rygenstormlocke

So I got my parts, but oddly enough I checked my order (hard copy and email) and my Motive Gear box says:

F7.5-410

So, using simple logic, this part number means Ford 7.5 Rear End, 4.10 gears. Oddly enough my hard copy invoice, and electronic invoice say 3.73. Now it is possible that I got 3.73 and the box is wrong.....but I highly doubt that.

Soooooo.....now I am at a fork in a road. I sent an email to mustangtuning.com asking them if its possible my gears where boxed in a 4.10 box by mistake (i think this is unlikely though).

Now, assuming they are 4.10's.....do I....

1. Send them back, and get my 3.73's
2. Keep them and just run with it

The problem I have is I have the install scheduled, if I send them back I have to wait another week without my gears. Right now I am leaning towards keeping them, I knew I would like both gear sets for sure....I just went with 3.73's cause I thought they would work out a bit better.

:scratch:

Thomas S

If you mostly do city driving then the 4.10s would be great. If you spend a lot of time on the highway, the 3.73s would be much better.

rygenstormlocke

I do both, I commute every day to work 30 miles, half city and half highway. I counted the teeth on them, they are 4.10's.


Hmmm. :scratch:

scrming

Dang... hate to be in your shoes... it's a very tough call... If you like popping of the stop lights the 4.10s are the way to go! But if you drive on the highway at 80 MPH you'll be spinning at about 3,000RPM.... can you stand that? LOL

rygenstormlocke

Hmmm, maybe I should just buy bigger rear tires. LOL. I am leaning towards sending them back. The idea of spinning my tires at stop lights is very cool......but I do have to drive on the highway a bit. I have a 30 mile commute from Sterling VA to DC every day and my magnaflows are already very loud at 2600rpm. I will have to give mustang tuning a calll so arange a swap out.

Just so annoying they got the order wrong. Oh well......must be patient.

MSP

Did you look on the back of the gear? It shows what gear it is, 3.73 or 4.10.. Its stamped into the gear..

2629rpm @ 70MPH.. - 4.10's

2392rpm @ 70MPH.. - 3.73's

I dont know man, tough call.. Its a difference of about (237)RPM while at 70 MPH..

2817rpm @ 75 - 4.10's

2563rpm @ 75 - 3.73's

A difference of (254)RPM while @ 75MPH

A difference of 17rpm per 5 MPH..

I say keep'em, slap them in, and start rippin up the streets my man!! Doesnt look like much of a difference while shooting around town between 70 or 75 MPH..

On the 1/4 mile is where we see our biggest difference.. When you slap on the NOS, the end of a 1/4mile run is what were looking at...

105MPH @ 5259rpm 4.10's----darn good range!

105MPH @ 4785rpm 3.73's---- Not bad, but this is more for a car with either more boost, or a 150shot..

So looking at the numbers in the short to near term future, you should be ok with the 4.10's... Now later once we all get our Twin-Turbo's installed, then the boost generated at the bottom end will make the lower rpm situation ideal... For the 100shot, you perfect at 4.10 as you can see.. Up to 150shot will be needed, before the ideal 3.73 situation will be appreciated..

I say keep'em.. Unless your sticking to your guns on the 150shot, or the Twin Turbo!

rygenstormlocke

I took them out again this morning, it came with install directions, and the first section was verify your gear ratio. Had instructions for counting the ring and pinion, ring is 40, pinion is 10. I got 4.10's.

Oh well, boxed them back up. Must have patience!

MSP

I edited my post.. Check it out.. Patience is a good thing.. This means your extrememly dangerous.. Calculated... Driven... LOL!!

MSP

But do you see why I say you will need a 125 shot with 3.73's to beat Scrming, if for instance the two of you raced?

rygenstormlocke

You know what...you are a bad influence!!!!! LOL. :bang:

I know what I'm going to do, I'm going to go to the local mustang club meeting tomorrow....and see if I can find a 6 there with 4.10s and ask the person if they mind taking me for a run in the car.

I do like your numbers though....maybe I should just get a resonator for the exhaust, or spray that suff on the underside of the car so I can still use my cell phone when the wife calls.

Performance wise, your numbers and everywhere I read says you can't go wrong with both gears. It's a noise issue now. Even now, with my pred tune and maganflows, she can't hear me well in the car.

Still thinking.....you know, if I decide on turbo or twin turbo's later, whats that gonna run me.....$3000.00+.....what is an extra $200 on that, if I am at that stage....changing out the gears would not be a deal breaker.

I was just hoping to have the 3.73's in before we have our 4.0L smack down....just to see how they hold up agains scrmings 4.10s. But....you will have to carry that torch my friend.

And yes, I really am serious about all of us meeting at a track. I alreedy told the wife I will be using some of my vactation time for this.

