373 Gears?

[racZ28]

I'm thinking about installing 373 gears in my rear end. Does any one have them already? If so, what kind of changes will I see in acceleration and rpm's at highway speeds?

[pajeff02]

I run 3.73's in our car. The general rule of thumb is A4 cars should upgrade to 3.73's and M6 cars to 4.10's. I honestly cannot tell you what RPM our car runs at down the highway, but it isn't bad at all. Stock tire height is something like 25.6" and you can either math it out or go to an on-line converter that will tell you the RPM.

[SteveC]

I have 3.73:1 gears in my 01 Z28 (Sara) and the rpm difference from the stock 3.23:1 (GU5) was 500. I did not notice that much of a difference in the pickup until I had a Y3000 stall (should have gone to 3600) Yank converter installed

SteveC

[pajeff02]

I went with a 3,200 stall -- also should have jumped up to the 3,600. Live and learn.

[cpop98ws6]

I have a Yank SS 3,600 stall and 4:10 gears. On the highway doing 70 MPH the RPM's are at 2,500. I am very happy with my gear choice!

[2002ssslp]

I would go with the 4.10's over the 3.73's because of the overdrives in both the M6 and A4 cars. I am waiting to break my 10 bolt so I can get a 4.10 9" from Strange.

[pajeff02]

I considered something steeper than 3.73's, but have no complaints. As cpop posted, he went with them in his car and they appear to also work great with an A4. Hell, he might even be able to edge by me at the track... at about the 100' mark and then all I see is his tail lights!

[SS Camaro UK]

The general rule of thumb is A4 cars should upgrade to 3.73's and M6 cars to 4.10's.

I've also read this quite alot, is there a particular reason for this?

Out of interest, has anyone used 4.10's with an A4?

[cpop98ws6]

I am. Read post #5, I'm very happy with 4:10s and a A4. Lots of fun on the street and not to bad on gas on the highway.

[Firebirdjones]

I've also read this quite alot, is there a particular reason for this?

Out of interest, has anyone used 4.10's with an A4?

I use 4.10's with an A3, does that count?

I think the reason you read it quite a lot may be due to this generation of people that have gotten attached to their overdrives, and aren't used to buzzing the engine down the highway. Honestly though, I think the 3.73 or the 4.10 with an A4 is a good combination that still has excellent highway manors and good acceleration at the same time.
I personally wouldn't even squabble at any gear with an overdrive tranny in front. But if you drive quite a bit and don't frequent the track so much, and like loafing down the highway at high speeds, maybe steeper gears aren't a good idea.

Like Jeff said, decide what you might be comfortable with as far as rpm cruising goes.

[SS Camaro UK]

It's good to know that.

Is the car's top speed affected as well?

[Firebirdjones]

Don't know. How fast do you want it to go? These 4L60's will shift into overdrive at full throttle, with that said, I would think they would still go as fast as you care to go.

[Firebirdjones]

Here you go, play with this. You can change the gear ratios, transmission ratios, tire height, etc...I've found it to be accurate with my stuff.



RPM / Speed / Gear Ratio Visual Calc

[Firebirdjones]

I ran a test for you,,,,

With 3.73's, shifting into overdrive (.70 ratio with automatic) at full throttle and only running it to 4800 rpms with a stock 26" tire you'll be going 140 mph and there is still room to spare. I'd say that's fast enough (I know I'll never do it anyway)

[SS Camaro UK]

I was just being curious. I wouldn't risk my car being totalled, not after waiting for so long for it.

[kingls1]

I run 3.73's in our car. The general rule of thumb is A4 cars should upgrade to 3.73's and M6 cars to 4.10's. I honestly cannot tell you what RPM our car runs at down the highway, but it isn't bad at all. Stock tire height is something like 25.6" and you can either math it out or go to an on-line converter that will tell you the RPM.

How do you go about finding out what the gear ratio is without dropping the cover? I have a six speed & at 70mph in sixth it tacks 1600 all day long hills and all, it will do 85 in 3rd near redline

[Firebirdjones]

all 6 speeds got 3.42's. 70 mph at 1600 sounds right on the button for 3.42's.

[JacobLS1]

3.73, A4, i get 3000rpms at 75mph. still get 25mpgs/hwy though.

[pajeff02]

How do you go about finding out what the gear ratio is without dropping the cover? I have a six speed & at 70mph in sixth it tacks 1600 all day long hills and all, it will do 85 in 3rd near redline

FBJ posted an answer... but if you ever need to verify a rear end ratio it is easy to do. Block the front wheels and support your rear axle on jackstands. Place the transmission in neutral and then make a mark on both the driveshaft and nose of the differential that line up with one another. Also place a mark on the inside of your tire that you can easily see and that points straight down. Now, simply rotate the driveshaft as many times as it takes to turn the tire one complete revolution, counting the turns of the driveshaft as you go. A 3.42 ratio rear will require you to turn the driveshaft just under 3-1/2 times to get one full tire revolution as the number of turns corresponds exactly with the ratio.

[kingls1]

FBJ posted an answer... but if you ever need to verify a rear end ratio it is easy to do. Block the front wheels and support your rear axle on jackstands. Place the transmission in neutral and then make a mark on both the driveshaft and nose of the differential that line up with one another. Also place a mark on the inside of your tire that you can easily see and that points straight down. Now, simply rotate the driveshaft as many times as it takes to turn the tire one complete revolution, counting the turns of the driveshaft as you go. A 3.42 ratio rear will require you to turn the driveshaft just under 3-1/2 times to get one full tire revolution as the number of turns corresponds exactly with the ratio.

that sounds easy enough, I'll give it a try