93GTDIN,
What does a shift kit do?
A quality shift kit will change the way fluid flows through the vavle body of your transmission. This is accomplished by changing some springs and valves. Transgo makes one of the best kits out there.
How hard is it to do?
It really isn't all too difficult of a mod. The kit comes with a video and written instructions that walk you through each part. You'll have to pull the valve body off the car from underneath, but that's not bad, either. After that, its step 1, step 2, step 3....
Why do you need a shift kit?
The stock AOD is a relatively weak tranny for performance purposes. It has smallish bands and clutches, and shifts are slow and light. The slow shifting characteristics mean that more time is spent in "slip" between positive gear engagement. This long period of slip puts extra strain and wear on the inherently weak bands. A shift kit changes fluid pressures and flow in the valve body causing the tranny shifts to be quick and firm. Less slip time = less wear and better performance.
A Transgo kit will set you back about $110, but it is essential for AOD trannies. You'll love the confident shifts and it will cut time off of your et.
As far as the rest of the tranny goes, to make it run, you're going to need a torque converter that stalls around 2500-2800 rpms (works basically like the clutch on a 5-speed, linking the flywheel to the input shaft of the tranny). The stock unit stalls around 1500 rpms which is a bit to low for the 302's powerband.
In case you aren't familiar with it, stall speed is where the converter directly links the flywheel and input shaft in a 1:1 ratio. Before this number, the converter slips and multiplies torque through fluid dynamics. This characteristic allows your engine to reach stall speed very quickly. Go out in your car and sit at idle. It should idle near 800-900 rpms. Then, take off quickly and watch the rpm's jump to around 1500 almost instantaneously. This is call the
flash stall speed and is very close to actual stall speed. Some people tell you to find it by holding the break and reving the engine until you move, but that is not accurate as the breaks will not hold the car still until actual stall speed is reached.
For an AOD to perform with a 5-speed, it takes a set of gears (3.73's or 4.10's), a good shift kit, and a good converter all of which work together to get your engine into its powerband as quickly as possible.
That's my lesson for today on basic automatic drivetrain. If you have any questions, let me know.
--nathan
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--silver_pilate
'91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods...
Tried and True 302 Being Built to Outrun You! heh heh heh...
--Texas Panhandle--
Check out my site