65GS.com - Buick Gran Sport Enthusiasts!
Drivetrain => Transmissions => Topic started by: 65GSVERT on November 12, 2012, 12:07:28 PM
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Ok, I have been trying to do my research but am getting very confused. I want to put some taller gears in my 65GS, 3.55 or so. The car is an automatic with the 2.78's in it. I would like to upgrade to an overdrive transmission or at the very least a 3 speed. What are my options? :tongue3:
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There are no overdrive transmissions that will bolt up to the nailhead engine. Your only options are to add a gear vendors overdrive to your current ST300 transmission, or install a ST400 out of a 65-66 Wildcat/Electra/Riveria. Installing the ST400 requires moving the crossmember rearward and modifying the welded-on mounting brackets where the crossmember bolts to the frame.
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Doesn't Bendsten's make adapters to mate various transmissions to the nailhead ?
http://www.transmissionadapters.com/53-66_nailhead.htm (http://www.transmissionadapters.com/53-66_nailhead.htm)
http://www.transmissionadapters.com/transmissions.htm (http://www.transmissionadapters.com/transmissions.htm)
If you can put a 200R4 behind the nailhead a change in gears would probably be necessary with the .67 OD. What would be required to change the gear from the 2.78 to a 3.55 ?
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3.55 would be great. If I went with the 200r4 do I need to move the cross member or do any other modifications?
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To install 3.55 gears you would have to replace the carrier as well... Buick used 3 different carriers depending on gear ratio:
1) 2.56 and 2.78
2) 2.93, 3.08, 3.23
3) 3.55, 3.90 and 4.30
There are aftermarket posi carriers avail. Jim at JDrace.com is a Buick guy that can set you up. :thumbsup:
Moving the crossmember back isn't too complicated. Best to weld on new frame brackets, but it can be as simple as bolting 2 pieces of 2.5" (approx) angle iron to the frame.
A shorter drive shaft will be needed. Parking brake cables need to be modified or replaced.
A shifter conversion is avail from:
http://shiftworks.com/buick.htm (http://shiftworks.com/buick.htm)
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This conversion would not be inexpensive. Do not know what the gear change would cost but the 'official' price at the Gear Vendors site http://www.gearvendors.com/hrgm3s.html (http://www.gearvendors.com/hrgm3s.html) is $2,695. For the 200R4 you would need the transmission and the adapter plus some other parts. Here is an article on the swap I had. Note the swap is into a 67 Skylark. It does not have a nailhead in it.
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Last three pages of the article