Mustang Rear End Talk

jakepressley · **Posted:** Thu Jan 15, 2009 5:45 pm

I like Redline in my Mustang, although my mustang is old enough to drink this year... and I'm not up on what makes the new generation happy.

I run MT in my T-5 and shockproof in the rear end.

I'd aviod changing gearing before tracking it and getting a baseline. I'm running 373's in the rear and dip into 5th way too soon (before the bridge at VIR). I'm going back to 273's when the bank account gets infused... It should turn my car into a 4 speed, but I'll be able to stay out of overdrive.

steve remchak · **Posted:** Thu Jan 15, 2009 10:56 pm

jakepressley wrote:

I like Redline in my Mustang, although my mustang is old enough to drink this year... and I'm not up on what makes the new generation happy.

I run MT in my T-5 and shockproof in the rear end.

I'd aviod changing gearing before tracking it and getting a baseline. I'm running 373's in the rear and dip into 5th way too soon (before the bridge at VIR). I'm going back to 273's when the bank account gets infused... It should turn my car into a 4 speed, but I'll be able to stay out of overdrive.

off topic i know, but Jake how much before the bridge are you shifting into 5th? i generally try to be in 5th gear before the uphill esses in the BMW. 3.64 LSD. were it me Jake, i would be more concerned about the braking zone into 14. are you running out of rpms down the backstretch?

jakepressley · **Posted:** Fri Jan 16, 2009 2:24 pm

Sorry for the hijack

I'm not running out of RPM's its just that 5th seems to be a lame duck. The car pulls best in 4th which is a 1:1 drive from the tranny. I often enter the uphill esses at around 90-100 (in fifth) and when I drag the brake at 10 I'm lucky if I'm at 105. I'm only pushing 130 comming into rollercoaster, with a bunch more left within the powerband. Instead of bumping my ratio to a 4:10 and breaking overdrive, I'm looking for a OEM ring and pinion to elimate overdrive all together.

but I'm open to suggestions

steve remchak · **Posted:** Fri Jan 16, 2009 5:03 pm

jakepressley wrote:

Sorry for the hijack

I'm not running out of RPM's its just that 5th seems to be a lame duck. The car pulls best in 4th which is a 1:1 drive from the tranny. I often enter the uphill esses at around 90-100 (in fifth) and when I drag the brake at 10 I'm lucky if I'm at 105. I'm only pushing 130 comming into rollercoaster, with a bunch more left within the powerband. Instead of bumping my ratio to a 4:10 and breaking overdrive, I'm looking for a OEM ring and pinion to elimate overdrive all together.

but I'm open to suggestions

the exit of 5a and Oak Tree have a profound effect on the speeds at the points you mentioned Jake. as it is, those are respectable speeds. of course if you were to "trade-up" and get a vette. :twisted:

Ryan Holton · **Posted:** Fri Jan 16, 2009 5:53 pm

steve remchak wrote:

of course if you were to "trade-up" and get a vette. :twisted:

How do you know how fast a vette can get on track?

steve remchak · **Posted:** Fri Jan 16, 2009 6:14 pm

Ryan Holton wrote:

steve remchak wrote:

of course if you were to "trade-up" and get a vette. :twisted:

How do you know how fast a vette can get on track?

i've been passed by many while driving mine. :cry:

them things is fast. :evil:

besides all that Ryan, my Z06 is officially retired to live out the rest of its life as a street slut.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Jake,

Give me the ratios for your 5 speed for each gear. Diff ratio. Tire size on the rear and/or diameter. Your preferred top rpm or where the rev limiter hits. I've got a spreadsheet I can just plug it into and plot speed/rpm in each gear in 5mph increments. We can figure out what ratios will do for you. On the C5 the factory diff is 3.42. 4th gear is 1:1. I can just make it to about 145 in 4th. My tires are probably a bit taller than yours. 2.73 might be a bit low, numerically, and you may loose more grunt than you want. I know the C5 guys that run 3.73 and 3.90 gears need 5th on VIR and RA back straights.

Graham

jimpastorius · **Posted:** Sat Jan 17, 2009 9:51 am

y'all really should split this off into another thread.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

Jake's problem is that 5th on the T-5 in a Fox body Mustang is 0.68:1.

Jake, PM me with your real email address, and I'll send you my RPM to MPH spreadsheet. Ford played around with 1st gear ratios from year to year, but I'll bet 3rd and 4th were always the same.

