Top Speed with 4.10's?

[Booger]

What's the top speed with 4.10's? I was just wondering about going with lower gears. (something like 4.55/4.56?)

[SergntMac]

Max ratio in the 8.8 housing is 4:33

I haven't seen my top speed, but in 3rd gear (OD off), 6000 RPM is 120 MPH.

[03 Merc]

Booger,

Ford Racing Parts makes and sells 4.56's for the 8.8 but that might be a bit steep for the street...

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3366&prmenbr=361

If you go to the site links section you will find a link to Evil Jim's Marauder Gear Ratio Calculator that will help you with the RPM estimates..there is also another link under General Automotive that may help..

HTH

[Booger]

Thanks 03Merc, I also need to keep in mind that when I put too large a ring and pinion into too small a carrier, I run the risk of having a weak pinion shaft.

The 0.7 overdrive automatic will tolerate a lower gear ratio, that's how I got away with 5.14's in my truck. It's still totally drivable on the highway, it just doesn't get very good mileage. I can still break 100mph in it, but just barely. =(

[Colin]

Top speeds based on a 6000 redline, stock tires and 4.10's.

1st- 44mph
2nd- 80mph
3rd- 124mph
4th- 177mph

If you want the numbers for any other ratios send me a PM and I'll figure it out. If you've changed tires or had a chip that changes your redline tell me so I can get the speeds accurate.

Colin

[Colin]

Ok I'm bored. Here's top speed based on a 6k redline, stock tires and 4.33's.

1st- 41mph
2nd- 76mph
3rd- 118mph
4th- 168mph

Colin

[TripleTransAm]

Originally posted by Colin
Ok I'm bored. Here's top speed based on a 6k redline, stock tires and 4.33's.


Those are of course only theoretical numbers, as the engine would have to deliver to the wheels enough power to overcome the increased aerodynamic drag at those speeds. Also, knowledge of the engine's power curve is necessary since the engine might actually hit a spot in the highest gear where output power matches aerodynamic losses, and hence cannot accelerate any faster.

An example of this is my 1998 Ram Air Trans Am. The 0.50:1 6th gear combined with the stock 3.42 rear *should* yield a stupidly high top speed at redline in 6th, but in reality, the powertrain is not able to put down enough power to overcome the aero losses at those high speeds. Top speed actually arrives in 5th at around 175 mph (the stock computer limits it to 162 mph but I've personally seen a 1999 Firehawk with the same drivetrain top out at 175 mph with the limiter removed). Shift to 6th, and the reduced torque multiplication of 6th gear will cause the car to slow to something like 130-140 mph.

There's a nice program floating about the web called CarTest that allows you to input detailed values for engine power at 500 RPM steps and also specify items like frontal area, height, ground clearance, coefficient of drag, gearing, weight, etc. etc. etc. and it will do a fair job of computing top speed and various performance readings (0-20,30,40,50,60etc. 1/4 mile, etc.). Would be interesting to see what the MM numbers would generate.

[Logan]

If I had to do it again, I'd probably equip the car with 4.33's personally...

[03 Merc]

Logan,

Why not the 4.56's? It isn't that much of a jump from the 4.30's...

[Booger]

OK. Now all we need is a guinea pig.:P

[Colin]

All my numbers are based on what the car can due with it's redline and gearing while sitting still. It doesn't take into affect wind resistance. Technically the car can still go the top speed I said, but only with more power.
My car runs out of gear at 151, but I know damn well that it can never make it due to its aerodynamics.

Colin

[TripleTransAm]

Originally posted by Colin
Technically the car can still go the top speed I said, but only with more power.


More power... truly the answer to all life's problems! :D

If someone can provide me with the hard numbers on the MM, I can plug it into CarTest tonight and come up with some theoretical top speeds with various rear ends (on the car, that is).

