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#1
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66 auto trans option
Did all 66 Automatic gto’s Get the ST300?
I haven’t looked to verify what is in the car, but figured since the engine is out it might make sense to have the Trans rebuilt. If it has the ST300 is it worth rebuilding or should I switch to a 350/400? |
#2
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Yes. All '64 thru '66 GTO's.
Most guys prefer a 3-speed auto. If you ever plan on big power, go with a correctly built TH400. For bracket racing, I'd actually prefer a 2-speed. My trans guy said he can build up an ST-300 for bracket racing. But, for street driving, a 3-speed will make the car feel more spunky. Don't figure very many guys stay with the 2-speed, unless they are doing a numbers matching resto. Last edited by ponyakr; 11-27-2019 at 12:48 AM. |
#3
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As said above, the ST-300 was the only automatic installed in the '66 GTO. The TH-350 is a direct bolt in and even uses the same driveshaft. You'll have to tinker with shifter linkage and kick down cable, of course.
The first gear is so much lower than the two speed, it'll feel like you picked up 50 horsepower. Much recommended swap!
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1966 GTO 1969 Lemans Convertible- F.A.S.T. legal family cruiser. 12.59 on G70-14 Polyglas tires. 1.78 60' 1969 Bonneville Safari- cross country family cruiser. . 1979 Trans Am 400, 4-speed, 4 wheel disc. View from the drivers seat racing down Atco Raceway- http://www.youtube.com/watch?v=GhYDMdOEC7A Ride along in the other lane-http://www.youtube.com/watch?v=mIzgpLtF_uw |
#4
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We switched to the TH350 in one day, it was so easy. What a difference off the line. Just had to add the kick down cable, which was simple. .
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#5
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Hmmm..... I have the TH 350 out of my 72 Firebird. Maybe it makes sense to have that rebuilt.
Would it be best to swap in a 67 shifter? |
#6
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I installed a TH350 in my 68 Tempest & used the 2 speed column shifter w/no mods to it. If you have a floor shifter you may have to make some changes to it.
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#7
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If you are going to modify it from stock you mind as well go with the 700R4 overdrive. The car will be much better on the open road and the lower RPMs at crusing speeds result in much less wear & tear on the engine.
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#8
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If you have the 350, freshen it up and bolt it in. As others have said, it will entirely transform the car. You'll feel like it has another 50-100 horsepower. MUCH more responsive, and a bolt-in deal.
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Jeff |
#9
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You can buy the kit to modify your 2 speed shifter from Shiftworks. The TH350 is the way to go if you already have the trans
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The More People I Meet, The More I Love My Dogs! |
#10
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Thanks guys- I drove the Firebird with this Trans in it so I know it’s at least a good starting point. My neighbor works at a transmission shop so I can have him go through it.
Do I need to change the crossmember? |
#11
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A couple of my friends did the 200R OD conversion.Tom
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#12
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Quote:
You’re going to need a dipstick and tube that’s compatible if your current tube hits the firewall, which is likely. You’ll need to source a factory assembly from an A-body that was originally equipped with a TH350. I’m about to swap a TH350 into my ‘64 Le Mans. I have a TH350 dipstick and tube from a ‘76 T/A that surely will interfere with the firewall after putting it in place to check. I sourced a good used ‘70 Tempest dipstick assembly that hugs the engine and trans much more closely, crossing my fingers that it will work when I get around to installing the engine and transmission.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#13
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You're right about that dipstick tube. I tried three of them before I got one that fit. I believe that it was an original from a '69 Chevelle.
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#14
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Well I had the shop pull the trans out and it looks like someone had already done the turbo 350 swap. That’s good cause I can have it built at my neighbors shop and everything should go right back in.
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#15
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Nice, that was easy!
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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