Top Speed with 3.73's

[blackfire93]

What should my top speed with 3.73's and an A4 be? My car gets to about 115 and then it starts bouncing off the rev limiter at 6,000 RPM's. Why won't it shift into 4th? Is 4th gear like an overdrive for the auto?

[Z Ya Later]

What should my top speed with 3.73's and an A4 be? My car gets to about 115 and then it starts bouncing off the rev limiter at 6,000 RPM's. Why won't it shift into 4th? Is 4th gear like an overdrive for the auto?

What gears did your car have originally?

[DJ Taso]

What should my top speed with 3.73's and an A4 be? My car gets to about 115 and then it starts bouncing off the rev limiter at 6,000 RPM's. Why won't it shift into 4th? Is 4th gear like an overdrive for the auto?

115?? There's something definetely wrong.

[KnightFire]

Sounds like your car didn't originally come with Z rated tires and performance axle package and your hitting the speed limiter. Easily programmed out with a chip from pcmforless.com

How far up does your speedo go? Do you know the original packaging?


KnightFire

[smokin2001Formula]

I agree with the last post it sounds like you have definetely hit the the governed speed limit set. That can easily be changed with a handheld programming device.

[Joe 1320]

Sounds like your car didn't originally come with Z rated tires and performance axle package and your hitting the speed limiter.

Bingo, that's exactly what I was thinking. My bet is that if you let the car accelerate mildly, get up to highway speed, let it stay in 4th and gradually push the speed up, you'll find that it still will top out at the same speed.

[Injuneer]

I agree with the last post it sounds like you have definetely hit the the governed speed limit set. That can easily be changed with a handheld programming device.

93 was last year with a removable "chip"... he needs a new one burned to alter anything like the speed limiter.

With 3.73's on a 4L60, and stock tire height, you should be at about 3,920RPM at 115MPH in overdrive. A 5,900rpm redline would put you at 170mph, but it isn't going to go that fast because of the aero drag exceeding the force available at the rear wheels.

The 4L60 4th gear is an 0.696:1 overdrive.

[jerrysta]

I had the same problem. It was absolutely related to the computer.

However, in my case after that was solved I found out I need to get a new driveshaft, too, thanks to all the vibrations at high speed. Hope yours is a little better balanced from the factory than mine was.

I still haven't replaced it, although how often do you drive 90-100 mph. Not too often in my case.

[blackfire93]

My car originally came with the 3.23 gears. The speedometer goes to 155 mph. I've also had it at 135 to 140 before I put the gears and madz28 chip in it.

[xxRillixx]

Mine hits the regulater and loses power at 115 in OD also... shift it into D and youll get it up to 135-140 after that it doesnt increase much but you dont max out on the RPM's... i think its at like 4,000? 4,500? Been a while since ive had that much open road.

Im thinking of doing the same thing... what would my rpm's be at on the highway (between 75-85).

[Z Ya Later]

Mine hits the regulater and loses power at 115 in OD also... shift it into D and youll get it up to 135-140 after that it doesnt increase much but you dont max out on the RPM's... i think its at like 4,000? 4,500? Been a while since ive had that much open road.

Im thinking of doing the same thing... what would my rpm's be at on the highway (between 75-85).

In OD, you'll be looking at 2600-2800 for 75-85, roughly.

[xxRillixx]

In OD, you'll be looking at 2600-2800 for 75-85, roughly.

That sounds low :shrug: ... what about 4.11's?

[redbird94]

if you had it at the speed before the gears then your speedometer is off and you need to get your computer reprogrammed go to pcmforless.com they do a great job, its cheap, and you are supposed to pick up 15-20 horse if you run 93 octane, he can change shift points, fan temps, everything.

[Injuneer]

My car originally came with the 3.23 gears. The speedometer goes to 155 mph. I've also had it at 135 to 140 before I put the gears and madz28 chip in it.

if you had it at the speed before the gears then your speedometer is off and you need to get your computer reprogrammed go to pcmforless.com

No!

blackfire's car, because it has the 3.23 gears from the factory, and does not have a speed limiter (well, it does sort of, because the limit of the 8-bit binary field in the factory program is "255"). He could easilly have gone 137mph in 3rd gear, because that's exactly what the speed works out to with 3.23's and using 1.00:1 3rd gear. Only the cars with 2.73 gears (and 110mph speedos, and no ability to select 1st gear) came with the speed limiter of approx 115mph (exact limit varies with year of the car).

Here's a table of rpm vs. mph for the 4L60/4L60E in 3rd anf 4th (O/D) gears:

Axle: - 2.73 - - - 2.73 - - - 3.23 - - - 3.23 - - - 3.73 - - - 3.73 - - - 4.10 - - - 4.10

gear-> -3 - - - - - 4 - - - - - 3 - - - - - 4 - - - - -3 - - - - -4 - - - - - 3 - - - - - 4
MPH - - - - - - - - - - - - - - - - - - - - - RPM
60 - - 2,147 - - 1,495 - - - 2,540 - - 1,769 - - - 2,933 - - 2,043 - - - 3,224 - - 2,245

70 - - 2,505 - - 1,744 - - - 2,964 - - 2,063 - - - 3,423 - - 2,383 - - - 3,762 - - 2,619

80 - -2,863 - - 1,993 - - - 3,387 - - 2,358 - - - 3,912 - - 2,723 - - -4,300 - - 2,993

90 - - 3,221 - - 2,242 - - - 3,811 - - 2,653 - - - 4,401 - - 3,063 - - - 4,837 - - 3,367

100 - 3,579 - - 2,491 - - - 4,234 - - 2,947 - - - 4,890 - - 3,403 - - - 5,375 - - 3,741

At rev limit:

RPM MPH
5800 - 162 - - - - 233 - - - 137 - - - - 197 - - - 119 - - - - 170 - - - 108 - - - 155

[Z Ya Later]

That sounds low :shrug: ... what about 4.11's?

2800-3200.

Here's a good calculator that I use.

http://www.f-body.org/gears/