View Full Version : Dyno day, gears and stuff

01-10-2008, 03:21 PM
The Cobra is today at the Ford dealer getting a rear suspension knuckle replacement recall done on it. I have found many things on this car that tell me the previous owner did not maintain this car the way it should be. I even found one of the diff housing mounting bolts loose on it. I found there to be what I believe to be too much play in the ring and pinion, so I ordered a set of FRPP gears.

A good friend of mine is sponsoring a dyno day at the local shop so I decided to put the car on to see what is has before any mods... So far the previous owner only put on a WMS CAI. At least that is all I can tell that was done (and the light bar). The car will be going on the dyno before I have the gears installed. I don't think that I want to put a new set of gears that aren't even broke in on the dyno just yet.

Much to my suprise, the gears were shinny when they arrived. I they look like they are polished or something. Is that normal?

I also ordered a SCT X3 Flash tuner. I will be able to reset the speedo for the new gears and maybe get a few more ponies out of it.

Next month after the gears are broke in, I will go back to the dyno to see what the SCT box picked up for me.

01-10-2008, 04:54 PM
did your car have a vibration in the rear during hard acceleration or when it had a load on it like in 4th or 5th gear

01-10-2008, 06:34 PM
There was a vibration at around 55-60 mph. I am not sure it was coming from the rear end though. When I pulled the diff oil fill plug, there were metal shavings stuck on it. So I decided to be safe rather than sorry. I have also heard many times that a set of gears is by far the best bang for the buck on these Mustangs.

01-11-2008, 10:07 AM
yes your right on the gears but mine has always had a slight vibration in it at around 65 70 and since i have lowered it i can kinda feel it at a lower speed i wonder if my driveshaft is out of balance alittle. but back to the gear deal i want to get some 4:10's for the ride but i dont know what box to get to recalibrate the speedometer

01-11-2008, 10:16 AM
I talked with the guy that will install my gears before I bought anything. As for gears, he reccomended FRPP gears as he has had customers complain of gear whine from the Motive gears. I was going to buy the Motives anyway until I found the FRPP gears for $169 from Late Model Restoration.

He told me I had two choices as far as speedo correction. He said I could get the SpeedCal for about $100-$120 that just corrects the speedo, or I could get a tuner for about $400 that would do more. Since I one day hope to do more to the car, I thought the tuner was the way to go. I chose the SCT X3 flash tuner. AmericanMuscle.com has a 6% discount for members of MustangForums.com so I ended up getting the tuner for about $350. My local dyno tuner uses SCT tuning software, so with this box, I can later have the car dyno tuned without buying anything more. I was also wanting to buy an OBDII reader and this device does that as well. So I really got three things I wanted all in one package. According to SCT's web site, the NA Cobra will pick up about 15hp with their built in tune. If you have more done to the car than CAI and catback, if you order from americanmuscle, they will give you one custom tune for free, you just need to send them your mods and such for them to tune for the parts.

I am sure there are other good tuners out there that may even be better than what I bought. I feel for the price I couldn't go wrong and have the ability to tune for later mods.

Since I will be going to the dyno tomorrow, I will leave it with the factory tune and then next month go back after the gears are broke in and with the SCT baseline tune to see if the A/F ratios are off far and can tweek a bit on my own.

01-11-2008, 09:53 PM
The 3.55's I bought a couple of months ago from Ford were in a Motive box. Motive makes some of the FRPP gears from what I understand. LOL, they even had a Motive window sticker with them for advertisement.

01-12-2008, 03:35 PM
The baseline dyno run is now complete. I put down 263hp and 277tq. The car is now stock other than a cold air intake. I will be doing the ecu flash and gear install monday. Next month when we do another day like today I will run it again. Till then, here is the dyno plot.