MSP

Yes, dont get me wrong.. You fully understand all my calculations are setup for later when 12's is the norm.. Like I said before, I am shooting for 11's.. So all my gear calculations are based on this number.. I should start to see the benefit of it starting from a point of low 13's to mid 12's.. As my power increases, my engine has the ability to tach out quicker.. So this means, running a slightly larger gear than a 4.10 will be beneficial to me.. In the near to short term, I will need to keep my NOS setup one step ahead of you guys to finish before you, provided I get a good launch and dont miss any gears while chasing you.. This means, I expect you and scrming to beat me to the first 1/8th, if you guys stick your launch.. But once past the 1st 1/8th marker, all bets are off, and then my extra 25hp shot above you kicks in.. This wont place me too far ahead, but all I need is a fender or even a bumper to win.. If you run 100shot, I run 125shot. If you run 125shot, I run 150 shot.. If you run 150 shot, I'll attempt 175 shot.. In this case, I'll either beat you again by a bumper or blow up my motor.. I'm willing to blow up my motor just so you guys know.. I need an excuse.. I'm looking for one.. Dont make me blow up my motor please... I will!!

If I do, I'm not sure what I will do in regards to the engine..

What I mean is, I'm not sure what will replace it.. However, I believe it can handle a 175shot, if setup properly with a good tune..

rygenstormlocke

Don't blow up the engine man, then you might end up in a different forum. Besides, we must carry the torch on what the 4.0 can do. I'm not going to a 150 shot...that is what Scrming is for. He can safely push his car, because he has Lideo and other heavy duty resources to tap into. My area is mostly ricers, and the muscle car shops are few and far between, and they charge an arm and a leg. I'm still debating on that new shop I went to, they over charged me on labor for my tlok....ticked me off and my other mechanic is really good, but most of his work is on old muscle cars, pre efi engines and turbo diesels. But he is very good.

I'll stick with the 4.10's. What the heck, even if the car is loud, at least people will hear my 6 comming up on them. LOL.

scrming

hey... if you leave now you can be in Michigan late tonight or tomorrow... I'll let you take my car out for a spin... BOTH bottle are FULL! LOL!

MSP

Yes, I think your ok for now.. Remember that all my calculations are for above 110MPH 1/4 mile... Look at this guy, he's also set with 3.73's..

http://www.bromell.com/the_stang.htm

Now of course you can take 4.10 car to 11's.. But you understand and hope that a slightly higher RPM motor wont hurt itself.. Also, if for instance your car stops making power at a certain point, lets say 5500 rpm, and your motor is not producing anymore power, well, this means its time to shift.. Example

Lets say our engine is done making power at 5500RPM.. Just a quick example..

We have enough power to make a 115MPH pass in 4th gear..

This would place our engine @ 5760RPM while at 115MPH, with 4.10's..

Now at 115 with 3.73's, this would place us at 5240 RPM @ 115MPH with 3.73's..

So you see how important this is for later?

This is very improtant for later..

scrming

Well, when you take off from your first stop light hold on tight!!!! LOL!

Actually you are supposed to take it easy for the first few hundred miles... LOL

rygenstormlocke

Taking it easy isn't in my vocabulary. LOL. And trust me on this, I have no problem driving to mich! I will have a rear sway bar by then. I'm an auto too, so it will be interesting to see who can hook better. I probably wont put on bigger rear tires. Soooo....just form a take off stand point, here is how it will look:

Your car: 4.10's, FRTLOK, LCA's, Larger tires
My car: 4.10's, FRTLOK, Front and Rear Sway bar and GT Pnero tires

I'm really curious if the sway bars will help my launch. Have you ever put some tought on this one as you try to figure out how to get your car to hook better?

rygenstormlocke

Yep, which is why when I put a major power adder on the car I will have to change out the gears. I'm prepared for this. It's all about evolution.

Rome wasn't built in a day.

MSP

So basically, it all depends on where you want to end up.. In Scrmings case right now, with the 100shot, he's at the top of his game.. A very worthy opponent to all those who are shooting for speeds from 100MPH to 110MPH.. For the cars with which are in another bracket like 110MPH and 120MPH, these guys cant run 4.10's.. Its gotta be something bigger..

So this is where you place your longterm goals for the car.. Scrming's car still has room to break into the high twelves with his 4.10's..

Lets say he makes a pass @ 110MPH, he is effectively looking at 5510RPM @ 110MPH with 4.10's.. So he is setup perfect for this bracket of racing..

This will yield him roughly a 1/4 mile time of... It calculates out to 11.93ET.. but thats running 110MPH from start to finish.. Lets give him time to get upto speed..Which will place him at high to mid 12's.. So Scrming still has quite a ways to grow with his setup.. This is all based on 27.5in tires..

MSP

Yes, you will be ok.. I say just do it.. It was obviously meant to be for now.. Might as well enjoy the 4.10's for awhile.. Worry about the 3.73's later, if thats the way things wnd up!

Thomas S

If you try a 150 or 175 shot you're going to need bigger injectors and a new fuel pump or that boost-a-pump.