What tranny do I have?

I'm a fairly new member here and trying to determine what automatic transmission is in my '68 Skylark. It is supposed to be all original (no reason to doubt that it isn't) with a 350-2. What would have been the stock tranny for that year? Or were there more than one AT available and if so how can I tell which one it is? This is my first foray into the world of Buicks so trying to learn these things. Thanks.

Tom

 

Hi there, your car SHOULD have a ST-300 2 speed trans. This trans has a 1:1 gear ratio so that means that on the highway the engine is turning the same RPM as the driveshaft. The th350 and th400 are the 3 speed trans than the later Skylarks have and they also have a 1:1 ratio in top gear (3rd), what these trans have as an advantage over the st-300 is better off the line acceleration due to the extra gear.

Many people swap the st-300 out for a th350 as it is a bolt in swap pretty much.

Here is some info about it:

http://en.wikipedia.org/wiki/Super_Turbine_300

ba

 

Thanks for the reply and the info. The wiki link is now in my "favorites". Really liking this forum.

Tom

 

Glad you found the info useful.... Just be carefull with wiki as not all of the info is 100% correct... It is a great way to find general info just be sure to confirm with us on here before you take it as gospel.

I know you may not need this much info, but here it is in case you do want it LOL!!!! :TU:

Some more info you might find usefull:

Even though it is called a ST-300 is comonly refered to as a Switch Pitch or SP-300.

The ST(Switch Pitch) 300 has the AWSOME advantage of having the best of both worlds when it comes to the torque converter. The reason the SP feature is great is it allows for better torque multiplication when getting the car off the line. You can think of this as a controlled amount of "slip" in the transmission which allows the engine to rev up quickly and effortlessly as the car leaves from a stop. This is kind of like revving up a manual car and dumping the clutch, the result is quick accelation only it is a smooth and not jerky with the SP trans.

The only downside to this trans is that it only has 2 gears.

One of our members took a 300 cubic inch Buick powered car with a SP-300 and ran it in the quarter mile. Then swapped to a th350 and gained a MASSIVE amount of time, I think it was almost a second quicker in the quarter mile with the 3 speed trans.

So the bottom line is that although the SP is a great feature the fact that it is a 2 speed trans puts it at a disadvantage compared to the 3 speeds.

For more info on how the Switch pitch works:

http://www.buickperformanceclub.com/SPTrans.htm


I am using the SP-400 trans in my turbocharged Skylark as it is a great feature! The 3 speed SP-400 is basically a heavy duty trans like the TH-400 but it has the variable pitch converter like your trans. I find this useful for my car as I plan to drive it a lot on the street and will enjoy the low stall setting as it will keep the MPG up and reduce engine and trans temps. Then when I am at the track racing the high stall will allow the car to get off the line really quick due to the extra torque multiplication.

I will run my Switch Pitch converter off a toggle switch on the dash and that way I can pick which I want. The factory setup is in high stall when you leave the line or stoplight and then low stall when you are cruising. The system works well when things are new however over the years it comonly has issues and stops working as it is designed to. It is not normally the trans that has the issues it is the electrical connections that cause the problem. So many people either add a toggle switch to control the switch pitch or buy an aftermarket box (Bruce Roe sells it) that automatically turns the converter to low stall after the car leaves the line. For drag racing this box is great because you can adjust the amount of time you want the high stall to be acticated. Typically we set the box to be in high stall mode for 1 second and then after that it is in low stall till we come to a stop.

 

Sounds like a nice set up. I'm really liking the Buick but I've got alot to learn and will definitely check here first. Thanks.

---------- Post added at 05:44 AM ---------- Previous post was at 05:43 AM ----------

Good to know. Thanks.

 

Thanks for catching that Larry!

 

The best way to tell is to crawl under there and take a look. The tranny oil pan is the easiest way to identify a tranny. I don't have a handy link, but there are many online references for identifying trannys by their pan shape.

This site can be a life-saver, so don't be afraid to ask for help. And spend some time searching and reading about stuff.

Good luck :TU: