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So I realize this is probably a topic thats been exhausted ,but I would like to ask opinion on what I am trying to accomplish. I have my 1971 mach1 thats an H code 351c 2v from factory with 3 spd top loader and 2:75 conventional rear. It is an adventure starting out in first playing the motor to the clutch getting started and then its never completely happy in a given gear until you are on the highway. I am not interested in the driving experience to the point of doing the T5 upgrade thing, I just want the car to feel less of a battle to drive.
So I have started by getting a 4spd trans, ( close ratio ) because I want to add another gear into the picture. I have not yet installed it, The first gear on the four speed is actually a higher gear than my 3 speed,,,Now I plan to purchase a rear differential with a gearing that will work nice. I was originally thinking 3:25 but am now wondering with the higher 1st out of the trans should I go 3:50. I will not be spending time driving long distances on the highway but don't want it to be over revving. and I want it to feel easier to start out and go through the gears without feeling like a dump truck. So I am calling for some members who might have enough experience playing around with different ratios or cars to help me figure out what would be best because I only want to do it once. By the way I have the factory hight wheels on the rear. Thanks very much for any input.
 

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I'd get rid of the close ratio toploader and get a wide ratio. I've run them on the street and while the gear spacing is nice, you need steep gears to make it work. With the 2.32 first of a C/R, you'll need to get into a minimum of a 3.50 rear to see the same multiplication as the 3.03 three speed, and you're not improving anything at that point. With a W/R, you can get a 3.25 and it'll give you a bit more off the line.
 

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Where do you drive, why do you drive, and how do you like to drive?
 

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I would even suggest the 3.50 gears is not very 'streetable' with a close ration toploader unless your motor is a real torque monster down low. I have that same Tranny in my car, and sort of have a Love-Hate relationship with it. I had to go with 3.80 gearing to make it even decent to drive, and it is just horrible to drive on the interstate. At this point. I am planning to either swap to a tremec 5-speed, or add a gear-vendors OD to my toploader. but for now, I just only drive it around town, so it doesn't matter that much
 

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3.50 gear will be good. Yes a wide ratio trans would be easier to get going from a dead stop, no question about that.
 

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I'd get rid of the close ratio toploader and get a wide ratio. I've run them on the street and while the gear spacing is nice, you need steep gears to make it work. With the 2.32 first of a C/R, you'll need to get into a minimum of a 3.50 rear to see the same multiplication as the 3.03 three speed, and you're not improving anything at that point. With a W/R, you can get a 3.25 and it'll give you a bit more off the line.
I agree. The close-ratio was typically seen on the 289HP and BOSS 302, and coupled with a 3.50:1 axle. For a street-driven car, a poor choice unless your driving is typically highway or wide-open rural roads.

I'm running a 289HP with a wide-ratio trans and 3.00:1 axle. Very driveable.

I have my 1971 mach1 thats an H code 351c 2v from factory with 3 spd top loader and 2:75 conventional rear. It is an adventure starting out in first playing the motor to the clutch getting started and then its never completely happy in a given gear until you are on the highway. I am not interested in the driving experience to the point of doing the T5 upgrade thing, I just want the car to feel less of a battle to drive.
My concern here is this statement. With a properly tuned 351C 2V and manual trans, my only problem would be smoking the tires.

Adventure? Pulling out from a stop should be dead easy. Does the clutch chatter? That's not the transmission's fault.

If you have no power and need to slip the clutch to start from a stop, your engine, not your axle and trans, is the problem.

Seriously, a 351C 2V should be able to smoke the tires at every pullout.

I suggest examining the carb, to be sure it's the correct one. Followed by a total tune-up, including carb adjustments, points, plugs, wires, cap, rotor, condenser. Send the distributor to Dan at the Mustang Barn. I guarantee it is currently WAY out of adjustment, which would kill performance even if everything else is perfect.
 

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I would think a 351-2v would make more tq down low then a 289hp or boss 302. But hey maybe it doesn't.
 

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3.50 gear will be good. Yes a wide ratio trans would be easier to get going from a dead stop, no question about that.

Didn't both the Shelby GT350 and the Boss302 come with a Close Ratio (2.32) Toploader mated to 3.80 - 3.79(?) gears?
 

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Discussion Starter #11
Where do you drive, why do you drive, and how do you like to drive?
I generally don't drive long trips, I generally drive for pleasure to local cruise ins and shows, and I am a pretty tame driver but like to feel like I have some muscle in the seat.
 

