Vintage Mustang Forums banner

41 - 54 of 54 Posts

·
Registered
Joined
·
65 Posts
Discussion Starter #42
Let me explain this with real numbers.

Your current combination of 27" tire, 2.99 first 3 speed & 2.75 rear gears gives you a 8.223: 1 starting ratio. You complain it's tough to get off the line and your RPM at 60 is @ 2000

If you use a wide ratio toploader, the starting ratio with the 3.50 gears is 9.73, with 3.25 is 9.04. These are much closer what you want.

If you use the close ratio unit with the 2.32 first, to maintain your current starting ratio, you need a 3.50 gear at a minimum. That gives you no off the line improvement, other than better ratios for street driving once you are moving. This also moves your 60mph RPM up to @ 2600. Again, no improvement to your complaint. To improve your off the line performance, you'd need to get into a 3.70 (8.58: 1, 2700 @ 60) or 3.89 (9.03:1, 2900 @ 60).

If you want to see what 3.89 gears are like, drive around in second gear with your 3 speed. Not sure how a 351-2V is going to like that RPM.

I've run close ratio, wide ratio, every gear from 2.75 up through 4.11. For an all around fun setup, I'd choose a 3.50 rear with a wide ratio trans.


71-73 351 4 speed cars came with either 3.25 or 3.50 gears from the factory for a good reason.
I do understand the dilemma, and I greatly appreciate all the input, My first gear is not really all that much a problem right now, its just it would be nice if it was lower, If I kept that to feel close to the same and have closer easier gear selection after that I would be happy with that. So it seems the big question is could I live with the little time I might spend on the highway with 3.70 rear,, and live with that. I know this is a tough subject in some ways so again I do appreciate the help. I guess I am going to depart with my tail between my legs and give it all thought.
 

·
Registered
Joined
·
1,555 Posts
The problem I have with the WR T56 is the .5 OD. It's pretty useless for anything but flat land freeways, and you may find yourself downshifting one or two gears just to pass someone.
I have a T56 in my 04 cobra. 6th gear IS just a cruising gear. You really have to downshift to 5th or 4th to pass with any sort of ambition.

Well I paid 650 for it, It came with a 302 bell housing, And it looks perfect inside and feels smooth , So many cars where built with this trans with lower rear ratios that it makes me wonder if I can make it work. I don't need to live in a perfect world, I really don't drive out on the highway any distance , The car is just a toy, I hate to go through the selling and re looking process.
You still got a good deal on that Tranny.. I would probably snap that up, for a spare if I saw that deal nearby.

If you are not planning much highway driving, or road trips.. You can drop in some 3.80 hears and probably do just fine. You might could get the 3.50 hears to work, but I would recomment a couple things. Make 100% sure you have a perfect clean and fresh flywheel. Also, choose a clutch/pressure plate that will give you the smoothest engagement possible. That will make a big difference in how comfortable this feels to drive. ANY sort of clutch 'chatter' is going to be amplified when you start off the line with that 2.32 first gear and a 3.50 rear gear.

(and FWIW: 3.89 are typically 9" gears. I think for an 8" you can get 3.80s).. Not a huge deal, but the available, common gears are different for some reason.. just be aware..
 

·
Registered
Joined
·
1,555 Posts
That’s just multiplication of your first gear ratio and your rear/axle ratio.

you can find a chart that shows all the tranny first gear# on ’David Kee Toploaders’

there are also calculators to help determine what speedometer gear you need to use that takes into account your tire diameter, But that more than what you asked for.
 

·
Registered
Joined
·
65 Posts
Discussion Starter #46
That’s just multiplication of your first gear ratio and your rear/axle ratio.

you can find a chart that shows all the tranny first gear# on ’David Kee Toploaders’

there are also calculators to help determine what speedometer gear you need to use that takes into account your tire diameter, But that more than what you asked for.
Got It Thanks
 

·
Registered
Joined
·
3,623 Posts
The problem I have with the WR T56 is the .5 OD. It's pretty useless for anything but flat land freeways, and you may find yourself downshifting one or two gears just to pass someone.
Yeah, but actually, the .5 OD is one of the things I like about it. According to the Ford engineers that I talked with, the Coyote will cruise happily at almost idle speeds, 1,400 is sweet spot for economy with a little power. With a 3.5 rear gear, calculations show 1,750 RPMs at 75 MPH. That should give decent economy while retaining some oomph...and if the need to downshifts arrises, part of the fun of having the clutch.
 

·
Registered
Joined
·
9,708 Posts
Could someone lead me to the tool / Web sight that helps to determine the Final start ratios based on all factors? If I am saying that right.
As noted, final drive ratio x first gear ratio

This RPM calculator is quick and simple. It will also factor the tire diameter. 71-73 factory tires were -on average- 26" tall.

