Mustang GT 2008 classification question

[tang-o]

I have a 2008 Mustang GT with the following modifications.

4.10 Gears
CAI with an SCT Tuner
18x9.5 wheels
FRP springs

Is ST ok? I was not sure about the 4.10 gears.

Thank you!

[breakaway500]

The 4:10 gears will bump you into SPA..IF that gear ratio was not available as an OEM differential option from the factory.

ST rules regarding differentials:

"6. Updating and backdating of differentials is allowed within the same manufacturer. Any aftermarket limited-slip differential
may be used provided ratios are among those available on OEM differentials. Welded or locking differentials are
prohibited."

You could put 3:73s in it and be legal for sure. Maybe a 4:10 gear ratio was available for an 8.8 in another year? Maybe the 2000R or possibly an option in one of the later Mustang Boss options? It would only be an issue if you were ever protested,or set a track record,so you would have to have proof of compliance to the rules in place,or forfeit the win.

[DanDarcy]

Ford does offer 4:10 gears for the 8.8 rear but they are too low. I had 4:10s in my Mustang with 18" wheels 275x35x18 tires and a rev limiter of 7400rpm. At long tracks like Watkins Glen I would be on the rev limiter down the back straight. If you haven't installed the 4:10s yet, I would go with the 3:73s.

note: 5th gear is too weak and useless in the 5 speed mustang

[tang-o]

Thank you both.

Indeed Ford Racing does offer the 4.10 gear ratios that are currently installed on this car (just bought the car). Part # - "Ford Racing M-4209-G410A"

I would prefer to run in STA and then maybe put 3.73 later on because of Dan's excellent point of top speed on 4th gear.

Mark, I noticed you are a Scrutineer. DOes that part # satisfy the OEM requirement for STA? Should I contact somebody else at COM to get the definite answer?

Thanks!

[breakaway500]

The way the rule is written,if you have reasonable proof of the available ratios for the 8.8, and it included your installed gear ratio, I would have to say no foul.

ST1,by the way...and welcome..

[dinoracer]

Emilio

2008 Mustangs all shipped with 3.31 ratio rear axle as standard; the manual transmission ONLY could be ordered with the 3.55 ratio factory installed

Although the 4.11 is a Ford part number, it was only available over the counter at a Ford dealer, never factory installed. Unfortunately, having the dealer install it doesn't count....Therefore, it's not an "OEM option" and bumps your car into SPA

That said, COM is basically self policing in terms of what class you assign yourself to - you can run in ST-1, but if a competitor calls you out, you risk being DQ at time trial.

I think you should not worry about it for the first couple events, as you're probably going to be slow enough if you time trial that there won't be any protest. If you find the hook has set, and you're going to be a regular, you'll probably want to back down to the 3.55 anyway, as you'll be riding the rev limiter a lot with the 4.11s on the longer runs ( as already mentioned).

[breakaway500]

"6. Updating and backdating of differentials is allowed within the same manufacturer. Any aftermarket limited-slip differential
may be used provided ratios are among those available on OEM differentials. Welded or locking differentials are
prohibited."

It could be argued that the above statement does not specifically say the gear ratios had to have been "installed" in a 2008 Mustang to be legal for class. The rule says any differential is allowed within the same manufacturer,earlier year,or later...and says nothing even about the design being the same ((8.8 vs 9" etc) The only limit imposed seems to be with aftermarket limited slip diffs; they must be equipped with the same ratio gears that an OEM diff has available....so,if any Ford diff had a 4:10 gearset option...ever... that seems to satisfy what may be used.

I also agree the 3:55's would be a better choice for road racing.

[nateh]

The rule in ST is that if it doesn't say it's legal, it isn't. The rules don't say that changing ratios outside the OEM equivalency defined above is allowed, and therefore it isn't. It appears to me that the rule allows the use of an aftermarket limited slip diff - and that's all the that is implied by the wording.

