Anybody here swap out an automatic transmission for a manual on a GT500?
shouldnt be too dificult.
If you consider doing it and are looking for parts, I have a restored 69 clutch pedal assy , rebuilt big shaft toploader , and possilby a 428 flywheel.
drop me a message if youd like to talk
If you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
Quote from: brandosaac on August 07, 2026, 07:12:28 PMshouldnt be too dificult.
If you consider doing it and are looking for parts, I have a restored 69 clutch pedal assy , rebuilt big shaft toploader , and possilby a 428 flywheel.
drop me a message if youd like to talk
Thank you!
Quote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
I'm well past a "judging" car. Never really wanted one to begin with, so I'm more interested in making my GT550 what i want it to be regardless of anything else. Thanks for the input!
Besides the pedal assembly ,clutch rod and equalizer bar there are other things that might surprise you when you add them up. The big input big output 4 speed trans will be pricey when you find one that is ready to go at 2000.00-2600.00. The 390 trans is much cheaper but will not take the abuse that the other will. There is a specific big block bellhousing that is designed for the 11.5 clutch and pressure plate needed is about 700.00-900.00. The earlier 66 390 style would be cheaper that is designed for a smaller clutch and pressure plate. There is a different clutch fork for the 428 vs.390 .The driveshaft is longer on a manual compared to an automatic so you will not be able to make that work. This plus all of the other supplemental hardware brackets etc. adds up to a substantial chunk of change. Also I believe I am being conservative with my used part numbers.
Quote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
Quote from: gt350shelb on August 08, 2026, 07:38:58 PMQuote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
True - but the next buyer may reduce his offer if he needs to pay a shop and extra hour to repair the hole for concours. I realize a couple hundred isn't a big hit but it all adds up when someone is looking for a car to restore vs a driver.
Since you are not looking for originality consider this - https://www.summitracing.com/parts/awr-cofo-m1ex?seid=srese1&gad_source=1&gad_campaignid=1012069904&gclid=Cj0KCQjwp9vTBhCWARIsANaUrjv8jzz15PRjmgU9gGbqE_YXFyqpHbtWWvCyoVS-d9xKrPm-0qObhGYaAh17EALw_wcB
One thing that Bob missed in his parts list is the rearend. Automatics generally run a taller gear. If you want to retain the performance you'll need to go to a numerically higher gear - Early cars ran a 3.89 with the 4 speed and a 3.50 with the auto. The 5 speed will allow you to run even a 4.11 and still have acceptable revs while cruising down the road.
Quote from: 98SVT - was 06GT on August 08, 2026, 08:06:32 PMQuote from: gt350shelb on August 08, 2026, 07:38:58 PMQuote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
True - but the next buyer may reduce his offer if he needs to pay a shop and extra hour to repair the hole for concours. I realize a couple hundred isn't a big hit but it all adds up when someone is looking for a car to restore vs a driver.
Since you are not looking for originality consider this - https://www.summitracing.com/parts/awr-cofo-m1ex?seid=srese1&gad_source=1&gad_campaignid=1012069904&gclid=Cj0KCQjwp9vTBhCWARIsANaUrjv8jzz15PRjmgU9gGbqE_YXFyqpHbtWWvCyoVS-d9xKrPm-0qObhGYaAh17EALw_wcB
One thing that Bob missed in his parts list is the rearend. Automatics generally run a taller gear. If you want to retain the performance you'll need to go to a numerically higher gear - Early cars ran a 3.89 with the 4 speed and a 3.50 with the auto. The 5 speed will allow you to run even a 4.11 and still have acceptable revs while cruising down the road.
Last fall I did a swap for a customer with a 67 S code Cougar with a Tremec from Hamlin Motorsport. Supposed to be a complete kit and bolt in. It still needed a few things and the crossmember needed some work to fit, but overall it went together well. Had to cut the shifter hole in the floor a little. A different handle would fit without trimming.
But what a different experience running it through the gears and 5th made it fantastic for cruising at 75-80. Nothing that couldn't be put back to original if you decided to do so. I'd just recommend keeping all the parts removed for the future.
I was very close to putting a Tremec TKX 5 speed into my '69 GT350 convertible with an FMX this year. I am 6'4" and decided to try sitting in an identical car that was converted to a 5 speed. I couldn't shift comfortably without my knee hitting the door panel, steering column and/or turn signal switch. The clutch pedal sits pretty high, and I know it can be adjusted with some work. Also the seat can be moved back. In the end, I didn't want to fight physics. Besides, my car is faster with the automatic and easier to drive in traffic.
