I have a 1965 Buick Special Deluxe Wagon, and while its fun to drive I would like for it to have better hwy manners. Seems the gas guage moves easier at hwy speeds. I need to reseal the transmission in that it leaks pretty good, so Im wondering should I even bother with it, or replace it with something else, and if so, with what?
Swapping the ST300 for a TH350 isn't going to change a thing on the highway, high gear is 1:1 on both transmissions. Sounds like some more diagnosis is in order. What's the rear axle ratio in your '65? Are you familiar with the ST300's variable pitch torque converter? If so, can you confirm that your ST300 is in low stall mode at part throttle cruising speeds? Devon
A TH-350 will help tremendously as it has 3 actual gears to use and the ratios are split up well. The ST-300's high 1st gear ratio (1.76:1 I believe) is poor for both economy and performance. I highly recommend the swap, and have done it myself several times; on all of my ST-300 equipped cars. Now if I could just find a use for the 4-5 ST-300's I have laying here.
I dont know of the axle ratio. The tag is still on it, I just havent examined it yet. It is a positive traction rear end though, and powered by a 355 Wildcat. As for confirming the low stall mode at part throttle, it seems to shift right, (with what limited experience I have with it, which is about a month of driving it and this car is 9years older than myself) I just think it could use another transmission gear for better hwy manners.
If you're trying to reduce rpm on the highway, you'll have to install a later model transmission with overdrive, change rear axle ratio, install taller rear tires, or any combination of the three. At least knowing the engine rpm at say, 60 mph and tire height can help us figure out what rear gears you've got. Devon
The 355 is the 4 barrel 250hp engine. That may have a 3.23 rear end in it for performance. I would check the rearend ratio first.
Have you tuned up the car? I would do that before started changing transmissions. You can get 16-17 mpg out of those cars in stock form. Most important thing for fuel mileage is to check that the vacuum advance is working. If not, it will kill your fuel mileage. Also check the ignition timing and set the point gap to specs.
A/C cars had a taller diff gear in them from the factory....I think you can wire brush the diff case off in the area of the bottom of the pumpkin and the code of the gear ratio will be stamped on it... a 93 will be A 2.93,,,, A 08 will be a 3.08 and so on.... 23 would be a 3.23.... a circle with a x in it will be a posi....
The original owner kept up with mileage and the amount of gallons per fill up. Averaging those numbers out it seems the car gets around 13 mpg. I have a lincoln towncar that gets around 21 driven right, and I was wondering if something comparable could be accomplished with the wagon. I have tuned the motor and set the timing. The car runs great and is fun to drive. You can really tell there is alot of torque, and being that the RPMs arent ever really low there isnt much hesitation to tapping into the power curve. I looked at the rear end, and what tag was on it referenced what type of diff lube to use. A closer examination revealed some numbers. Looking at the input of the diff, located at the 10 o'clock position was /357\, at the 8 o'clock position 1869829 and at the 4 o'clock was CFD 1.
Probably even better than that... My 65 Sky convertible with a passenger and a trunkfull of stuff got 18mpg on the highway recently (Tacoma to Vancouver) and I don't consider it to be tuned as well as it could be. I have a TH350 but the mpg was measured on highway driving only, so I believe the gear ratio is the same as the ST300.
The wagon will always have worse mileage than the regular car since it weighs alot more, so keep that in mind. When you did the tune-up, did you check to make sure the vacuum advance was working? Most all of the wagons had a 3.23 rear end, so one way to help the mileage would be to swap in a 2.78 rear end from a regular skylark of the same year.
My understanding is they are looking for a st 300 vairable pitch for the Renyolds car. http://www.v8buick.com/showthread.php?t=213623
If you're going to swap trannies I'd suggest a 200r4. One with a dual bolt pattern bell housing would be a drop in. That way you'll get OD as well as a lower first gear. Personally I liked the ST300, even tho 1st gear was only 1.76 to 1 with the switch pitch torque multiplication was quite high.
