Author Topic: Automatic transmission help  (Read 1784 times)

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Offline 65GSVERT

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Automatic transmission help
« on: November 12, 2012, 12:07:28 PM »
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:
1965 Skylark GS Covnertible

Offline Brian

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Re: Automatic transmission help
« Reply #1 on: November 12, 2012, 01:15:29 PM »
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.
'64 Skylark 2dr ht 4 speed, 300-4
'65 GS ht, 4 speed,2-4s,AC,PS,PB,PW,Pseat,Tilt
'66 Skylark 2dr ht 300-2 automatic
'78 Yamaha DT 400 2 stroke
'88 Ford F-150 4x4 (used to be 4x2)
'89 Ford F-350 4x4
'03 Honda Accord Coupe V6 6-speed manual (daily driver)

Offline dsags

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Re: Automatic transmission help
« Reply #2 on: November 12, 2012, 04:06:23 PM »
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/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 ?
1965 Gran Sport 4 speed Convertible, BCA Sr Gold
1965 Gran Sport Hardtop

Offline 65GSVERT

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Re: Automatic transmission help
« Reply #3 on: November 13, 2012, 08:03:52 AM »
3.55 would be great. If I went with the 200r4 do I need to move the cross member or do any other modifications?
1965 Skylark GS Covnertible

Offline WkillGS

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Re: Automatic transmission help
« Reply #4 on: November 13, 2012, 09:57:39 AM »
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
Walt K
Eastern Pa

66 GS Astro Blue/blue 425 auto
66 GS Silver Mist/black 401 4 spd
66 GS Flame Red/black 401 5 spd
66 GS Saddle Mist/black 401 L76 auto
66 Special Flame Red/black 300 5 spd
65 GS vert Verde Green/ Saddle buckets 401 4 spd
79 Turbo Regal

Offline dsags

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Re: Automatic transmission help
« Reply #5 on: November 13, 2012, 11:13:25 AM »
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 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.
1965 Gran Sport 4 speed Convertible, BCA Sr Gold
1965 Gran Sport Hardtop

Offline dsags

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Re: Automatic transmission help
« Reply #6 on: November 13, 2012, 11:14:44 AM »
Last three pages of the article
1965 Gran Sport 4 speed Convertible, BCA Sr Gold
1965 Gran Sport Hardtop