As mentioned above pay close attention to gear ratios . The common swap back in the day was 5 speed from 5.0 mustang. If you use one with these ratios you need to go down in rear gear 3.00 3.55 max. If you run 3.89 1st and 2nd gear are pretty much useless . (5.0 mustangs came with 3.08 rears in the 80 s and 90s )
Quote from: Bob Gaines on August 08, 2026, 06:45:59 PMBesides the pedal assembly ,clutch rod and equalizer bar there are other things that might surprise you when you add them up. The big input big output 4 speed trans will be pricey when you find one that is ready to go at 2000.00-2600.00. The 390 trans is much cheaper but will not take the abuse that the other will. There is a specific big block bellhousing that is designed for the 11.5 clutch and pressure plate needed is about 700.00-900.00. The earlier 66 390 style would be cheaper that is designed for a smaller clutch and pressure plate. There is a different clutch fork for the 428 vs.390 .The driveshaft is longer on a manual compared to an automatic so you will not be able to make that work. This plus all of the other supplemental hardware brackets etc. adds up to a substantial chunk of change. Also I believe I am being conservative with my used part numbers.
It's ALWAYS more than we think it's going to be! It's an interesting idea, just entertaining it and knew this would be the place to ask about it. Thank you!
Quote from: gt350shelb on August 08, 2026, 07:38:58 PMQuote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
LOL!!!
Quote from: 98SVT - was 06GT on August 08, 2026, 08:06:32 PMQuote from: gt350shelb on August 08, 2026, 07:38:58 PMQuote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
True - but the next buyer may reduce his offer if he needs to pay a shop and extra hour to repair the hole for concours. I realize a couple hundred isn't a big hit but it all adds up when someone is looking for a car to restore vs a driver.
Since you are not looking for originality consider this - https://www.summitracing.com/parts/awr-cofo-m1ex?seid=srese1&gad_source=1&gad_campaignid=1012069904&gclid=Cj0KCQjwp9vTBhCWARIsANaUrjv8jzz15PRjmgU9gGbqE_YXFyqpHbtWWvCyoVS-d9xKrPm-0qObhGYaAh17EALw_wcB
One thing that Bob missed in his parts list is the rearend. Automatics generally run a taller gear. If you want to retain the performance you'll need to go to a numerically higher gear - Early cars ran a 3.89 with the 4 speed and a 3.50 with the auto. The 5 speed will allow you to run even a 4.11 and still have acceptable revs while cruising down the road.
Saw that, but hadn't thought about the rear end. Good input, thanks...
Quote from: jimhyc on August 08, 2026, 09:16:46 PMQuote from: 98SVT - was 06GT on August 08, 2026, 08:06:32 PMQuote from: gt350shelb on August 08, 2026, 07:38:58 PMQuote from: 98SVT - was 06GT on August 07, 2026, 09:03:55 PMIf you decide to do it you will need to drill the hole out in the firewall where the clutch shaft goes. An expensive fix if you ever decide to restore it for judging.
i see this as a next owner problem
True - but the next buyer may reduce his offer if he needs to pay a shop and extra hour to repair the hole for concours. I realize a couple hundred isn't a big hit but it all adds up when someone is looking for a car to restore vs a driver.
Since you are not looking for originality consider this - https://www.summitracing.com/parts/awr-cofo-m1ex?seid=srese1&gad_source=1&gad_campaignid=1012069904&gclid=Cj0KCQjwp9vTBhCWARIsANaUrjv8jzz15PRjmgU9gGbqE_YXFyqpHbtWWvCyoVS-d9xKrPm-0qObhGYaAh17EALw_wcB
One thing that Bob missed in his parts list is the rearend. Automatics generally run a taller gear. If you want to retain the performance you'll need to go to a numerically higher gear - Early cars ran a 3.89 with the 4 speed and a 3.50 with the auto. The 5 speed will allow you to run even a 4.11 and still have acceptable revs while cruising down the road.
Last fall I did a swap for a customer with a 67 S code Cougar with a Tremec from Hamlin Motorsport. Supposed to be a complete kit and bolt in. It still needed a few things and the crossmember needed some work to fit, but overall it went together well. Had to cut the shifter hole in the floor a little. A different handle would fit without trimming.
But what a different experience running it through the gears and 5th made it fantastic for cruising at 75-80. Nothing that couldn't be put back to original if you decided to do so. I'd just recommend keeping all the parts removed for the future.
Excellent! I was hoping to hear from someone who had done it. Thank you!!!