gears
Thread Starter
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Joined: Jul 2012
Posts: 64
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From: Bossier City Louisiana
gears
I have factory 411s with m21. They are too low to drive any distance. I want to keep some of my lowend torque but at the same time I want to be able to drive it to shows out of state. I'm thinking 336 or 355. Give me your input on this. Thanks, Jackie
Drifting
Joined: Mar 2011
Posts: 1,402
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From: Iowa
Deuce,
I have been this similar path and after wasting my money doing a gear change in which I still wasn't happy, I later figured out the 5 speed option to be the best.
For example, had both a 4:11 and 3:73 with wide ratio muncie and neither were really practical for extended highway use (in my opinion). I then tried 3:55s and although a little better in terms of lower rpms, the car started to feel "heavy" and I didn't like it...again, I prefer the feel of the lower gears.
Your 383 should have enough low end torque to make a 3:36-like gear choice ok, BUT, after having been down this road as well, I found that swapping to a 5-speed was the best way to address the issue.
I have done this on 2 separate cars...both with strong 383s, I added a TKO600 in each application and one had 4:11s and it was great.
My current 67 has a 383, TKO600 with 3:73s and it is great as well.
Again, just a different thought.
Frank
I have been this similar path and after wasting my money doing a gear change in which I still wasn't happy, I later figured out the 5 speed option to be the best.
For example, had both a 4:11 and 3:73 with wide ratio muncie and neither were really practical for extended highway use (in my opinion). I then tried 3:55s and although a little better in terms of lower rpms, the car started to feel "heavy" and I didn't like it...again, I prefer the feel of the lower gears.
Your 383 should have enough low end torque to make a 3:36-like gear choice ok, BUT, after having been down this road as well, I found that swapping to a 5-speed was the best way to address the issue.
I have done this on 2 separate cars...both with strong 383s, I added a TKO600 in each application and one had 4:11s and it was great.
My current 67 has a 383, TKO600 with 3:73s and it is great as well.
Again, just a different thought.
Frank
Thread Starter
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Joined: Jul 2012
Posts: 64
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From: Bossier City Louisiana
Thanks, Frank for the info. I have 535hp 383 w/ 506 tq so i should have torque for 336 or 355. I have been thiking about the tko 600. will keep the close ratio ut have a overdrive. Jackie
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Racer
Joined: Feb 2013
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From: Long Beach Ca
I have a numbers matching 66 M21 close ratio with an L79 327. I believe from what I have read here that the L79 came standard with the m21 and 370 gears. Someone over the years installed 336's. IMHO the close ratio combined with 336 rears is a bad combination. Highway driving is ok (3000 rpm's @ 65 mph) but the car is a bear to get moving. I'm with Frank on this one. A new OD trans either a Keisler SS700 or a tremec is in my future plans.
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O/D trans is the best option. If you're going to pay $$$ to swap the whole differential or gears...you're halfway to a new trans.
JIM
JIM
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Joined: Nov 2003
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From: Maryland
St. Jude Donor '05, '09, '15
535hp 383 w/ 506 tq TKO600 and a 4:11 rear? The overdrive would be OK for cruising but I would think 1st gear would be pretty useless except for smoking tires. Not that there is anything wrong with smoking tires 
but do you want to do it every time you pull away from a stop? I would think you would have no problem with 3:36 or even 3:08 with that engine and 4 spd trans.
Tom
but do you want to do it every time you pull away from a stop? I would think you would have no problem with 3:36 or even 3:08 with that engine and 4 spd trans.Tom
Last edited by Sky65; Jun 30, 2013 at 10:53 PM.
Racer
Joined: Jan 2010
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From: Albuquerque Resistance is not futile. It's voltage divided by current.
With that engine you will be just fine with 3.08.On the other hand, an OD trans, IMHO, is the hot setup these days.
I have one on order.
Cheers, GA
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You can get several trans ratio's these days.
JIM
JIM