65GS.com - Buick Gran Sport Enthusiasts!
Drivetrain => Transmissions => Topic started by: moteaux on November 20, 2020, 09:22:39 PM
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I converted my GS from a ST300 to a TKO 600 5-speed manual transmission. I also replaced the rearend with 4.11 gears. The differential and transmission gear ratios combine to shift in the sweet spot of the 401 torque curve. It's a combination that is a lot of fun to drive.
I ordered most of the components for this conversion from American Powertrain. The top of the TKO 600 is specifically modified to fit a GM A-Body. And it fits perfectly.
Some part numbers for reference:
- TREMEC TKO600 Part Number: TCET5009
- Bellhousing: Quicktime Part# (RM-6017); I had to make some minor modifications to the bell for the installation.
- Pilot Bearing (without bushing): AC Delco 14061685 or Dorman Bearing Part No:690-057
- Flywheel: ScienceFriction 11’ FWBU-10002
- SCIENCE FRICTION 1126 STAGE1 SUPER STREET Pressure Plate and CLUTCH
- HYDRAMAX Hydraulic Clutch: HMGM-01101G
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I provided American Powertrain with the dimensions of the crankshaft pilot bearing relief area and they fabricated a bushing with a pilot bearing for a nice interference fit.
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I had to make a minor modification to the transmission tunnel.
The shifter knob was custom-made by https://www.twistedshifterz.com/. (https://www.twistedshifterz.com/.)
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Some pics of the Hydramax hydraulic clutch. I have a 2015 Camaro SS with a Tremec TR6060 6-speed to compare to and the Hydramax compares very well for clutch engagement and pedal feel.
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Some additional pics for reference. The GS stock crossmember can be used for this setup. However, I elected to replace it. American Powertrain cut and balanced a driveshaft for the new length and yoke/U-joint requirements.
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Moteaux, thanks for the very informative post. Well done.
Dan
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By my calculations, a 22-tooth driven gear would have been ideal for this configuration. But, my options were a 21 or 23-tooth driven gear. As best I can tell, a 22-tooth driven gear for my TKO style drive gear does not exist. I opted for a 21-tooth driven gear. Using my 'calibrated' phone app speedometer, the GS speedometer reading is very close to actual speed (+/- 1mph).
Tremec TKO 600 Drive Gear is 7 teeth (Yellow)
65 GS Calculation: (7 x 4.11 x 775)/1001 = 22.27 driven gear
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Moteaux, thanks for the very informative post. Well done.
Dan
Thank you, Dan. When I decided to do this conversion, I did not find an internet resource and reference for a 65 GS TKO conversion. So, I took a lot of pictures and made notes along the way to post to this forum as a future reference for anyone interested in doing the same.
Marty
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The GS gained 66 lbs. in this conversion. Here are some weight references:
Transmission Conversion (ST300 to TKO 600): +14 lbs.
Rearend Conversion from a stock 10-bolt 3.08 to a 9-inch 4.11 Eaton TrueTrac Posi: +48.4 lbs.
Driveshaft: +3.4 lbs.
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Thanks for the great information! I am pondering a 5 speed for the 66 GS convertible which is now a 4 speed. I wonder if this could be made to work still keeping my factory consolette. For interstate driving and long trips I either need to add an overdrive to at least one of the cars or change one to a 2.56-2.73 type gearing.
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Moteaux, thanks for the very informative post. Well done.
Dan
X2
Loren
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X3!
Chuck
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Thanks for the great information! I am pondering a 5 speed for the 66 GS convertible which is now a 4 speed. I wonder if this could be made to work still keeping my factory consolette. For interstate driving and long trips I either need to add an overdrive to at least one of the cars or change one to a 2.56-2.73 type gearing.
I believe it will work, but I do not have a consolette to test fit. I installed a White Lightning shifter to the TKO. It's a nice and tight shifter, but not ridiculous. And more importantly, it is adjustable in several directions. I would be surprised to learn if you could not make it work with the factory consolette.
I selected a standard A-body location and tried to show the modification I had to make to the automatic tunnel hole location. Hopefully, the attached pictures and the adjustability of the White Lightening shifter can help you determine if it is worth attempting.
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Thank you moteaux for providing such a nice explanation of your transmission installation! (http://www.canebas.org/WeatherCat/Forum_support_documents/Custom_emoticons/thanks_sign.gif)
Cheers, Edouard :occasion14:
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Yes, this is great information! Thank you!
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Great info and well presented. It will be a completely different ride.
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Greetings Marty
How is this going? I'm curious about how the 4.11 gear is working. I'm torn between the 3.42 and a 3.91 for my Tremec conversion on a 65 Wildcat.
3.42 is in the car and I'm about to try it out finally - started this in like 2003.
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My selection of gear ratios--transmission and rear end--were based on the 401 torque curve. I love the low RPM high torque of a 401. Said differently, I love the drivability of a muscle car with max torque at a low RPM. And the combination of a TKO 600 with a 0.64 OD gear and 4.11 rear end gears is nothing but pure fun around town. It is also a ratio combination that makes interstate driving reasonable and practical. In hindsight, I would not change anything. Therefore, I recommend you go with 3.91 gears.
You will hit the max torque of a 401 at ~2,800 RPM. Your tire height matters. I used my tire height (255/45 R17 = 26.04in) and the rear end gear ratios your considering for the calculations below. I used the Tremec Toolbox App to do this.
Pic 1: Tremec Tool Box App
Pic 2: 3.42 rear end gear with a TKO 600 (0.64 OD Gear)
Pic 3: 3.91 rear end gear with a TKO 600 (0.64 OD Gear)
I would get the Tremec App or find a calculator to play around with gear ratios to fit the kind of driving you would like to do with the car, keeping in mind the 401 torque performance curve.
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Greetings Marty
How is this going? I'm curious about how the 4.11 gear is working. I'm torn between the 3.42 and a 3.91 for my Tremec conversion on a 65 Wildcat.
3.42 is in the car and I'm about to try it out finally - started this in like 2003.
The difference in first gear will be noticeable.
Your 'First gear starting ratio' is 1st gear multiplied by the rear ratio:
2.87 first x 3.42 rear = 9.8
2.87 x 3.91 = 11.22
General recommendation is around 10:1 for a street car.
A 9.8 ratio is ok, might have to slip the clutch a bit to get the car moving.
A 11.22 ratio would get the car moving from a stop easier but it will be a short first gear.... you'll have to shift into second at a slower speed.
You're likely running tall tires which will affect the above a little.
At the other end, compare your highway speed/rpm to see which works better for you.
You have some other stick cars, so do that 1st gear calculation on those for comparison.