What I'd need is:
Car weight (specify if curb, with person, etc.)
height, width, ground clearance
Coefficient of drag
tranny gearing (I think I can find this on the Ford.ca web site)

Also: if someone could provide me with a link to a stock MM's dyno curves (preferably one of the members' cars, rather than a pre-chipped test mule that may or may not be performing to spec). For the heck of it, I'll accept a mildly modded (ie. chip, etc.) dyno chart, but as for SC'ed MMs, well that'll be kind of pushing it.;)

Oh, and if someone could clue me in on what an unrestricted stock MM pulls top-speed-wise, that will help me fine-tune the simulation, such that it will be valid once I start swapping diff ratios or adding power.

Thanks. Should be a fun exercise if I can get all the relevant data.

[Booger]

Coefficient of Drag (Cd) 0.385
Curb Weight (lbs.) 4195
Overall Height 58.9(inches)
Overall Width 78.2(inches)

Trans Ratios
1st Gear 2.84
2nd Gear 1.55
3rd Gear 1
4th Gear .7

Not sure about ground clearance.....

[SergntMac]

Originally posted by Logan
If I had to do it again, I'd probably equip the car with 4.33's personally...

I hope you will be doing it again, Logan, and soon too. Until then, I agree with you, and I may be gearing up to 4:33 soon myself, now that a more specific purpose for my MM has come to the surface for me. I didn't start out wanting to mod my MM this way, but the fire has ignited, and I've got some ideas I'm wanting to try.

However, keeping in mind that the average owner/driver here just wants some decent punch from what will serve as mostly a family car, and overall drivability is still a strong concern, the 4:10s seem a perfect ratio in a "sweet spot" sort of way. The best performance, in a wide variety of situations, from stop light fun to long distance road trip stuff, comes from the 4:10, IMHO.

I think a 4:56 in an 8.8 is stuffing it just a bit, but that's me, and surely not with the stock differential. As my power increases, it's not just a gear ratio to consider, but durability of associated components. This is a lesson I did learn 30 years ago, with 10 and 12 bolt Chevy banjos, hardened axels, bearings, seals and so on. I have ripped them apart, and I mean really into pieces. So, if I want a higher ratio for a specific reason, and I've got power to deliver, I should probably overhaul the whole back end, with that specific purpose in mind. Stuffing the 8.8 with a 4:56 and 300 or better true RWHP just doesn't sit well with me, in terms of durability. Stuff will twist up and snap, under the weight of a heavy car with good to best traction, IMHO.

As far as these "calculating programs" are concerned, they seem somewhat accurate to real world applications. The calculation of 3rd gear top speed with 4:10s was offered as 124 MPH. I got a certified 120 MPH at 6000 RPM and 4:10s, close enough for government work, eh? And, thanks, Colin!

In all your adventures here, gentlemen, remember to consider the inherrent strength of the parts you select for modification.

Good Lord, isn't this MM a whole lotta fun?

[WolfeBros]

You guys are killing me......I gotta do the 4:10's soon !
I was going to wait until I had about 5k miles. I am currently at 2.2k
Have to take her in tomorrow to get the steering wheel replaced.
I had one where the leather was coming unbound around the right spoke. :rolleyes:

[TripleTransAm]

Alrighty, thanks to some numbers posted, I arrived at some interesting results in the simulation software I was referring to.

Now, the important thing to consider is that I haven't pumped in the exact power curve numbers yet, since I haven't had time to look around the site for some of the posted charts I've seen. I just plugged in the factory numbers of torque and hp, and the program is able to "guess" at a torque curve.

The results are interesting... the initial pass shows a theoretical top speed for the 3.55 gearing as 135-ish in third. Interesting to note is that this top speed looks like it comes in 3rd, and not 4th... upshifting to 4th looks like it would slow the car down to 125 mph or so.

Now, this is dependant on the real power curve ie. how fast it drops off after the power peak of 5750 RPM and how flat the torque curve is BEFORE the torque peak RPM. Anyways, it's a start...

