Wow!!! I cant believe the difference! The best way to explain it is with the 3.31 my car felt kind of sluggish and lazy. It now feels crisp and quick. literally it feels like it has double the power. All the ratios seem much tighter when shifting and it is always in the power band. During the 1-2 shift I can really feel the car dig in and squat down. Third gear has way more power. What an awesome modification.

I actually had Ford do the install. For some reason they flashed my computer back to stock (I had a Brenspeed 93 tune flashed in it when I left it with them). So my first drive with it was really slow and crappy. Any bit of load I put on the engine would cause a noise to come from the back of the transmission that sounded like they installed the driveshaft wrong. I was ready to take it back to Ford, but it was so sluggish I figured it was a reflash. I think the noise was from inside the exhaust. It wasn't detonation, but some kind of backfire or something due to my C&L still being installed with a stock tune.

When I got home I hooked up my SCT X3 and checked the strategy. Sure enough I confirmed the Ford dealer put in a new strategy that I had not seen before. I then thought I would need to call Brenspeed and have them change my tune to add the 3.73 gear. I didn't know I could modify the Brenspeed tune myself and just add the 3.73s, so I figured I would just run the SCT tune for a mustang GT with a C&L cold air and 3.73s and call Brenspeed in the morning to add the 3.73s and email me the new tune.

I had one day running with the SCT 93 tune. It was simply ok. It was faster than with the Brenspeed 93 tune with 3.31s but not by much and it left me a little disappointed. I called up Brenspeed to get my tune updated and they told me how to just change the gear in my tune myself so when work got out that day I reflashed it in the parking lot.

With the Brenspeed tune the beast was unleashed!!! What a difference! I swear it feels twice as quick as it was. I cannot believe what a simple tune can do. This car reminds me of my old 93 5.0 with off the line power. It is now as fun or if not more fun that my old 5.0. My car just went from boring to fun and exciting!

Oh ya, the price at ford was $500 just for labor. It was pretty expensive but the install is perfect. No noise at all. The mechanic that did the work was really experienced with 8.8 gear changes and that's why I went with them.

 

Glad to hear your happy w ur setup. I just had 4.10's put in so I know how ur feeling. Your install was a bit high but what isn't from Ford. As long as your happy then all is good.

Have fun pulling the oils out of the ground ( since some think it's the rubber that makes the strip).

 

It is a nice Mod. My dealer wanted 800 in Labor. So I wound up at a drive line specialty shop where we wound up installing OEM gears. As quite as stock in all respects with a lot more zip.

 

I love my 3.73's in my auto, I agree it does wake things up. Next things to add are an alum DS and some UDP's to make up for the lost gas miliage and a few more ponys to boot.

 

My `11-that I may be picking up on Monday-has the 3:73s in it. Cool-that you are seeing a nice increase in the fun quotient!

 

Ya, I know it was a bit high but on my old '93 stang my brother and I installed a 3.73 one time. We thought we had it set up perfect but it howeled bad due to our inexperience. I later switched to a 3.55 that I had someone switch out for me. It howeled too. I was so worried about the howling I just went with who I thought would do the job best. I must say gears and trans rebuilds are the only thing I will leave to the professionals. All other mods will be installed by me, so this will be the only time I get bent over for an install. It is perfect right now so I am okay w/ the price.

 

Cusp,

I was reading all of your old gear posts and they are what made me decide on even switching the gear. Your posts were a huge help to me. Thanks!

Den

 

I spent about a month researching the forums looking for any tidbits and different opinions before I committed. Including playing "what if" on a gear calculator spread sheet. Then I had a long conversation with Mark at Coast Driveline & Gear. Mark is a wellspring of mustang knowledge and he highly recommended going with 3.73s for my street application. He saved me enough money on the gears under what the dealer wanted for the job that I sported for their drive shaft as well. If soft of wish I had had the two mods done separately so I could tell if the shaft made a difference I could notice. However 80% of the drive line clank is gone now and the two together were satisfying. The posts I added were my way of paying forward as by the example those before me gave.

 

I will say my next purchase will be a driveshaft for sure. I just dont know where they come up with the prices for these S197 parts. I bought a brand new Ford motorsport Aluminum driveshaft for my 93 Stang in 1995 for $179. Now they want 600 bucks for one for an S197. I guess the new ones are made of gold or something.

 

You're telling me. I have no idea why they charge so **** much for it now. Glad to read some positive experiences on this as I am thinking of the same axle ratio change too.

 

4.10 is even better!

 

What benefits do you get from changing the drive shaft?

Just curious as this is the first I have heard it mentioned with gears.

Thanks

 

An aluminum driveshaft is much lighter than the stock unit. This reduces the vehicle's rotating inertia, which gets the engine into the meat of its powerband quicker, and results in faster acceleration. Lighter wheels and tires have the same effect.

 

The S-197 drive shaft is not one piece. There is a sliding spline section with a rubber boot. What is missing is that mid span pillow block and the CV joints connecting it together. Most of the Aluminum straight drive shafts shed 25ish pounds under the stock set up. Although some of that weight is the pillow block and so would be non rotating. The older style has the sliding spline as part the transmission out put shaft. The new style does not. Part of the expense then is due to the more complex design of the shaft. And part of the cost is on the higher prices of the materials used. The older style shaft is less expensive because both are similar in design except for the materials used. But the older (less costly) version does not shed as much mass either; Only a few pounds. The benefit then would be more of improving the torque and critical rpm limitations than one associated with a meaningful reduction in rotation mass.