If you're running stock heads, then your power peak at 4800 RPM gives you about 130 in 4th with 2.73s, and 115 with 3.08s. If you have Cobra or aftermarket heads and can pull to the 5900 redline, then you have 160 (theoretically) for 2.73s and 141 (again, theoretically) for 3.08s.

jakepressley · **Posted:** Sun Jan 18, 2009 8:27 am

Great!!! sorry for the late reply, playing nurse to a house full of influenza zombies.

thanks for all the great information. I'm going to look into the specs of my T-5, as its been rebuilt, and PM a few people when I can get the facts straight.

I'm not trying to be ricky racer, but there is something comfortable about carrying more RPM's at higher speeds. I feel like I have more options in controlling the car within its powerband. Plus with my current gearing getting to 100 is no problem, 100-130 takes forever.

On to the paperwork...

jimpastorius · **Posted:** Sun Jan 18, 2009 9:49 am

I would not drop to 2:73's in the car. I run 3:73's in the Camaro with the T5-WC transmission. I always have the options for 5th at VIR. I use it on occasion on the back and front straights to give the motor a break and a little cooling.

As Art mentioned, your real issue is with the 5th gear in your T5. They make aftermarket gears for the T5 that would probably be a better solution. The 5th gear is suppose to be an easy replacement.

I eliminated the shift on the bridge straight and just the car run.
Eliminating that shift knocked a few 1/10ths off my lap times. But when racing or qualifying, I will let the car run and will not use 5th. Any thing to eliminate a shift or two per lap is very helpful.

I have 3:42 gears in the garage and another rear housing waiting to go into the Camaro. Not sure if it will happen this winter since I am in the process of moving the car to CMC2 for 2009. Most of the Mustangs, if not all, in the Camaro-Mustang Challenge are running 3:42 or 3:23 gears. No one I know is under the 3:23.

jakepressley · **Posted:** Sun Jan 18, 2009 6:46 pm

I have tried to keep it in 4th on the uphill esses and end up feeling like I'm going to blow my engine sky high... 6,300 RPM is a lot to ask, every lap, from a mildly stock push rod engine... gotta shift for now.

I like the idea of changing the overdrive gear within the tranny. I was going to pick up a spare t-5 tranny. I'll have to look into kits. Might be a good way to learn how to rebuild a transmission.

Jim-
whats the biggest difference between CMC 1 or 2? I've got to spectate at a NASA event this year.

jimpastorius · **Posted:** Mon Jan 19, 2009 8:50 am

jakepressley wrote:

Jim-
whats the biggest difference between CMC 1 or 2? I've got to spectate at a NASA event this year.

The biggest difference is the power level. With CMC limited to 230/300 and CMC2 to 260/310. For 2009, they are allowing the Fox bodies and 3rd gens to move up with a few modifications. For the 3rd Gen's I can run 1.6 roller rockers and shorty headers. Last week, the Z hit the dyno with the rockers in place and head work and put down 247/317. So with the headers, it should easily makes the numbers for CMC2.

Another allowance for the 3rd gen was the ability to put the 5.7L TPI into the car (they came in the Camaro, but only with an automatic). For this allowance, they grouped the 5.7 and 5.0 into a separate power table. The power was 240/330. No way in hell, is the 5.0TPI going to make those numbers. So with my dyno results, it appears the 5.0TPI will slide into the normal CMC2 power table.

Also in CMC2, we can go with 17x9.5 wheels, 275 tires and 13" front versus the CMC 16x8 wheels, 255 tires and 12" front brakes. For the first half of the year, I will be running the 155/50/16 tires as the money is not there to put the ZR1 wheels on the car quite yet.

If you are interested, a decent CMC2 Mustang is for sale in VA....$5000 for a turn key race car!

Vincent Keene · **Posted:** Mon Jan 19, 2009 10:56 am

jimpastorius wrote:

For the first half of the year, I will be running the 155/50/16 tires as the money is not there to put the ZR1 wheels on the car quite yet.

Yeah, those 155 tires should be cheap, but I don't think they make them for 16" wheels do they? :wink:

jimpastorius · **Posted:** Mon Jan 19, 2009 11:07 am

Vincent Keene wrote:

jimpastorius wrote:

For the first half of the year, I will be running the 155/50/16 tires as the money is not there to put the ZR1 wheels on the car quite yet.

Yeah, those 155 tires should be cheap, but I don't think they make them for 16" wheels do they? :wink:

it is Monday morning! Actually the 255/50/16 is only $10 cheaper per tire than the 275/45/17. But add in the cost of the new wheels and required spacers...

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