[Booger]

It would be interesting to see the numbers with the other available ratios.... 4.10, 4.30, 4.56

[TripleTransAm]

Originally posted by Booger
It would be interesting to see the numbers with the other available ratios.... 4.10, 4.30, 4.56

Ask and ye shall receive. ;)

This next plot is the same power curve but with the 4.10s. Interesting in this one is that the increased torque multiplication of the 4.10s versus the 3.55s results in the theoretical top speed now being achieved in 4th gear.

The power curve for 3rd gear (cyan colored) intersects the losses curve (purple) at a lower road speed than it did with the 3.55s, where it seems you could wind out third all the way to redline and intersect the loss curve right at the very end, making the most out of 3rd gear.

With the 4.10s, it looks like 130 mph is achievable in 3rd, but then you pop it into 4th and are able to squeeze off another 5 mph or so. Funny, this is exactly the same top speed as what I obtained in my 3.55 geared plot! :) The 4th gear curve is the red one, by the way.

Now, during dinner just now, it occurred to me I a$$umed a redline of 6500 RPM. Is this correct or am I off? If I am too high, then I'll need to chop off a bit off the edge of the curves, and this might drop the actual top speed on the 3.55 curve, since it seems to arrive in 3rd at around 6500 RPM. It shouldn't change the results of the 4.10 plot, since top speed seems to occur in 4th way below redline.

Here's the 4.10 plot, I'll redo both once I get more detailed power curve numbers (a bit later tonight, right now I have to entertain a certain 16 month old bouncing on my lap eager to visit the SesameStreet.com website!)

[Booger]

Originally posted by TripleTransAm
......right now I have to entertain a certain 16 month old bouncing on my lap eager to visit the SesameStreet.com website!)


That definitely takes priority my friend. I have a 24 month old and my wife says "no more". I will enjoy this one for all it's worth. ;)

[TripleTransAm]

I found a closeup pic of the instrument panel which indicated a redline of 6000 RPM, not 6500. Funny enough, this doesn't change the top end results appreciably for the 3.55 curve, although the 2nd gear curve no longer intersects the 3rd gear curve. This means that there would be a slight gain in performance if more of 2nd gear was to be useable. As it is, it seems you're better off using ALL of 1st and 2nd gears as long as we use the simulated power curve.

For the 4.10 curve, it seems the 3rd gear curve is shortened by the 6000 RPM redline such that it won't intersect the losses curve. So this would imply the engine will wind out to 6000 RPM in 3rd before reaching top speed (it will be close, ie the car will not be accelerating all that hard, but it will run out of RPM before topping out).

4th gear top speed with 3.55s and 4.10s is still the same (obviously).

[Vince Gortner]

No way! I was all excited that I ordered my stuff from Dennis and I found a local wrench that will do the gear job for me.

Now it's time to jump to 4.33's already??? :confused:

How will I ever be as cool as you guys? I've got my hands full just trying to keep the car clean so far...

[SergntMac]

Originally posted by Vince Gortner
No way! I was all excited that I ordered my stuff from Dennis and I found a local wrench that will do the gear job for me. Now it's time to jump to 4.33's already??? :confused:

Don't be, Vince, a lot of this thread is just brainstorming the possibilities. The 4:10s remain the gear of choice, and the best choice between performance and driveability. I mentioned I want to change, but I have something else in mind, and my MM is my leisure car, I won't be driving her for everyday business, as many of our friends here have to consider.

[Leadfoot]

Originally posted by SergntMac
Stuffing the 8.8 with a 4:56 and 300 or better true RWHP just doesn't sit well with me, in terms of durability. Stuff will twist up and snap, under the weight of a heavy car with good to best traction, IMHO.

There's nothing to worry about with the 4.56s. Plenty of Mustang guys run 4.56s without too many problems. Some switch to 31 spline axles. They're able to do 5k+ rpm dumps at the tree over and over again.

FWIW, 8.8" ratio is 4.30 and not 4.33.

For Mustangs, if I remember correctly, the top speed of a stock 99, 01 Cobra is about 140 in 4th. Changing to 4.10s and no other mods raises it to about 155 in 5th. 4.30s are less than 155.

Almost all Mustang owners prefer nothing lower than 4.30s. I have 4.10s and I am happy. You can always change to a 9" and run ~7.11 gears.