 

Interesting. Thanks

Will have to ask about that when I do the gears in a couple of weeks.

 

According to Ford engineers, replacing the drive shaft removes some important design benefits of the 2 piece.

Excerpts of the conversation:

***
Clunk is driven by total driveline lash, dominated by the gear sets and clutch tuning/capability. The 3.73 amplifies this a bit compared to the 3.31 and 3.55 axles. The 2-piece driveshaft is not the cause of the clunk noise. The Bullitt will have higher levels of clunk compared to the base GT. The base GT throttle response is a bit softer than the Bullitt's. The increased throttle response makes the clunk a bit easier to get. It is a trade-off - improved performance feel vs clunk.

The post mentions high speed and 160mph - The Mustang (as it leaves AAI) is speed limited well below that for a reason. Like I said before, I do not know specifics about the dynotech piece, what it does or does not do. I do know about the 2-piece in the factory car. It is a fairly robust piece. Vibration is not an issue unless the centerbearing shims are not installed properly, the shaft has a balance issue or the pinion angle is off. These would be quality issues (that I'm not aware of having in production), not design. The 2-pc has no roll in whether or not you have a random vibration. U-joint angles, run-out (flange or shaft), balance and system modal (resonance) response govern vibration.

*** 2 piece drive shaft and rust

The 2-piece driveshaft is required to meet internal engineering requirements for safe operation at max vehicle speed. Basically, it is designed to provide a driveline system resonance well above what the speed limiter will allow you to operate at. If you put your driveline into resonance, bad things may happen! I've seen what it does to a car and it isn't pretty.

The driveshaft CV joints are required components on this type of driveshaft when combined with a live axle. If the rear suspension were IRS, simple flex couplings would be used (look at the new Camaro, Challenger, etc...) and would make for a lighter driveshaft.

The driveshaft also has an internal torsional damper (ITD) which is soley there to attenuate axle whine. If package allowed, the ITD would be mounted on the exterior of the driveshaft as a much lighter ring design. Since the equivalent inertia is required out of the smaller diameter part when installed inside the driveshaft, the mass has to increase. So, you get a heavier ITD vs a lightweight ETD.

A single piece steel or aluminum 1-piece would have to be larger in diameter than the current package allows. Basically, you would have contact with the fuel tank at full rear suspension jounce. 1-piece carbon fiber was explored at one time...

Hope this helps.

Oh, and as far as the rust is concerned, we hate it too. All I can say is write lots of letters to Ford asking them to make your Mustang's steel powertrain components (driveshaft, axle, etc...) come painted from the factory because you don't like rusty car parts. Customer feedback is sometimes absolutely necessary to make a change that, to many of us, should seem so obvious and simple. Fill out those customer surveys that you get in the mail. They really matter.


I would not assume an aftermarket piece "solves" a problem. Yes, you can stuff a massive driveshaft into the tunnel but it will not meet standard vehicle engineering requirements. Our requirements take many factors into account, with the biggest one being your personal safety under a wide variety of operating conditions. Our parts are engineered to work in one big system. Aftermarket parts are generally not engineered. By this, I mean that they are designed to fit properly (usually) and improve one or two attributes specific to your application.

For example, if you want a lighter weight driveshaft that gives you less rotating inertia, you can buy this aluminum 1-pc driveshaft. But, that's all you get - lighter weight. Not proven durability, safety (how does the driveshaft react in a rear impact?, clearance to other parts like the fuel tank?), NVH, ride (driveshaft plunge force actually affects your ride quality), etc...

But that's the great part about it being your car. You get to decide what you want your Mustang to be. Just be cautious and think about how these parts may affect the rest of your driving experience, safety and wallet if it breaks or breaks something else in the car.

I've been in your shoes (which is why I became an engineer and worked my way onto the Mustang team!) and know exactly where you are coming from, though. I don't know specifics about the d/s you are referring to but I'm just giving you some things to think about and consider.

Thanks for buying a Bullitt!


*** lower control arm bracket axle masses

They are there to attenuate axle whine. If you currently notice axle whine in your car in the 45-65mph range, it may increase a bit if you remove the masses. They are one part of a fairly extensive package engineered to address axle whine on the s197 platform.

 

cdynaco, is there more to this excerpt? Link?

 

there is no link, I copied the conversation and saved. The rest is just the conversation going back and forth. What I posted was the gist of the issue concerning any clunk and the stock drive shaft.

 

Wow, my stealership quoted $1,400 parts and labor for 3.73's

 

I've been waiting for someone with this exact gear swap to post. I honestly hate the 3.31's. 3rd gear is horribly long and they make the car feel a bit sluggish. I had considered 3.90's in the past, but a friend of mine with a CS pretty much exactly like mine has them and I didn't care for them(though his was an automatic). I absolutely do not want 4.10's, so 3.73's seemed logical to me.

Den,

any chance of a video of you going through 3rd gear?