info transfer from "parts for sale" . older , hopefully acurate info that may help somebody out . will try and type "as printed" . from sept 1992 car craft magazine page 110 , "tech talk" question and answer section . del title : gm's other two speed question : "i have a '68 buick lesabre with a 350 engine mounted to a super turbine 300 two speed automatic with a non variable pitch torque converter (also used in the gs350 , skylark and special) . i would like to know if anyone manufactures a shift kit or high stall speed converter for this transmission . (signed) - dave rupe indianapolis , indiana answer : an excellent trans and inherently much stronger than the common powerglide (pg) , gm's super turbine 300 (st300) was used from '64 - '69 in selected buick , olds and pontiac applications . instead of the pg's 17 spline input shaft , the st300 has a th350/400 type 30 spline input . an st300's clutch hub is similar to a th400's so it won't break like a pg's . compared to a pg an st300 also has stronger planetary gears and a 1.82:1 low gear (most pg's use a 1.76:1 low except for the weak 1.82:1 6 cylinder versions with stamped steel planetaries) . some st300's even had variable pitch stators like the "switch pitch" th400 , but because of parts scarcity its hard to convert one originally not so equipped . most st300's used the "b-o-p" (buick , olds , pontiac) trans to engine mounting bolt pattern , but '67 - '68 pontiac ohc 6 cylinder versions came with a dual bop/chev mounting pattern . original st300 flexplates were drilled for the small 10.75 inch torque converter mounting bolt pattern and will accept pontiac style th350/400 converters (where the converter mounting lug has a welded on nut for the converter mounting bolt) . by changing to a th350/400 dual bolt pattern flex plate (available for most engines) they'll accept any th350/400 type converter . no off the shelf shift improvement kits are available . darrell young transmissions (7250 hinds ave , north hollywood , calif 91605 - 818-503-9055) sells adjustable vacuum modulators for firmer harder automatic and manual shifting . darrell can also play with the governor springs and weights (lightening the the weight or using softer springs raises the automatic upshift point to a higher rpm) but you might want to try this yourself as the exact results of any off the car lightening are only a guess . governor weights and spring are unique and not shared with any other trans . you can also drill a hole in the valve body plate as shown in the photo . for all out competition darrell can build an st300 full manual valve body out of an existing valve body or custom build an air operated manual trans brake . because of its strength the st300 works great behind big blocks in those applications where a two speed powerglide style trans is normally utilized ." thats all . remember this is older info so ---? i could not obviously type the photo in but what it showed was the valve body seperator plate : looking at the bottom of the plate , front of the plate facing 3:00 o'clock , at about 10:00 o'clock there are what looks like two small holes and just to the right there are three longer slots and one slot that is about half as big . they say to enlarge the second hole in to 1/8 inch for street use and 5/32 for race use . just a little info to maybe keep that race buick all buick . del
That's pretty interesting... certainly showed me, eh? :beers2: Maybe I will actually look into what is so horrifically wrong with mine instead of looking for an upgrade just yet.
like i said , that is older info from just one source . probably (?) more useful now in terms of a race oriented vehicle , certainly not a gas mileage vehicle . and remember some magazine info gets translated/handed down/incorrect on occasion . but either way it sounded kinda interesting and may come in handy for someone . del
FWIW: Back in the day (late 70's, early 80's), before the arrival of the aftermarket parts for the PG, the trick was to canibalize a TH-300 for several parts for strength. I have a book, somewhere, that shows how to do this, but I have not built a PG in maybe 20 years. Jim
