ladenblowfish
Well-Known LVC Member
I was thinking of doing a gear swap on my 93 mark with either 3.73's or 4.10's. What is everyones personal preference? Would 4.10 be too much for daily driving?
3.73's or 4.10's
- Thread starter ladenblowfish
- Start date
ONEBADMK8
Dedicated LVC Member
I have no idea how many times this has been discussed but 4.10's, 4.10's, 410's.
ladenblowfish
Well-Known LVC Member
4.10
Thats what I thought but I wasn't sure. I still have a couple sets of em around somewhere. They are great in in my 92 GT but its a 5 speed. I did'nt know how they would be in an automatic. Now, what speedo gear will I need? Purple 21 tooth? They are 28 spline and not 31 spline axles right?
Thats what I thought but I wasn't sure. I still have a couple sets of em around somewhere. They are great in in my 92 GT but its a 5 speed. I did'nt know how they would be in an automatic. Now, what speedo gear will I need? Purple 21 tooth? They are 28 spline and not 31 spline axles right?
I won't try to direct you one way or the other... but...
If you want to see some info on gearing, take a look at the gear/intake thread in the high performance forum. If you go down far enough, you can see some specs on RPM's at speed for different given ratio's on the 4R70W as well as most of the T-56 gear sets. This will at-least give you a little perspective as to how you can expect your RPM's to change. How you interpret that for gas mileage/wear and tear is your own prerogative. (and those are accurate, mathematical equations... speedo's and tachs are not 100% accurate. So if someone tells you "well my car runs at 70MPH with 200 less RPM than what's listed there"... sorry, but they are wrong... or running larger tires!)
I didn't list the standard Mark numbers only the LSC (3.08 axle vs 3.27 axle). So if you just have a standard Mark, the difference will be greater; but end result of 3.55's, 3.73's and 4.10's are unchanged.
If you want to see some info on gearing, take a look at the gear/intake thread in the high performance forum. If you go down far enough, you can see some specs on RPM's at speed for different given ratio's on the 4R70W as well as most of the T-56 gear sets. This will at-least give you a little perspective as to how you can expect your RPM's to change. How you interpret that for gas mileage/wear and tear is your own prerogative. (and those are accurate, mathematical equations... speedo's and tachs are not 100% accurate. So if someone tells you "well my car runs at 70MPH with 200 less RPM than what's listed there"... sorry, but they are wrong... or running larger tires!)
I didn't list the standard Mark numbers only the LSC (3.08 axle vs 3.27 axle). So if you just have a standard Mark, the difference will be greater; but end result of 3.55's, 3.73's and 4.10's are unchanged.
kustomizingkid
Dedicated LVC Member
If your going to take the time to swap them 4.10's with some kind of posi is the only way to go.
I would have to argue this... it depends on what you're looking for. 4.10's are not the answer to everything. 3.08 to 3.73 is a healthy jump in ratio by itself.
If you go by the theory of "if you're gonna take the time to do it... go big" then why not just throw down on a set of 4.30's, 4.56's, or 4.88's? Hell, they make 5.18's for the 8.8 so if you're gonna do it, go all the way right?
Believe it or not, there are some people out there who want to cruise down the highway a couple hundred miles everyday at 80 MPH and NOT have their relatively large displacement, entirely CAST engine spinning at just south of 3000 RPM (2751 RPM w/factory diameter tires to be exact). For reference, the reason those tiny V8's are able to rev so high is due to the lower weight of their reciprocating mass inducing much less stress on the connecting rods and crank
I also don't agree with your posi statement (I'm about to split hairs... sorry... oh, btw... posi is a brand, not a type of diff... I know your implied meaning was limited slip). For some people, a limited slip is of almost no value and they want a locker... Yet for others, they have no need for a limited slip and just need to repair their rear-end and maybe get a bit more gearing advantage so they can tow their 3 million foot yacht.
ONEBADMK8
Dedicated LVC Member
Not really just a carrier swap.
MonsterMark
Dedicated LVC Member
Not to split hairs but I believe ALL LSC Models came with the 3.27 gearing, whereas the non-lSC models came equipped with 3.07 gears. At least that is what the stamping on the case indicates.
AMEN TO THAT GENO!!!!
I've said this many times...
I went from 307's to 373's and was severely dissapointed in how little change there was in the car, especially under hiway cruise conditions.
I did what many do, and I "erred on the side of caution" and went with the 373's.
hindsight being 20/20 I wouldn't hesistate for a second to install ATLEAST 410's in my car if not 430's.
At the point I am at now, going from 373's to 410's would be a waste of gear lube considering the trouble and expense.
If I pull the diff back out of my car it's going to have ATLEAST 430's!
It is very easy for you to make this call yourself.. with your own car.
Get out on the freeway to your usual/desired cruising speed.
The switch your OD off.
The RPM's you are turning in 3rd gear w/307's is identical to the RPM's in 4th w/410's.
Buddy of mine has a 410 car and we set our cruise controls while out on the freeway, then I switched off the OD and our RPM's were indentical.
So, get out and give it a shot and decide for yourself.
Now with that said..
You will LOVE 410's in a city driving scenario, the car is much more responsive on the bottom end... you'll LOVE IT!
Okay, a carrier swap with new flanges would do it (or just a side gear and bearing swap)... but are the 00-up 31-spline cobra flanges running the same bolt pattern as the 28-spline? From everything I've seen, you must upgrade the splined flanges to run the larger axles of either the 00-01 cobras or the even bigger axles from the 03-04 cobras. Then you're looking at also having to replace the wheel bearings as they are a different size as well.
Anyhow, the real benefit to higher spline count is over-all axle strength... so if you were able to upgrade to 31-spline flanges and retain the factory half-shafts, well you're not REALLY gaining much because the drive-train is still only going to hold as much torsional load as your factory half-shafts can tolerate.
