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Diff ratio - compare revs 3:15 v 3:54 |
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jpnjim
AMC Addicted Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752 |
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Yeah it's a tiny DOHC 1.6L, but its actually an oversquare engine, with a stroke longer than the bore is wide (3.1" bore 3.2" stroke), but will still run like the engine in your leaf blower, wide open without a care in the world. It makes plenty of power at 2500 to push the little jelly bean along at 80+, the larger Ford Escape with the same engine turns less RPM on the highway than that, but the Escape has an automatic transmission to eliminate the driver lugging the engine. With a 6 speed manual the same engine in an 800 lb lighter Fiesta is geared much lower, only explanation that makes sense to me is concern that operator error of lugging it along in high gear under 2000 rpm will lead to bad things fast.
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71 P-code 4spd Javelin/AMX
some Jeeps and some Fords |
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Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1815 |
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Even those they are driving down the cruise rpm. My wife's Jeep has the 9 speed, and it cruises at 1800 rpm going 75 mph, in 8th gear. And that's with the 3.52 towing package effective axle ratio. It won't go into high gear unless you are on a downhill above 80 mph.
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jpnjim
AMC Addicted Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752 |
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I honestly hate the way new automatic transmissions drop 3-4 gears when you touch the gas pedal, I completely understand all the logic behind them working that way, but I don't always want to see 6000 RPM to pass a minivan. Breaking in the engine on the Escape when it was brand new made me crazy Zero miles on it and its flirting with 5000 RPM's every time you look at the gas pedal sideways. I'll stick to manual transmissions as long as I have two feet and they keep making them.
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71 P-code 4spd Javelin/AMX
some Jeeps and some Fords |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4741 |
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I agree. I hate modern engines and drivetrains. When I blew up the engine in my Pontiac out in Kansas on vacation I rented a 2017 GMC Savanna van and a 2-wheel dolly to tow it back home to Arizona. It had a 4.8L Vortec with a 6-speed automatic. It wanted to cruise 65 MPH in 6th gear (1800 RPM), which was fine....downhill. It wanted 5th (2400 RPM) on a level and 4th (3200 RPM) for any little hill. A big hill it wanted 3rd (4200 RPM). It was constantly hunting gears. You'd think having tow/haul mode on would stop that, but tow/haul made it far worse. I found the manual shift feature that gave me a digital tachometer. I locked it into 4th gear and I left it there most of the time except when a big hill came up, then I downshifted to 3rd. It pulled the rocky mountains in 3rd. I drove it 1100 miles like that. Like most modern engines, it had no torque at low RPM. All the power was up at the high end. It was worthless below 3000 RPM but pulled like Babe the Blue Ox above 4000. That little 4.8L really surprised me at high RPM. What a screamer. Very smooth and quiet at high RPM. But I prefer big blocks and Diesels. Gear it down and chug along at 2500 RPM...meaning a 1965 Imperial Crown with a 413. I love how those drive on the highway. Just lock the cruise control in at 95 and relax behind the wheel to my Frank Sinatra collection.
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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Craigie
AMC Nut Joined: Sep/06/2011 Location: Bris, Australia Status: Offline Points: 369 |
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Thanks guys, I am really enjoying the read and finding your knowledge very helpful.
Yes AMXDREAMER, as Sonic Silver has mentioned, running 14 inch rims with 235 x 60 on the front and 245 x 60 x 14's on the rear. I am getting the front tyres rubbing the fender now, but maybe an option to run something slightly larger on the rear in conjunction with some gearing change to the diff ? Maybe I should look around for a pair of 15 inch rally rims to put on the rear for the extra long Highway runs ? I have just spent plenty rebuilding motor and tranny, so won't be looking to swap the tranny out anytime soon. |
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Craigie.........
1968 Dodge Charger "Bullitt" tribute 1971 SC/360 Hornet 1973 "Levi" Gremlin |
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Craigie
AMC Nut Joined: Sep/06/2011 Location: Bris, Australia Status: Offline Points: 369 |
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do have some space in the rear for a bigger rim or tyre
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Craigie.........
1968 Dodge Charger "Bullitt" tribute 1971 SC/360 Hornet 1973 "Levi" Gremlin |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19611 |
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I use the tire size and gear calculators at www.4l0.com... only because it's so easy to remember! Ignore the "LT" in front of tire size. Stands for "light truck", and the only difference between a light truck and car tire is the tread design (and maybe more plies/tougher), sizes are the same. Use "1" for the transfer case ratio (1:1). Get the diameter of the tire size you want, then plug that into the gear calc. Leave whatever you want it to calculate blank. It will calculate needed tire diameter, then you can find a tire size that's close. Hard to find some diameters, and there can be a +/- 0.25" between manufacturers (only 25-50 rpm). If you want a 3.08 axle Jeep XJs used 3.08 with the 4.0L/5 speed combos. It might be easy enough to find, and the D35 is tough enough for a mid range 360 on street tires. It will be fine for an occasional trip down the strip on heater slicks, but regular drag racing would accelerate wear. Don't think you'd break anything without warning, it should start making warning noises first. 5-6 passes with cheater slicks 2-3 times a year shouldn't faze it. That many every month will likely wear it out in a year or two. The XJ axle will fit a Hornet, but you'll need to cut the shock mounts off and weld in new spring saddles. It's a bit wider, but fits perfect with the deep Jeep wheels or deeper aftermarket wheels. Save on the rear axle, but make up for it in wheels. You can get new 3.08 gears, but not 3.15 that I could find. Goes from 3.08 to 3.31.
Edited by farna - Nov/07/2018 at 6:10am |
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Frank Swygert
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Online Points: 5787 |
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You would probably need to have 14" rally wheels re-rimmed to 15", the chances of finding some in Australia is next to zero and you might have noticed the command pretty high prices stateside.
Taller tires will help with the gearing, maybe even if you just bolt them on for longer road trips. Given that is is a genuine SC360, I'd imagine you probably want to keep the drive line original. Here are some 15 x 8 rally wheels I whipped up earlier: PS: If you can get something like a 29" tall tire under there (it's 25.6" at the moment), say 255/70/15, then that would have a similar effect to going from 3.54 to 3.15 with the gears.
Edited by WesternRed - Nov/07/2018 at 6:17am |
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I've finally given up drinking for good...........now I only drink for evil.
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Craigie
AMC Nut Joined: Sep/06/2011 Location: Bris, Australia Status: Offline Points: 369 |
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lol............... you teasing me with the pic of the Rims
Yes, a couple of those will be on my future shopping list. Even though it's not the original motor and Tranny, they are period correct for the car so really can't see me changing them out at any stage. The 3:15 or 3:08 diff gear will also be part of the shopping list after I try the rear tyre/rim option ............. I suspect the combination would be the ducks nuts !! |
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Craigie.........
1968 Dodge Charger "Bullitt" tribute 1971 SC/360 Hornet 1973 "Levi" Gremlin |
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Online Points: 5787 |
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You might be able to throw a pair of Jeep XJ wheels on the back just to see how it runs with taller tires, they have the same stud pattern.
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I've finally given up drinking for good...........now I only drink for evil.
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