Varilux":37cwbmlz said:
I've often heard the phrase "don't fear the gear," but now I understand it...
It goes both ways for cruising rpm, verses axle ratio, but gearing down for an I6 axle ratio to a numerically lower ratio is just fine.The stock non Fox 3.3 Mustang gears were 3.20 manual, 2.88 auto, so 3.55 and 3.40 is certainly great with any T5 5speed. If it was auto, you just lost at least 16 hp flywheel around town, and your always running a taller than manual axle ratio that's over 10 % taller geared if the car was born an auto. That's why running a manual makes a formerly auto 200 feel like its grown about 50 cubic inches, to behave more like a 250, 255 or 260 engine torque wise. Its that significant vote in favour of having a manual T5 3.3 with your gearing.You've cracked the code! A 5 speed 302 Mustang feels like a 370 cube engine compared to an AOD 5.0. Same dynamic applies, more around town hp loss, and a loss of acceleration because almost always Ford gears the autos up more than 10% higher.
65-coupe":37cwbmlz said:
I have a 4cyl T5 with in mine with a 340 rear gear. It is a blast to drive and gets going quick. I wish the OD was .69 not the .79 that it has. I am running about 2700 at 75MPH. It would be nice to be about 2000-2200. But the price was right for the 4cyl. T5 is the best mod you can do to it.
When gearing for open road, you need more overdrive, and the V8 T5 has a huge over driven 5th.
I've done the research, and at an overall axle ratio of 2.35:1, that 0.69 wouldn't be too high. The Car and Driver 4.2 Capri of 1981 had 0.67:1 top with 3.45 gears, and it was wonderful with just a modified 160 hp 4-bbl. A 3.3 with a CI alumimum head won't have a problem eclipsing a modified 4.2 between 2200 and 3000 rpm. A good little 3.3 is a better engine than a 4.2...but I'm showing you
why a little 3.3 can take much wider gearing. The 4 speed auto V8 4.2 verses T5 3.3 is a valid gearing comparison, as a worked I6 has its measure, and is close to the 5.0 2-bbl Fox SROD's which had a 2.13:1 overall top gear. The tallest Fox overall top was
generally 2.26, which is a figure no overdrive should go over. Later 5.0's with 2.73's did have a 1.83:1 top, but a 225 hp 5.0 is a very tough act to match, and you wouldn't spoil anything by adding those ratios.
That 2.26:1 maximum means the limits of gearing are
With a T5 5.0 5th of 0.72 or 0.69, that's 3.13 to 3.27 axle gears, so 3.25's will do, but feel free to go 3.4 or 3.55
With a T5 4 cyl 5th 0.79, that's 2.86 axle gears, so a 2.88 will do, but feel free to go 3.0 or 3.20
Evidence to support is
http://www.ascmclarencoupe.com/Literatu ... 1_2_04.jpg
Problem is the T5 4 cyl is a a close ratio and wide ratio mixture, its wide ratio intermediates, with close ratio top
The T5 5.0 is close ratio intermediates and wide ratio top.
Its not easy to mix and match the ratios because of the cost of non standard parts
Where it might be a problem is "gaping" it between speeds in give and take roads, but unless your in Idaho or Southern California, maybe you don't have roads like that. The info I have is that its better to find a 0.80/0.79/078 5th, and 3.00:1 with a wide ratio intermediates might be best in that instance. Especially with the excellent CI head, which makes a huge amount of torque over such a a wide rpm range with most Clay Smith cams. Close ratio gearboxes are used when you have a very cammy engine, without low end torque.
The issue is that in a car that isn't as slick as a modern car, its better to keep the upper 3 ratios closer, and gear up the diff. Historically, 5 speed gear ratio selection started to be questioned when the aero cars with 30 to 40 less drag than there previous models hit town in the early 80's. Although its an itty bitty 2.2 5 cylinder, in the 1982 Audi 5000 era, slicker aero figures allowed the German versions to run very wide ratio 5speed gearboxes in a 2800 pound car. Car that couldn't do 118 mph with 0.42 cd could do 128mph 0.32 and still the same 134 hp, a 31% drop in aerodynamic drag. US cars needed a turbo to get not turbo Euro performance, but In the lighter 2500 pound Audi Fox/80/5+5, the2.2 5e with wide ratio 5 speeds were great, but as the pounds were piled on in the bigger car, the wide ratio selection was a real pain to chop and change with the 5000 in the 55 to 100 mph zone. In Australia, it was a problem with the stupid 62 or 68 mph speed limit, so the old close ratio gearbox was employed in the manual versions. The gearing is owners choice, and as long as 3.3 I6 Ford owners are using there own smarts, its doubtful you'll ever be disappointed at the advice here.
The 'Aussie experiment' with Audi 5000 and small Fox 80 5+5 gearing gearing also showed true with the 3.3 to 3.5 liter sedans in the 121 to 142 hp and 173 to 177 lb-ft range like the X-flow 2-bbl I6 Aussie Falcon XE/XF and twin carb or EFI V8 Rover 3500, They used the 3.23 and 3.08 ratios with small 0.79-0.77 overdrives and short, close ratios like 3.24 firsts was perfect with tall tired cars. They did 111 mph to about 117 mph, better than the early box bodied non aero Audi 5000 Turbo. That's how gearing works. The Falcon was a really boxy and un aero car in 1982, yet it did 2200 rpm at 62 mph, and 32.6 US mpg on the economy loop at 62 mph. The 5 speed and 3.23 diff made the car a delight.
I guess the US situation is different, but Ford Oz started to go to shorter, 1st: 3.50:1, 2nd: 2.14:1, 3rd: 1.39:1 intermediates, with taller axle ratios as the cars cd (drag factors) dropped 39% from 0.50 to 0.36, but they kept the over drive ratio well down to a 4 cyl T5 level.
Everything is interrelated to drag at freeway speeds, and Aussie roads are rougher, not often concrete, and modern Ford passenger cars after 1982 are able to take wide ratios, so the donated V8 might not be the best for everyone.