Eitherway, to do it RIGHT... would be a good deal of work and a healthy chunk of change.
My moronic self figured that RPM with 255/60R16's... Not sure why I did that.... but the corrected RPM at 80 MPH with factory sized tires and 4.10's would be 2897 RPM
IMHO 2900RPMs at 80MPH is well within my "tolerance level".
Then again, my non-overdrive(c-4 trans) mustang with 410's was turning close to 4K at 80...
it would hit 6500 right at the finish line which was "right in the sweet spot".
Then again, my non-overdrive(c-4 trans) mustang with 410's was turning close to 4K at 80...
it would hit 6500 right at the finish line which was "right in the sweet spot".
Not trying to bust your balls.... but, that isn't a mathematically accurate statement. Check it out:
4R70W ratios:
1st: 2.84:1
2nd: 1.55:1
3rd: 1.00:1
4th: 0.70:1
RPM's at a speed of 80MPH in 4th gear:
3.07: 2183
4.10: 2897
RPM's at a speed of 80MPH in 3rd gear:
3.07: 3119
4.10: 4139
This doesn't really hinder your cause; the reality is the RPM's would be 222 RPM lower than your "test"... which isn't a bad thing.
And as a side note, I ran the numbers for a 4.30 rear-end as well:
Speed in each gearing at 5000 RPM:
1st: 32
2nd: 59
3rd: 92
4th: 132
6000RPM, 4th gear: 158 MPH
RPM at speed in 4th gear:
55: 2089
70: 2658
80: 3038
And that's the point... what is your tolerance level?
There are trade-offs to any gearing selection; factory 3.07's give you highway mileage and possibly a longer engine life... but at the cost of acceleration. As you move up to 3.55's, 3.73's, 3.90's, 4.10's, 4.30's so on and so fourth you start to get the benefit of better acceleration, but at the cost of mileage (granted, there may be a point in there where you're improving upon the factory... just depends), and increased engine wear/potential for damage.
It's all about to what extent the trade-offs are okay with you... some people wouldn't dare modify a car... others wouldn't hesitate to drop in 4.55's and see what kind of abuse she'll take... most people fall somewhere between the two.
ford nut
Local nut case
I wonder if my 245-50 and his 225-60's created the differences you are seeing in your math.
I know there wasn't "a measurable" amount of difference looking at the stock tachs which have been known to be quite a bit in error.
373's running on 245.50s are closer to a 390 gear than a 373 from what I have found.
mathamatically you may be correct, but in a real world scenario 200RPM's is almost immeasurable on a stock tach.
While this might not be accurate to the "inth degree" it will give someone a good "fair" amount of insight if 410's are "too much gear".
comparing 373's to 410's is like a cup of coffee with 3 scoops of sugar compared to 4 scoops of sugar, one is definatley sweeter than the other, but not by a large margin.
I know there wasn't "a measurable" amount of difference looking at the stock tachs which have been known to be quite a bit in error.
373's running on 245.50s are closer to a 390 gear than a 373 from what I have found.
mathamatically you may be correct, but in a real world scenario 200RPM's is almost immeasurable on a stock tach.
While this might not be accurate to the "inth degree" it will give someone a good "fair" amount of insight if 410's are "too much gear".
comparing 373's to 410's is like a cup of coffee with 3 scoops of sugar compared to 4 scoops of sugar, one is definatley sweeter than the other, but not by a large margin.
all of that being said... I had a Porsche when I was in Germany; I'd regularly run this car in the 4000-5000 RPM range for quite a bit of time (if I had enough open road, i'd peg it out at 6200 redline as long as I could). But that's an entirely different animal. There is no way that I personally would feel comfortable running a factory built 4.6L with cast components over 2500 RPM on a continual and daily basis for an extended period of time. 3000 RPM would certainly be out of the question for me.
Don't get me wrong... I love Ford; but some things, they were just never built for.
Don't get me wrong... I love Ford; but some things, they were just never built for.
I put 373's in at 68,000 miles and took the original engine out of my car at 360,000 miles... additional wear didn't seem to be much of an issue.
Had my original engine not lost one of the cam chain tensioner pads {was still running) It likely would have easily made it to half a million miles!
I've said it many times.. DO NOT FEAR THE GEAR!
I totally agree... the tire size could make up for most of the difference, and the factory tach and speedo certainly are not test unit accurate!
Also agree on the last paragraph. In reality, it's a .32 difference; nothing monumental... but still a little noticeable.
This is where you and I differ... You may have just had some freakishly good luck...
On a side note... with 360k already on the clock, I think I'd have been tempted to just keep running and see how long I could push it. What's the worst that could happen? Chain breaks or jumps off? Big deal... so you have to rebuild the engine (as if it wasn't starting to get a little worn anyway) and maybe replace a front cover.
I wish I could say I had good luck, but I've always had "worst case scenario's" with 99% of the stuff I mess with.
Unless with this particular car, all my bad luck has been offset somehow by the "luck gods".. I dunno.
With that said.
I drove the car for 25,000 miles after the tensioner pad "gave up".
it was the secondary chain tensioner and it only "made noise" on start up.
it wasn't the ordinary chain rattle, sounded like a chainsaw cutting thru some sheetmetal... it was the worst sounding "running motor" I'd ever heard.
I wanted to "drive it til it dropped", the only thing I could see happening was it was putting ALOT of grey crap in my oil, which you and I both know is a very bad thing..it would cloud up new oil in about 600 miles.
in the end I just had to pull the motor and make my car "dependable" again, so i swapped it out.
I was still running the car in at the dragstrips street stock points program so during the time it was making all the noise I was making 15-20 passes a week in the car.