Originally Posted by yjJEEPyj
This is prolly a dumb question.. What happens when you get the wrong converter? Rpm's all over the place?
Its actually a good question, and one I should have asked myself when I did my swap.
Its not the easiest thing to explain but ill do my best.
Your Torque Converter has a "Stall Speed", Stall Speed is the engine RPM level at which the Torque Converter "locks" and overcomes whatever resistance is present to turn the wheels. [Weight of vehicle, brakes being on, ect.]
Ok so your Stall Speed should be at the RPM at which the engine has its peak torque.
-So, what can happen is (and happened to me) becuase the Torque converter in that Chevy is dialed in around the Wieght of the truck, once installed in your much lighter Jeep it will lower the Torque converters stall speed. Becuase the Jeep wieghs less, there is less resistance to overcome to gain lock up.
Since your not at your peak torque your wasting potential power by 'locking' in to early. All that wasted power turns into heat, and heat will basically destroy your torque converter, and transmission, not to mention cuase transmission slippage.
How I found this out:
I didn't know any of this when I did my swap and just bought one off the shelf that fits a TH350. Well with a light Jeep coupled with my beefed up 350 my stall speed was way way to low. For one I really have to press the brakes hard at a stop, (I've actually taken to shifting into neutral at stop lights, yeah that bad). The other effect is slippage at higher rpms. So basically after just maybe 20k miles my tranny is shot.
Hopefully all this didn't fry your brain!
Here is a exert from an article about what info you need when calling to find out what TC you need.
Be honest with yourself and decide how you want to use the car. Most of our own cars are 80 percent street driven, and 20 percent track abused. Given this information, the converter tech guy would suggest a converter that retains good street manners. If you tell the tech guy your street machine is “100 percent race car,” but you’re really intending to drive the thing on the highway, you’re only setting yourself up for disappointment.
After you’ve declared your intent for the car, you also need to tell the tech guy the weight of your vehicle, and the following information about your powertrain combo:
• Compression ratio
• Cam profile (duration at 0.050-inch lift, lobe separation angle)
• Carburetor or injector size
• Transmission model year and gear ratios
• Rearend gear ratio