Turbo
Tek Toys' Home
Tips! Contents
Tips! Search
Is the C3 auto tranny weak?
Category: Drivetrain
The C3 is not weak. Most people just hop up cars with over 100k miles on them and don't perform adequate maintenance. Then they declare the tranny was weak when it breaks. Sure it was weak, it had 100k mile old fluid in it. They rarely rebuild it properly, and maintain it therafter. If they had, they would still be driving on it. It's very popular to swap in a manual transmission. Doesn't make sense to me, but that's what usually happens.
The C3 should take 250 hp or more in top shape. That's an off the top of my head guess, but I know that A4LDs can be built to take 400 lbs of torque and it's the same transmission with an overdrive.
Here's a few things that will make it last longer:
If the radiator is not new or recent, bypass the in-radiator cooler for the auto trans. If it leaks and you get coolant in your tranny fluid the tranny will need to be rebuilt. When you bypass the internal cooler, install a LARGE external auto trannny fluid cooler. I'd remove the stock external cooler in the interests of simplicity.
Never power brake an automatic transmission. Figure you're taking 5000 miles off of the life of the transmission every time you do it. And that's with a new tranny with a lifespan expectancy of 100k miles. So about 20 times power braking it and it will soon start to slip. If it's used, and has some mileage already on it, you're playing russian roulette.
Change the fluid and filter, clean out the pan. Every 20 K miles. Just use the specified fluid, no need for additives.
Make sure that the cable is properly adjusted so that the tranny shifts quickly and cleanly under WOT at about 5200 RPM. If the shift is slow, it's burning up the bands.
Make sure the vacuum modulator is in good shape, and not leaking fluid. Pull off the vacuum hose to it, to check it. Check out the condition of that line also.
Make sure the cooler lines are in good shape, and not leaking fluid.
Check the fluid regularly for a drop in level or a burnt smell. The fluid should be a clear red color, not brown, milky, or opaque. Fluid is the blood of the transmission, if the blood is bad, it's dead.
Transgo makes a good shift kit for the C3 that works well, just make sure to NOT follow the directions regarding the check ball installation in the reverse circuit or you will not have a reverse gear. I have been told it costs $12. For that cost, this is a terrific mod.
I recommend you become familiar with your transmission by doing the mods and performing the maintenance yourself. This will get you familiar with it, and hopefully prevent a visit to a professional.
If worst comes to worst, the soft part rebuild kit from NAPA is about $75, and you can do it at home, with a $20 book. The hard parts very rarely break.
The only negative to the C3 is that it doesn't have an overdrive and a modiied XR will reach 100 in a hurry. At 110-120 MPH, somewhere in there is the redline, and it's just no fun screaming down the highway at 5000 rpm when cruising fast. For a fun car to drive around and back and forth to work, a modified XR automatic is a total blast. Exhaust, boost bleed, maybe later an intercooler and cam, and it'll surprise the hell out of ya. You might get beat for the first 50 feet, but after that, you are gone. :) It's no trouble to wax a vette or other much more powerful car out on the freeway.
All these tips and statements apply to a street driven car with street tires, not a dedicated drag racer with slicks. If you are racing alot you will break it sooner. But you will be very surprised at how long it lasts...