So with all the questions going on I figured I post up this thread as more of a knowledge thread when it comes down to those of us looking to improve how our power is getting to the ground and just as an FYI for those just curious about what can be done to improve it. Please only post information that is based on facts about our trucks and the transmissions in them or relative to any questions asked in this thread and not personal opinions.

I'll start with a few questions I have had for a while now that I am looking to install my new TC soon...

- How do TQ Converters and the OD on our transmissions work together? Basically why is the stock TC set to 2300rpm when at stock cruising at 65-70mph my engine rpms were well below that around 1900rpm? Even with 4.56 gears the rpms are just below that at 2200rmps which leads me into my next question...

- Is the TC only for acceleration or should it be active or "locked" at cruising speeds? When just cruising around town Im barely above 1500rpms so its technically slipping and not locked when cruising on the highway Im barely under it right around 2200rpms so its still technically not locked. Now accelerating is an entirely other story as I see the upper 3000rpms in the city and on the highway while accelerating. So really the ONLY times it would be "locking" is during acceleration, and thats with the stock converter.

 

torque converters arent and "on" or "off" thing. at a given RPM, the motion causes internal structure of the converter to drive the transmission. at varying rpms, the fins inside the transmission rise and fall to allow a certain amount of what you are calling slippage. this is why you can sit in gear, idling, and the truck wants to move very little, or not at all...because at idle there is not enough force to engage the converter. at highway speeds, youre creating enough rpm to make power, but id bet that if you watch the tach closely and you hit it at highway speeds, the rpms will spike a little before the truck starts to pull.

in the case of a stock converter, it doesnt take much for it to engage, but with high stall units, it takes more rpm/effort by the engine. however, say that you brake stand the truck and it takes 2300rpm for the tires to spin or for the truck to shove itself forward. then you do not brake stand it, and just pull out normally...you should be moving way before 2300rpm, as at lower rpms the converter is sending power to the transmission, but not full power...until you hit the rated rpm. i have a 4000 in the mirada and a 3000 in the demon, but under normal driving in the demon, the car is moving out around 2000rpm. i dont recall where the mirada moves out without braking it a little.,..but in normal traffic the mirada sounds like a manual transmission with a slipping clutch as it makes alot of rpms before it moves. with the mirada at cruising speeds...if i let the rpms drop to say, 2500, and then hammer it...it "bangs" the converter, and will generally spin the tires at a roll...

i dont know that the higher stall is strictly for acceleration, although thats all ive used them for. keep in mind that your engine makes peak power within a certain rpm range. for the mirada, its 3500-6500...so if im launching at 3000 rpm, i have to move through about 500rpm before im into my peak powerband. however, with the 4000, im launching at peak power and it makes an incredible difference.

 

The stall speed, is the speed at which the torque converter will lock up,hydraulically, under load. Things that need considered are weight, torque, gear ratio and tire size as all these things will directly impact the stall speed. A torque converter may be advertised as 3500 rpm stall, but this is just an estimation, or ball park figure. A torque converter will act differently in different vehicles.

A torque converter, at part throttle or cruise, is not under major load, as momentum is already helping the vehicle, so the converter will lock up below the advertised stall speed. Thats why "stall" converters still work fairly well on the street, without causing over heating problems in the transmission.

Think of a stall converter like a clutch in a standard transmission, rpm's have to rise to get the vehicle moving initially, after first gear, the rest of the shifts take place without having to run up engine rpm. A stall converter works the same way.

A stall converter will lock up at lower than advertised stall, but when put to the mat, the converter will do what it is designed to do. Allow RPM'S to rise to the lock up point to allow vehicles to accellerate while in the middle of the torque curve instead of the bottom of it.

Edge converters are the shizzle for HEMI's, these are custom built for YOU'R application. They even want to know what mods you have so that they may perfectly match the application. Take a look. I can tell you from experience that these converters are worth every dime!

http://moesperformance.com/index.php...oducts_id=1453

 

Thank you guys, that was exactly what I was curious about, I just was not sure as to what TC did at cruising speeds since the engine rpms are well below what the stall is on both the stock TC and my APS TC. I will be installing a new trans cooler off a 2500/3500 and a trans temp gauge when we install the converter to keep things cooler.

One last question, I have also heard that with a new TC it is best to install a transmission reprogram kit as well like the kit from transgo. Is this a necessary thing to do or with the DSP be able to handle the new TC with its trans tuning options?

With the new cam going in shortly I really want to be able to get as much of that power to the ground as possible and keep it relatively streetable at the same time.

 

A trans-go shift kit is an awesome addition. it will make the draggystock shifts much more crisp. It is not a necessity, but it would help

 

So for race applications, I understand its best to go with a higher stall speed. For efficiency's sake, would it be better to go with a lower stall speed (i.e 1800 or 1900)? Would a lower stall speed adversely affect acceleration, rwhp, mechanical wear, etc.?

 

So for race applications, I understand its best to go with a higher stall speed. For efficiency's sake, would it be better to go with a lower stall speed (i.e 1800 or 1900)? Would a lower stall speed adversely affect acceleration, rwhp, mechanical wear, etc.?

 

A lower than stock stall will decrease the engine's ability to build RPM when accellerating, but stockers are pretty bad about a small amount of constant slippage. even replacing a stock converter with exactly the same stall speed will be more efficient than the stock ones. But I wouldnt reduce stall speed from stock.a converter that locks too quickly will cause the engine to bogg down.
With the higher stall (within reason) an aftermarket converter will allow the engine to get well into the torque curve before it locks up. This keeps the engine from "lugging" at lower RPM's

 

4 wheel drives and vehicles used primarily for towing often used converters with lower than stock stall speeds. These converters are more efficient than stock and are also built stronger to take heavy use. I had one in a truck I used for hauling my travel trailer in the mountains and deserts of California.

 

but any time the TC is slipping, its not being 100% efficient, correct? I'm rarely above 2500 rpms. I guess I dont understand why one would want the TC to lock up later in the rpm range. If its locked at 2100, its gonna be locked at 4000 too, right? Seems to me like it'd be best to get it locked up ASAP so its the most efficient in the transfer of power from the engine to the wheels