How much top speed lose?

**Ramairgod** · 12-03-2005, 07:20 AM

I have a 02 WS6 A4. If i put 3.73's in it then how much top speed would i lose? As of right now the fastest i have been in my car was right bout 150-155. Also around here, if we do set up a race, its on the interstate, so do u think this would more of a "helpful" mod or a "hurtful" mod...

**Sarge** · 12-03-2005, 08:54 AM

Do you have a stall?

**Zboner** · 12-03-2005, 09:31 AM

get a stall and be happy

**Ramairgod** · 12-03-2005, 09:11 PM

Nope, no stall. If i did get a stall then how much could i launch on street tires?

**drone14** · 12-04-2005, 03:15 AM

What is the factory diff ratio? The top speed will be related to original diff ratio divided by new diff ratio.

For arguments sake:

Original diff ratio: 3.50
New diff ratio : 3.73

Original speed at 6000rpm: 150mph
New speed at 6000rpm: ???mph

3.50 / 3.73 = 0.938

New top speed = 150 x 0.938 = 140.75mph

I am pretty sure this is how it works and anyone who knows better can correct me.
This is only theoretical and doesn't take into account stallies (I don't own an auto so I don't know what effect they have) and real world situations.

Having upgraded my diff ratio from 3.46 to a 3.91 I would highly recommend it.

**Ramairgod** · 12-04-2005, 01:25 PM

Yea i think ill keep my stock gears and just get a stall

**oneBADDz** · 12-04-2005, 04:39 PM

You wouldn't technically lose any top speed, even a signifacantly mod'd f-body can't max out top gear, so you just bring the max into a more attainable zone with gears. I have a program that will calculate your current and new top speeds if you want, just pm me your what your current gears are and your tire size, along with those and the A4 info i already know I can tell you the old and new max speeds allowable by redline in 4th

**oneBADDz** · 12-04-2005, 04:42 PM

Actually I say you can't reach the top of 4th, I guess it depends what gears you have now, I had an M6 with 2.73s ( i know i know don't make fun I was gettin milage like you would never imagine) and I ran out of speedo before I ran out of 5th gear, who knows what 6th would have got me to if I had the power

**GatorSS** · 12-04-2005, 07:36 PM

Did you install the 2.73 gear in your M6? You surely must have gotten some killer mileage with that...like 35 MPG or more highway. With my M6 and stock 3.42 gear, I get 30-32 MPG highway (depending on weather conditions).

**oneBADDz** · 12-04-2005, 07:58 PM

I was getting right around 34, it was bogging down on almost any significant hill. I don't remember exactly what rpm it was running at 70 and I don't want to lie to you but I think it was about 1400-1500. I never had it with the 3.42s, the guy I bought it from liked to screw around with the cars before he sold them so he switched my 3.42s with an automatic and my car got the 2.73s before I ever owned it.