 496 with the 3600 stall convertor gets maybe 6-7 MPG. My car with approximately 25 more HP gets 11-12 MPG. (yeah, I know guys it's apples and oranges but the point is high stall convertors KILL gas mileage for those of us interested).

I guess I would describe the effect of the convertor prior to reaching stall speed is the same feeling as if you were runnning a standard tranny with the clutch slipping. It is still engaged all right but you are not getting the full throughput of the motor.

[This message has been edited by sr71bb (edited 10-13-2001).]

1968camaro123
Oct 13th, 01, 08:56 AM
Okay, so if I switched from my stock converter to say a 2500 or 2600 RPM stall in my TH350 would there be a noticible difference or not? Basically is it worth the money and how much of a difference does it make?
Thanks,
Donnie

transfixleo
Oct 13th, 01, 11:47 PM
The proper stall speed depends completely on the power band of your engine. This means that if you have an engine that starts to "pull" at say, 2100 RPM and you have a 1600 stall converter, your performance off of the line will not be at it's best. On the other hand if you put in a 2400 or 3000 stall you will be wasting expensive power, since the converter won't be passing the maximum power to the tranny until later in the power band. In the example I used, a 2000 stall would be ideal since you will "flash" up a little bit on take off. You will then be at the optimum take off RPM. Sometimes too, people have the proper stall converter for the engine combo but have the wrong rear end gears to fully utilize the power.

Eric68
Oct 14th, 01, 04:12 PM
Keep in mind that a torque converter does more than just "slip" until it reaches its stall speed. A torque converter multiplies torque and can store energy when you hold the brake and apply the gas at the same time. It unleashes that power when you let off the brake to launch the car. For that reason, usually a higher stall speed allows for faster acceleration right out of the hole.

I drive a 68 Camaro with a 3000 RPM stall and 3.55 gears. I cruise at 60 mph at 3100 RPM. When I launch the car at the track I hold the brake real hard and press the gas until the engine stops at around 3000 RPM.

When I drive in the city I lightly hit the gas from a light and the engine goes immediately to about 2500 RPM and stays there for a second while the car accelerates a bit then engine RPM starts to climb proportionally to the cars acceleration.

There is also what is called flash RPM - this is the RPM that the engine climbs to if you are stopped with engine at idle and suddenly open the throttle. My torque converter actually flashes to 3300 - 3400 RPM (if the tires don't break loose . . . hehehe).

Hope this helps

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68 Camaro, 383 small block with TH350 trans. 12.2's and never trailered.

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Oct 14th, 01, 09:48 PM
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Larry