Changing rearend ratio on supercharged car

[cbear50]

Has anyone changed their rear end ratio out yet?

My problem is I've got the roush tune and you have to send in your vin number to roush to get the supercharged tune and wait 2days for them to email it back or fed ex them your ECM. If I change the rearend I'm pretty sure that would throw off my tune.

Has anyone gone through this process yet? If so would love to know how the process went and opinions on the the performance gains of more aggressive gearing.

Sponsored

 

[Cascadia_302]

Has anyone changed their rear end ratio out yet?

My problem is I've got the roush tune and you have to send in your vin number to roush to get the supercharged tune and wait 2days for them to email it back or fed ex them your ECM. If I change the rearend I'm pretty sure that would throw off my tune.

Has anyone gone through this process yet? If so would love to know how the process went and opinions on the the performance gains of more aggressive gearing.

You might try asking some of the vendors that have part/tune test mule cars.

 

[Project Whitemare]

It's just going to throw off the speedometer.

 

[MotorJoe]

Has anyone changed their rear end ratio out yet?

My problem is I've got the roush tune and you have to send in your vin number to roush to get the supercharged tune and wait 2days for them to email it back or fed ex them your ECM. If I change the rearend I'm pretty sure that would throw off my tune.

Has anyone gone through this process yet? If so would love to know how the process went and opinions on the the performance gains of more aggressive gearing.

I'd consider that a more aggresive gearing on a PD SC 5.0 will just produce a lot of wheel spin in the lower gears. Is that what you are looking for?

For a PD SC 5.0, I'll stick to the lower gearing option, a more aggresive gearing will only help at high speed in higher gears, but there's where top end power plays, so it makes no sense to me.

 

[phunk]

Rear end gear won't effect your tune. For the same reasons your car isn't tuned differently for every transmission gear.

 

[cbear50]

I'd consider that a more aggresive gearing on a PD SC 5.0 will just produce a lot of wheel spin in the lower gears. Is that what you are looking for?

For a PD SC 5.0, I'll stick to the lower gearing option, a more aggresive gearing will only help at high speed in higher gears, but there's where top end power plays, so it makes no sense to me.

I'm running 305's in the back and from a rolling punch in 2nd ive got full traction, now in 1st it takes a little driving skill but it's not out of control or anything. Currently running 3:31 gears and just feel like a shorter gear would make for a more lively experience in 2nd and 3rd. This is not a track car for me most of my full throttle runs are on on ramps or vacant service roads. I just think the car would pull harder from 50-100 mph.

 

[cbear50]

It's just going to throw off the speedometer.

So if I go ahead and change the gear with out recalibrating the tune i will get the performance benefits right away but the only draw back is the speedo will be off?

 

[Barrel]

Not sure how speedo is affected since you aren't changing the size of the wheel and speed isn't measured at the gears.

edit: I stand corrected.

 

[Anthony]

Speedo is from the trans. The trans is spinning more with lower gears, less with higher gears.

Mph isn't gathered from a wheel sensor.

 

[Anthony]

So if I go ahead and change the gear with out recalibrating the tune i will get the performance benefits right away but the only draw back is the speedo will be off?

Gps will be off if you have it. Auto trans with be affected too. It will work, but shift points will be off I'd suspect. I haven't looked at the auto much since I didn't buy one

 

[Reds197]

I would stick with the 3.31. It is a very good gear for Roush blowers. If you want more pull from 50-100 get a different tune. It will be night and day vs Roush tune. Roush tune is very very soft.

 

[phunk]

Seriously speed sensor is on the trans on these cars? I have never owned a car with ABS that doesn't just take it from the existing wheel speed sensors,

 

[Anthony]

Most cars are read this way.
If read from the wheel, which wheel? They don't trun the same revolutions in corners, that would give inaccurate speeds.

Even my atv gets speed from the trans

 

[cbear50]

Gps will be off if you have it. Auto trans with be affected too. It will work, but shift points will be off I'd suspect. I haven't looked at the auto much since I didn't buy one

mine is a 6 speed also so atleast i dont have to worry about shift points

 

[phunk]

Most cars are read this way.
If read from the wheel, which wheel? They don't trun the same revolutions in corners, that would give inaccurate speeds.

Even my atv gets speed from the trans

Must be an American car thing. It sounds totally strange to me because none of the cars I work on the last 10 years have a speed sensor on the trans.

Sponsored