1969_Mach1 333 Report post Posted August 24, 2020 I currently have a 3.89:1 rear axle gear in my 1969 Mach 1. Now that I am older I'd like something a little lower since the motor revs pretty high just cruising at 45 to 50 mph. Trans is a close ratio toploader 4-speed, motor is a 351W, original 14" wheels with tires that are 26" tall. I'm thinking either a 3.70:1 or a 3.50:1 rear axle gear. First gear in this trans is only 2.32:1 so I am not certain how well it will work with a 3.50:1 rear axle ratio. Anybody have experience with this type of trans and rear axle gear combination? Quote Share this post Link to post Share on other sites
dream car 12 Report post Posted August 24, 2020 I'm very happy with my 3:50 rear axle, close ratio toploader With 351W. Driving around neighborhood sometime I don't even use 4th gear. Going from 3:89 to 3:70 is not going to make a lot difference for a lot of works. That just my opinion. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted August 24, 2020 Thanks, I've been wondering how that combination would work. I've been tinkering with the gear ratio calculators and yeah, 3.89 to 3.70 is only about 130 rpm lower at 50 mph. Quote Share this post Link to post Share on other sites
RPM 1,190 Report post Posted August 24, 2020 I know a couple of owners who are happy with 3.25s and toploaders. Quote Share this post Link to post Share on other sites
ClubSport 29 Report post Posted August 24, 2020 Switched from 3.25 to 3.5 when swapped my 8" to a 9" and the 3.25 was more convenient with my WR Top Loader Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted August 24, 2020 I'm starting to think a 3.50:1 might be the best choice with a close ratio trans. 16 hours ago, dream car said: I'm very happy with my 3:50 rear axle, close ratio toploader With 351W. Driving around neighborhood sometime I don't even use 4th gear. Going from 3:89 to 3:70 is not going to make a lot difference for a lot of works. That just my opinion. Does your car feel lazy at all in first gear? First gear in a close ratio toploader isn't very low, it's only 2.32:1. Unlike the wide ratio at 2.78:1. Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted August 24, 2020 I ran the 3.5 rear end in my 70 Mach1 pushed by a stout 351Cj and close ratio toploader. No problems getting it to move off the line, In hind sight a 3.25 may have been better for freeway travels. Anything taller in rear would have made putting the power to the ground a challenge, Spinning is not winning but does make a cool smoke show. Quote Share this post Link to post Share on other sites
dream car 12 Report post Posted August 25, 2020 7 hours ago, 1969_Mach1 said: I'm starting to think a 3.50:1 might be the best choice with a close ratio trans. Does your car feel lazy at all in first gear? First gear in a close ratio toploader isn't very low, it's only 2.32:1. Unlike the wide ratio at 2.78:1. In my younger year , I would probably preferred the lowest gear possible. So I can smoke the tires , and ludicrous mode on take off. Now I don't even drive on the freeway fear of rock chips. My 3:50 don't feel lazy in first gear, its a factory standard ratio for the GT-350 4 speed. Unless you are still young at hart, that would be different situations. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted August 25, 2020 2 hours ago, dream car said: In my younger year , I would probably preferred the lowest gear possible. So I can smoke the tires , and ludicrous mode on take off. Now I don't even drive on the freeway fear of rock chips. My 3:50 don't feel lazy in first gear, its a factory standard ratio for the GT-350 4 speed. Unless you are still young at hart, that would be different situations. Young at heart, not as much anymore. Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted August 26, 2020 Can't be much help as my 3.50 gear and CR toploader are twisted by a 428CJ. Lots of fun and fuel. Dave R. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted August 26, 2020 16 hours ago, Dave R. said: Can't be much help as my 3.50 gear and CR toploader are twisted by a 428CJ. Lots of fun and fuel. Dave R. I only have a 351W, not nearly as much low end torque as your 428CJ. The only combination I've had experience with on a 351W Mustang and 3.50 rear axle gear also had an FMX auto trans. With the FMX's lower first gear ratio and torque convertor it was a good combination for street. Not lazy at all and could still cruise 55 mph. This was so long ago the highway speed limit was still 55. Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted August 26, 2020 Sounds like a fun combo also. Dave R. Quote Share this post Link to post Share on other sites
1969vert 55 Report post Posted August 28, 2020 I have a 3.0 with my top loader was a 2.79 8" before. just a cruiser.. Might be ISO a 2.79 gear for a 9" ..used.. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted August 28, 2020 On 8/26/2020 at 12:24 PM, Dave R. said: Sounds like a fun combo also. Dave R. That combo was in one of my older brothers 69 Mach 1 back in the early 1980's. He was one that would street race almost every weekend. On Saturday mornings I'd see all the rubber stuck to the rear quarter panels and rear inner fenders of the car. At first he'd clean off all the rubber before our father saw it. After a while he didn't care and left it on there. 1 RPM reacted to this Quote Share this post Link to post Share on other sites
stangs-R-me 120 Report post Posted September 1, 2020 My 351W has a Wide Ratio Top Loader, 3:50 Gears, and 225/60-15 (25.63" Dia.) tires. 2840 RPM @ 60 MPH or 3551 RPM @ 75 MPH in 4th. OK on 55 MPH back roads but screaming on the 70 MPH Interstate !! Doug Quote Share this post Link to post Share on other sites
RPM 1,190 Report post Posted September 1, 2020 14 hours ago, stangs-R-me said: My 351W has a Wide Ratio Top Loader, 3:50 Gears, and 225/60-15 (25.63" Dia.) tires. 2840 RPM @ 60 MPH or 3551 RPM @ 75 MPH in 4th. OK on 55 MPH back roads but screaming on the 70 MPH Interstate !! Doug Put some 27 inch or bigger tars on the back. 1 stangs-R-me reacted to this Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted September 8, 2020 Update, I've decided to go with a 3.70:1 ratio. After being use to the 3.89:1 gears it might feel lazy in 1st with a 3.50:1 gear. Now just to select from who. I've had good luck with Motive's performance series of gears and I've had good luck with buying some no-name brand stuff from shop near me that does rear axles and manual trans. Quote Share this post Link to post Share on other sites