[breakaway500]

"..provided ratios are among those available on OEM differentials."
The rule is allowing any ratio to be used,as long as it is among those available on OEM differentials. Doesn't seem to limit it to 2008 Mustang diffs (as written)
If they are allowing updating and backdating from any year,any model..as long as it is from the same manufacturer,in this case Ford...it does seem to leave some wiggle room on allowable ratios..

[dinoracer]

Mark, I think you are correct on there being more latitude on the ratio. Under the current rule, any ratio that was available factory installed is legal; not just for 2008 ( in this case). My mistake

Looks like we could use a little refined-wording on this rule.

My interpretation of "OEM differential" in this context ( ST class), and what I think was the intention of the rule, was to allow use of any of the OEM ratios that were available as factory installed from the manufacturer in the axle that came with the car. For this case, that would mean any factory installed ratio that was available in an 8.8" axle.

I agree our rule right now allows a swap to any rear axle the car maker has installed in any vehicle - ever. In this case, you could install a 9" axle in place of the 8.8, and over 30+ years (early 60s to late 90s I think) the 9" was installed, FoMoCo probably had as an OEM install ratios anywhere from 2.50 ( 60's Galaxies) to 4.57 ( pickup trucks) available.

This wide range of "OEM availability " of ratios could then be extended to cover the 4.11s in question right now- ie: Ford did offer 4.11 gears factory installed in cars in the mid-late 60s - but that was in a 9" housing. Does that fact that a 4.11 was available at one time, albeit in a different axle design, mean it's legal in this case? On further reading, I guess our current rule says yes.

I don't think it was our intention to allow replacement of the factory axle assembly in ST ( such as swapping the 8.8 for a 9"), just to allow use of any OEM gear ratio that was available in that assembly. The spirit of ST is to get as much out of the car's OEM suspension and brake design ( upgrades allowed but no large design changes), while keeping the drivetrain close to stock/original.

In the case of Mustangs, I think if you got to the point where you were swapping to the 9", you've probably already made it into SPA with engine mods anyway....

[nateh]

Looks like we could use a little refined-wording on this rule.

Most definitely!

[tang-o]

This is good stuff!
I know I will probably go to a 3.73 gear ratio *eventually* - in the mean time 4.10 for ST1 sounds like within the parameters of the rule, right? I'm using the 8.8 housing.
I'd would like to comply with the rules even if I don't make the top in TT

Cheers!

[breakaway500]

I'd say you are good to go! Don't sweat the rules too much..(other than safety) just come and have fun...

[tang-o]

u bet! Thanks again!
I will see you at the track.
Cheers

[chaos4NH]

Because I run an econobox hatchback with a sporty stock motor that was "pushed" into ST1 by the ridiculous idea that power to weight ratio makes cars equal, I would protest the change of gear ratios as stated. Additionally, as members who attend BOD meetings well know, I am adamantly against the continual "creep" we are allowing in many cases. For those who do not attend the meetings, here are a couple of the things that give me heartburn in ST classes:
1. Engine swaps in Miatas to level the playing field. Our rules clearly state that it is impossible to gaurantee the competitiveness of any given car. So why are we leveling the playing field? In my mind, the 1.8s and 1.6s should be in separate classes.
2. Engine management systems, such as megasquirt, that totally change the valve timing, spark curve, etc.
3. The prohibition of "tuning" turbo cars as long as the stock max boost levels are not exceeded, which to me, is simply the equivalent to the engine management systems noted in #2.
4. The use any of AFTERMARKET differentials and limited slips.
5. The removal, or disconnecting, of ANY equipment necessary to pass NH (or those of the state of registration of the vehicle) safety and emission requirements.
6. Removal of air bags (which, by itself) would result in a vehicle unable to pass state safety requirements. Note: My nissan has them removed cause you gotta keep up with the Joneses, but I do not support the rule.
7. The cheating that goes on!

The idea that founded ST classes, that it was primarily a class for those street driven cars with suspension modifications and engine mods restricted to bolt on such as CAIs and free flow exhausts has been obliterated by the slippery slope of rules creep.