 

·
Registered
Joined
·
65 Posts
Discussion Starter #49
Ok, So I thought I would just report back in after days of thought. First and most important is to thank everyone for there input. Its awesome to have a place to help figure something like this out from others experience. And the web sights that have been shared really helped put things into place as far as understanding.
So for starters, I probably used a misleading choice of words describing the cars current shifting , The thing is this car was off the road for 40+ years and all froze up and I had to take it down to the short block and clean and re assemble and replace alot. I have only had it for around a year and its come leaps and bounds over what it was. The reason I bring that up is most of the driving so far has been test drives up and down the street and up until recently while figuring things out , the car wasn't running great. So anyway the car has no tach, So I installed one and took the car out to see what 2500-3000 RPM feels like in the seat of the pants. I actually did 50 or so MPH in 2nd gear nearing around 2700 RPM with my 3 spd. I also just drove it more than usual and would have to say that my 1st gear is really not that bad once I get use to it. And also the highway speed is fine. I just wish there wasn't such a step between gears.

So how do I feel about doing 50 MPH at 2700 RPM ? and how do I feel about 3000 RPM ? Well I'm kind of a neurotic mechanical minded guy so I'm really not sure yet. But at 3000 I feel like I am beating up on it. But that could also be that in second while maintaining speed my 3 spd has a pretty pronounced whine. I am going to take it out today and drive it more.
Pretty much the conclusion is that I see exactly why I am being told to get a wide ratio. And so if I choose to use the close, with a 3.50 rear I will do 50-55 MPH at 2500-3000 RPM and my 1st gear will be a tweek higher than what I have, If I go with a 3.70 rear it will slow me to 49-53 or so MPH at those engine speeds and give me a slightly lower 1st gear. If I find a wide ratio I can use that 1st gear ratio to up to higher highway speed with a 3.25 rear or maybe 3.00.

I am tempted to try this trans with the 3.70 so far because I have it already and I do not drive much and it would probably be a blast 95% of the time based on where and when I drive. This is just a toy not something I have to depend on.

Some of the interesting thoughts I've been having , I own a 1971 camaro z-28 with 3.73 rear, 400 automatic. and if /when I go on the highway it runs around 3200 RPM at 55-60 and I really don't feel like its a problem. But then a small block chevy might be more comfortable than a 351C , I really don't know when a healthy 351C gets unhappy. So I go by what I feel when I drive it.
Anyway,, again thanks to all. I just wanted to share my thoughts so far. I am going to take the car out today and drive it more.

Oh and if I cant do over 65 MPH I wont have to worry about that slight shake in the front end for while that starts around that speed. Lol
 

·
Registered
Joined
·
3,033 Posts
1BD, My recommendation is to get a wider ratio trans, like the Jeep gearsets or maybe the 'imposter' TL. I have a friend with the 3.91 gears, and 27 inch tall rear tires, in a 69, and it is really a 'point & shoot' car only. For drag racing its great, but for highway, or even just cruising around, its too much. The engine will live just fine @ 3K, all day, everyday. But you may not want to listen to it or pay for all of the fuel. LSG
 

·
Registered
Joined
·
1,555 Posts
1BD, My recommendation is to get a wider ratio trans, like the Jeep gearsets or maybe the 'imposter' TL. I have a friend with the 3.91 gears, and 27 inch tall rear tires, in a 69, and it is really a 'point & shoot' car only. For drag racing its great, but for highway, or even just cruising around, its too much. The engine will live just fine @ 3K, all day, everyday. But you may not want to listen to it or pay for all of the fuel. LSG
I dont really do much highway driving with my CR toploader, but wish it was a little better off the line considering the 3.80 hearing I have. I have been seriously thinking about ordering a new All aluminum wide ratio unit from David Kee. Probably 75lbs lighter
 

·
Registered
Joined
·
65 Posts
Discussion Starter #52
So as this thread fades off into the sunset I am bringing it back to ask another stupid question, With understanding all the advice I have gotten here, and understanding that there really is no right way to do something wrong with this gearing thing. I started wondering if I could somehow change the gearing in the C/R I have and I see it is a doable thing. Although I am sure there is a good explanation for it , I just wonder with a kit that is sold to convert from close to wide ratio, why the number of teeth are the same on the first gear? How does that work?
 

·
Registered
Joined
·
3,033 Posts
1BD, the ratio will be affected by all of the gears in use when a certain speed is engaged. In first, you have a 'head set', with a gear on the input shaft, and a gear on the front of the countershaft. Then, there is another gear for 1st speed on the end of the countershaft, and another that matches it on the output shaft of the trans. you need to know the teeth on all four of these positions to figure out the gear ratio. LSG
 

·
Registered
Joined
·
65 Posts
Discussion Starter #54
Thank You very much, That explains it. I could not wrap my head around why the first gear would have the same amount of teeth in both wide and close ratio, but I understand it is the size of the fourth gear and others on the input shaft that will change the speed by ratio of the cluster gears. THANK YOU.
 
41 - 54 of 54 Posts
Top