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3.73's or 4.10's

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Posted by: ladenblowfish

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?

Posted by: ONEBADMK8

I have no idea how many times this has been discussed but 4.10's, 4.10's, 410's.

Posted by: ladenblowfish

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?

Posted by: NateRW21

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.

Posted by: NateRW21

oh and yeah... 28 spline... You'd have a good deal of work ahead of you if you wanted to run 31-spline!

Posted by: kustomizingkid

If your going to take the time to swap them 4.10's with some kind of posi is the only way to go.

Posted by: NateRW21

Quote:

Originally Posted by kustomizingkid

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.

Posted by: ONEBADMK8

Quote:

Originally Posted by NateRW21

oh and yeah... 28 spline... You'd have a good deal of work ahead of you if you wanted to run 31-spline!

Not really just a carrier swap.

Posted by: MonsterMark

Quote:

Originally Posted by NateRW21

I didn't list the standard Mark numbers only the LSC (3.08 axle vs 3.27 axle).

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.

Posted by: NateRW21

sorry, you're right... I miss typed!!!

Posted by: XLRVIII

Quote:

Originally Posted by ONEBADMK8

I have no idea how many times this has been discussed but 4.10's, 4.10's, 410's.

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!

Posted by: XLRVIII

Quote:

Originally Posted by ladenblowfish

Would 4.10 be too much for daily driving?

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!

Posted by: NateRW21

Quote:

Originally Posted by ONEBADMK8

Not really just a carrier swap.

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.

Posted by: NateRW21

Quote:

Originally Posted by NateRW21

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

Posted by: XLRVIII

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".

Posted by: NateRW21

Quote:

Originally Posted by XLRVIII

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 identical.

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!

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

Posted by: NateRW21

Quote:

Originally Posted by XLRVIII

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".

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.

Posted by: ford nut

Quote:

Originally Posted by ONEBADMK8

I have no idea how many times this has been discussed but 4.10's, 4.10's, 410's.

Posted by: XLRVIII

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.

Posted by: NateRW21

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.

Posted by: XLRVIII

Quote:

Originally Posted by NateRW21

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.

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!

Posted by: NateRW21

Quote:

Originally Posted by XLRVIII

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 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.

Posted by: NateRW21

Quote:

Originally Posted by XLRVIII

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.

Posted by: XLRVIII

Hey Nate, you seem to be a person that likes to "crunch numbers".

take 2000 1/4 mile passes and 3000 1/8th mile passes and tell me how many miles of WOT that is?

Posted by: XLRVIII

Quote:

Originally Posted by NateRW21

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.

Posted by: XLRVIII

Quote:

Originally Posted by NateRW21

We removed "measured speed" from the equation by side by side pacing on the freeway on cruise control.
Once we matched speeds is when I turned the overdrive off.

Agree'd down to the ball busting splitting of the hairs level it's not 100.000% correct base on your numbers it is about 99.68% correct (LMAO)

Sorry for the "left turn spiral spin" I sent this thread into...

Posted by: NateRW21

Quote:

Originally Posted by XLRVIII

Hey Nate, you seem to be a person that likes to "crunch numbers".

take 2000 1/4 mile passes and 3000 1/8th mile passes and tell me how many miles of WOT that is?

875 miles....

and I must say, if that engine got to 360k and did about 875 WOT miles (and we're talking acceleration miles, not top speed... which is even harder on the engine)... I'm impressed and I still stick to my guns; you got hella lucky with that engine!!

Posted by: NateRW21

[quote=XLRVIII;355160]
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.
[quote]

Come on!!!! Nothin wrong with a little fine particulate metal in your oil!!! Isn't that what the filter is for?

Posted by: XLRVIII

Quote:

Originally Posted by NateRW21

that was my last official count of timeslips which was two years ago.

there is probably atleast 1000 more 1/8th mile passes on the original engine before i took it out.

I figured it was somewhere close to 1000 miles of WOT.

I dont plan on changing any of my driving habits, so we'll see how lucky I can get with this motor.

So far... 30,000 Miles and about 200 passes.

Posted by: NYC LS8

4.30s for a mod motor, IMO.

Posted by: AbrahamLincoln

dont forget how much it costs to install the gears once you have them. its not just oh let me buy some 4.10s and boom there in. its easily a thousand dollar purchase.

Posted by: XLRVIII

430's will be my next stop on the "gear gravy train". for sure!

especially after driving my friends 01 cobra w/430's.

Posted by: NYC LS8

Quote:

Originally Posted by AbrahamLincoln

dont forget how much it costs to install the gears once you have them. its not just oh let me buy some 4.10s and boom there in. its easily a thousand dollar purchase.

You're getting ripped off if you're paying a grand to have gears installed and set-up. It's routinely done around here for half of that....and that's including a new Ford Trac-Lok.

Posted by: NateRW21

Quote:

Originally Posted by NYC LS8

You're getting ripped off if you're paying a grand to have gears installed and set-up. It's routinely done around here for half of that....and that's including a new Ford Trac-Lok.

Yeah, I saw that and my jaw dropped.... in my truck I paid about $1800 to have 4.10's front and rear, eaton e-locker in the rear and rebuilt trac-lok from the rear installed up front... that's parts and labor. Keep in mind, this was when the e-locker just came out. That locker was about $800 alone; plus two R&P sets, all the install goodies, rebuild kit for trac-lok... and of course, labor for two differentials!

If you can't have 4.10's and trac-lok installed for $600-$700 out the door, you're getting the shaft big time!

Prices from summit;
28-spline trac-lok: $219.88
Motive 4.10 R&P set: $179.95 (summit set is only $120)
Install kit (approx): $100.00

You're up to $499.83 plus labor... And I know for a fact the trac-lok can be had for cheaper.

Posted by: XLRVIII

Here in houston I was just searching for someone to swap some gears into an LVC members car.

Customer supplies the parts and Labor is $200-$300.00.
Done at a ford dealership...by a well known rear end builder.

So yea.. a grand is a ripoff.

Posted by: AbrahamLincoln

i paid 300 for labor, 320 for new richmond 4.10 and new traction lock (had new carrier bearings on already) shipped- 30 bucks for new axel seals and bearings, and like 50 bucks for the lube and rest of the install kit stuff

so 700 out the door - driveshaft is not a necessity but should be done if your going to have all that stuff out anwyways, and thats how much again? 450.

thats where i got the figure :-) add the driveshaft!

best mod ever. highway - yea you can't cruise at 140 anymore... but i like my license... do you?

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