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OK, first, do to the engine what I suggested above. Might save you $1000+. Seriously. You should be having trouble keeping tires on the car, not having trouble pulling out of intersections. The 351C 2V is a tire-killer in town. Better low rpm torque than the 351C 4V.

An if you still want to make a change, go with a wide ratio 4-speed and 3.25:1 axle.
 

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Discussion Starter #13
I agree. The close-ratio was typically seen on the 289HP and BOSS 302, and coupled with a 3.50:1 axle. For a street-driven car, a poor choice unless your driving is typically highway or wide-open rural roads.

I'm running a 289HP with a wide-ratio trans and 3.00:1 axle. Very driveable.

My concern here is this statement. With a properly tuned 351C 2V and manual trans, my only problem would be smoking the tires.

Adventure? Pulling out from a stop should be dead easy. Does the clutch chatter? That's not the transmission's fault.

If you have no power and need to slip the clutch to start from a stop, your engine, not your axle and trans, is the problem.

Seriously, a 351C 2V should be able to smoke the tires at every pullout.

I suggest examining the carb, to be sure it's the correct one. Followed by a total tune-up, including carb adjustments, points, plugs, wires, cap, rotor, condenser. Send the distributor to Dan at the Mustang Barn. I guarantee it is currently WAY out of adjustment, which would kill performance even if everything else is perfect.
I did feel the relation to power on a proper tuned motor your talking about while I was first trying to get it running right, but there is no clutch chatter and its pretty powerful and runs well. maybe I painted a more bleak picture with the wording I used. All in all once the clutch is out I can raise the front suspension. It just feels like you have to think about the clutch release more than you should, Then driving down a back road I have the choice of whining 2nd or bogging third. If I wanted I probably could smoke the (tire) lol
 

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Discussion Starter #15
I agree. The close-ratio was typically seen on the 289HP and BOSS 302, and coupled with a 3.50:1 axle. For a street-driven car, a poor choice unless your driving is typically highway or wide-open rural roads.

I'm running a 289HP with a wide-ratio trans and 3.00:1 axle. Very driveable.

My concern here is this statement. With a properly tuned 351C 2V and manual trans, my only problem would be smoking the tires.

Adventure? Pulling out from a stop should be dead easy. Does the clutch chatter? That's not the transmission's fault.

If you have no power and need to slip the clutch to start from a stop, your engine, not your axle and trans, is the problem.

Seriously, a 351C 2V should be able to smoke the tires at every pullout.

I suggest examining the carb, to be sure it's the correct one. Followed by a total tune-up, including carb adjustments, points, plugs, wires, cap, rotor, condenser. Send the distributor to Dan at the Mustang Barn. I guarantee it is currently WAY out of adjustment, which would kill performance even if everything else is perfect.
Motor has rebuilt original carb and pretty much new everything including a petronix ignition, I tuned it with a vacuum gage , I dialed in the timing many times to make it start hot and run best and when your out on the road and you put it to the floor its like rocket.
 

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Maybe I should just get a 3:25 posi Diff over the 2:75 conv and keep the three speed and sell the Trans I bought.
ughhhh. not a "posi"... ;)

You are looking for an upgraded Trac-Loc differential. preferably one that has the four spider gears.

And if you mated that 3-speed tranny with 3.25 gears you would probably be very happy. I had that exact tranny/rear-gear combo in my first mustang behind a 302 2V for a few years. It ran really well. Ironlically, I put in a close ration toploader, and sold those gears :(
 

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Discussion Starter #18
ughhhh. not a "posi"... ;)

You are looking for an upgraded Trac-Loc differential. preferably one that has the four spider gears.

And if you mated that 3-speed tranny with 3.25 gears you would probably be very happy. I had that exact tranny/rear-gear combo in my first mustang behind a 302 2V for a few years. It ran really well. Ironlically, I put in a close ration toploader, and sold those gears :(
My plan was to buy a new differential from Speedway motors
 

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Didn't both the Shelby GT350 and the Boss302 come with a Close Ratio (2.32) Toploader mated to 3.80 - 3.79(?) gears?
I think the 65-66 GT350's typically came with 3.89 gears. The Boss saw 3.50 as standard. 3.91 and 4.30 were options.
 
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