I told my buddy that has a stock 1990 mustang gt who is looking into gears and wanted to know how much 4.10's would knock off of his ET, i told him around
3/10's of a second... Is this about righ,t or would it be a bit more/less?
Probably a little bit less. Here's the rub. With 4.10's his shift points need to be around
6,800 or so. Stock is limited to 6,250. So the potential is there to be a lot quicker with the 4.10's, the stock computer will limit his top speed/rpm at the top end. So by the time he hit the 1380-1390 ft mark (or so), he's maxed out and not accelerating. 3.73 is a better choice for a stock car. That keeps the shift points to a more reasonable 6,000 rpm's, and still have some power at the top end.
Ummm... this doesn't make sense. Shift points at 6800 for a stock
5.0? I think even 6000 seems high for a stocker. How can you possibly advise someone on shift points when he hasn't even told us what tranny his friend uses? Oh yeah, a quarter mile is only 1320 feet so your comment regarding 1380 - 1390 is kind of wacky as well.So Bev... give us a little more info on your friend's current setup (tranny, current rear gear, other mods) and maybe then you can glean a little useful info out of us. Basically the 4.10's are definitely going to help his acceleration. How much depends on what's in front of it and how his driving skills are. When I went from 2.73 to 3.73 in my 5-spd. 4.6 car I dropped nearly half a second off my 1/4 times.
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1998 GT Coupe 5-spd. Bright Atlantic Blue K&N FIPK, Tri-Ax, 3.73's, FRPP Coated Shorties, SpeedCal, P&P 2K Heads, 2K Intake, Bassani X-Pipe and Cat-Back, Subframe Connectors, JMS Chip, Eagle Alloy Wheels
Damn, thats more than i thought.....tom
Alot of people have said its about 1/10 for ever gear step you went up.
2.73, 3.08, 3.27?, 3.55, 3.73, 3.90?, 4.10......
Well, he said the car was stock, so that should be a T5. Factory red line is 6,250, so a reasonable shift point is 6,000.
Oh yeah, a quarter mile is only 1320
Duh. Where was I when the math grades were passed out? The point is, he'll run out of rpm's before he hits the end of the track. The 4.6L engines are capable of a much higher redline beacuse of the OHC. 6,800-7,200 rpm's is reasonable for them. But the 5.0's are pretty much limited by their hydraulic valve train.
It could be an AOD. He didn't say if it was a manual or automatic. 6000 is over what a stock 5.0 should be shifted at. It isn't making power at that point.
Using the calculator at
Driveability will be effected though. With that 4.10 rear and a 3.35 1st gear in the trans (assuming a T5), you'll barely lift your foot off the clutch before pushing it down for the 1-2 shift. Traction will also be pretty ugly. With an AOD, IIRC a 4.10 gear gives you a good first gear ratio combination with the trans. It should really help 60 foot times.
Top speed will be effected, but if the only time it will see over 100 mph is at the track, who cares?
Steve
72 Skylark
Actually a good shift point is much lower. Read on.
Even with 4.10s, he won't run out of rpms on a 1/4 mile track.
You'd think. However, the early SOHC 4.6s had terrible heads! MM&FF found the best shift points for those cars were at about 5,000 rpms. The '99 and ups, with the better haeds/cams, could probably be hung out much higher -- I'm guessing 5,500 - 5,800.
The 5.0s responded best to 5,500 rpm shift points.
Patrick '93 Cobra '83 LTD
Hence my earlier comment about 281's not being able to rev like an OHC should.
CobraJet
Yep, the early heads are some weak-breathing pieces o' crap, for sure. Turns out that the cams and intake were shitty, too. I can't speak for the AODE cars but I've done a TON of 1/4 passes, quite a bit of dyno, and stupid amounts of research on the shift points for different stages of the 96-98 4.6 SOHC when coupled to a T-45 like mine is.
For a stock version of the above mentioned years the most effective shift points come up at 5750 for the 1-2, 5500 for 2-3, and 5250 for the 3-4. Anthony S. (who used to be a regular here) was the first one to turn me on to this. I tried it and *poof* lost .25 in the 1/4 with great regularity. I was stunned and amazed. Some time later, after I had my still-stock car on the dyno I plugged the numbers into a couple of different shift-point calculators and they both came up with the same answer give or take 50 rpm. Anthony S. had clearly taken the time to do his homework.
When I added the better 2000 P.I. heads (with the obligatory port, polish, and valve work) I discovered that the stock rev limiter which was set at 6050 if memory serves, came up ungodly quick, even through the stock exhaust and its 6 catalytic converters. After more dyno data the shift point calculators pointed me in the direction of 6000,
6000, and 5850. "How very odd", thought I, for I didn't understand this perplexing result. Then it donned on me that I didn't have sufficient high rpm data to plug in and thus had to extrapolate what the values might be in the upper range. So, like a good Stang driver, I practiced getting as close to the limiter as possible without popping it, lol!One Bassani Offroad X-Pipe, Catback, and custom chip later, my rev limiter now resides at 6500 and it comes up pretty damn quick, 1st gear would still pull way past it if left unchecked. This allowed me to get dyno data up to 6500 now so I could figure shift points again with some degree of accuracy (yippee!). They are 6500 for the 1-2,
6350 for the 2-3, and 6200 for the 3-4. I'm a little nervous about running it up much higher than 6500 unless I go to a solid "lifter" setup. The DOHC's, however, can go past the 7k mark without much fanfare at all. A stock 99-04 SOHC still falls on its face pretty bad past 6k or so.Earlier? Like last year? ;) Just kidding... You're dead-on right about that, of course. However, you gotta admit, you'll always see the automotive world through Big Block-colored glasses. ;)
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1998 GT Coupe 5-spd. Bright Atlantic Blue K&N FIPK, Tri-Ax, 3.73's, FRPP Coated Shorties, SpeedCal, P&P 2K Heads, 2K Intake, Bassani X-Pipe and Cat-Back, Subframe Connectors, JMS Chip, Eagle Alloy Wheels
huh ? A stock 5.0 is in no way happy revving it that high. There's nothing left above 5500 or so. Even at 5500 , the engine is not happy. We're not talking about the rev-happy OHC engines here. It's the ole
5.0 pushrod engine.
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Exactly. The factory roller cam hydraulic lifter valve train will start to float at about 6,300-6,600'ish. So shift points should be less than that. 6K is a pretty safe point. The stock bottom end will easily survive blasts to 7K. I wouldn't run it there all day, but occasional blasts I wouldn't worry about. After about 5,200-5,500, the power curve starts to flatten out. Shifting at about 6,000 puts the engine right back in to it's power band. Some stock heads start to fall flat at 5,000. They need to be shifted sooner, as they never seem to reach 6K. Playing with a drag strip program is a lot of fun. It allows you to play with gearing and shift points to see how they compare. They are not tremendously accurate for ET's, but help guide you on equipment choices - like gearing.
Oops... I gotta correct myself here since my brain was on tilt that day (apparently). The correct shift-points for the above situation were actually 5500, 5250, and 5000. I don't know what made me think of this today but apparently some random synapse fired and I realized what I'd done.
Getting old sucks.
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1998 GT Coupe 5-spd. Bright Atlantic Blue K&N FIPK, Tri-Ax, 3.73's, FRPP Coated Shorties, SpeedCal, P&P 2K Heads, 2K Intake, Bassani X-Pipe and Cat-Back, Subframe Connectors, JMS Chip, Eagle Alloy WheelsMotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.