[TripleTransAm]

I just ran a couple more simulations based on that approximate power curve. With 3.55s it claims a 0-60 mph time of low 7s with a 1/4 mile time of 15.2-15.4 @ 93-94 mph. The simulation leads me to believe that the MM benefits from a rip-snorting all-out high-stall launch, so I suspect that those of you with upgraded torque converters are probably making use of this ~3500 RPM desired launch. Upshifts should occur at redline, ideally according to the simulation.

Now, with 4.10s it seems the 0-60 is greatly aided, at 7 secs flat. 1/4 mile actually seems to remain the same and top speed remains the same as well, although it is now achieved in 4th instead of 3rd.

4.30s would seem to actually add perhaps 1 mph to the top speed, probably attributed to the fact the motor likes RPM and the 4.30s manage to multiply the torque sufficiently to get the motor to climb to that higher RPM where it makes more power. This may not be a valid point once I replace the assumed power curve for one based on a real dyno result... it looks like the real MM power curve might be flatter near the torque curve peak than what has been assumed by the software I'm using.

Now comes the fun part: :D
If I add the supposed increases from a 'chip', I now get 0-60 times of mid to low 6s (closer to 6.5) and quarter mile times of 14.4 seconds give or take a tenth, at 95-97 mph. Top speed climbs to 143 mph in 3rd, all this with 3.55 gears. 4.10s bring the 0-60 down to about 6 flat, and top speed is now in 4th about the same speed.

I wonder if any of this jives with real-world experiences out there? If not, I'd like to know so I can tweak the simulation some more.

[SergntMac]

3TA, there are plenty of dyno stats posted here, in a variety of threads. There are also JPEGs in the gallery for some early runs. I find your calculations interesting material to consider, and I can see how you may come to whittle everything down to a "real close to" the real world. My sig has my stats on the 0-60 and 0-120 times, maybe they will help?

[Mike M]

I have the chip and 3:55s. I will race it on opening day (first week of March). Then I will install the 4:10s.
I am hoping 14.5 with chip and 3:55s and 14.30 with the 4:10s.

[TripleTransAm]

Originally posted by SergntMac
My sig has my stats on the 0-60 and 0-120 times, maybe they will help?


Cool, I did not see that. Looks like the 0-60 estimate came real close!!

I'll look for the dyno plots tonight... I would have done it the first night I played around with this experiment but it's tough to get a whole lot done with a 16 month old bouncing on your lap. FWIW, he really enjoys it when I play the two video clips of the KB-SC'ed MM doing those smoky launches in a parking lot.

So far, the only real shortcomings I've found with this program is some inconsistencies with respect to the performance impacts of different rear end gears. While the 'hard' numbers are on the money (RPM vs. speed vs. aero losses), it's the 0-60 + 1/4 mile etc. that leave me not 100% convinced of the accuracy.

But there are enough parameters that one can tweak to get as close as possible to real life. I'm a big believer in this sort of simulation... back in University, I was able to model the entire performance (incl. top speed) of our electric car project and ended up *right* on the money... all of this on an HP 48SX calculator! (great irony of life: I still have the program on my calculator as of last week, but have since forgotten how to use it. :( :(

[SergntMac]

3TA...

I'm not a "what if" guy, I like working with facts that are supported by research and doc*mentation. But, I do admire your effort with the software, and I appreciate your results. So, if you don't find what you want to see here in a search for dyno numbers, drop me a line at SergntMac@aol.com and I'll forward some JPEGs of my dyno pulls, if you think they will help you.

[TAF]

Or...they can come get in the car with me.....no Dyno....no software....

just a special place of long, flat asphalt that I know of along one of my regular trips

I'll prove to you where it will top out...."been there, done that":burnout:

[CRUZTAKER]

No doubt Tod, I can't wait for spring tire change. I have NEVER run her w/o snows. Sucks to buy one in January up north. I want to 'been there done that'.....

[TAF]

CRUZ,

She is smooooooooooth.....