65 GS TKO 600 5-speed Conversion

[moteaux]

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

[moteaux]

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.

[moteaux]

I had to make a minor modification to the transmission tunnel.

The shifter knob was custom-made by https://www.twistedshifterz.com/.

[moteaux]

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.

[moteaux]

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.

[dsags]

Moteaux, thanks for the very informative post. Well done.

Dan

[moteaux]

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

[moteaux]

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

[moteaux]

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.

[GS66]

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.

[Loren At 65GS]

Moteaux, thanks for the very informative post. Well done.

Dan

X2

  Loren

[cwmcobra]

X3!

Chuck

[moteaux]

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.

[elagache]

Thank you moteaux for providing such a nice explanation of your transmission installation!

Cheers, Edouard 

[GS66]

Yes, this is great information! Thank you!