Gear ratio

[Screaming mad]

Ive got a 3.4l v6 maro with a 4l60e, which is currently been fully rebuilt again, does any one know what diff gears came on these 3.4l rear ends? Been told To upgrade to a rear z28 end, but i would like to know the ratio's and other avaiable after market ratio's so I can come up with the best option. I want to achive faster 0-60, so iI need lower ratio?
Z28 is 3.42:1?
What is 3.4l v6 ratio?
What other gears can I buy?
Will I loose top end speed or acceleration from changing to z28 rear?

Cheers guy and girls

[78formula78]

well i can't tell you exactly what gears your 3.4 has in it now i can tell you that swiching the gears will effect your top end such as if you had a 2.76 your going to have a huge top in in camparison to a 4.10 rear end but the 4.10 will blow the 2.76 away in 0-60 and 1/4 mile but the 2.76 will win the top end. but unless you go with any really high gears like anything above a 4.10 your not gonna noticed the loss in top end (unless you drive at over 120 mph on a regular basis)

[Injuneer]

I think the 3.4L's have a 3.08:1 rear axle ratio - but not sure. You can check by looking at the build tag, showing all the options and features of your car. Could be on the edge of the driver's door, in the console or in the glove box. It will have a bunch of 3-letter/number RPO codes. The rear axle ratio would be indicated by:

GU2 = 2.73 (V8 A4 without "performance rear axle)
GU4 = 3.08
GU5 = 3.23 (V8 A4 with "performance rear axle)
GU6 = 3.42 (V8 with M6 - all)

(There are exceptions in 1993, where the V8 M6's came with either 2.73 or 3.23 rear axles. All other 4th Gens, from 1994 - 2002 will be per the chart, above.)

The presence of G80 would indicate you have a limited slip differential (standard on V8's, optional on the V6's).

Think of the rear axle ratio as a "torque multiplier". If you go from a 3.08 to a 3.42, it will feel like you added 11% more torque to your engine. You will also run out of RPM at a lower MPH, though.

Your best bet would be to find a complete rear axle assembly from a V8 Camaro or Firebird with a 6-speed manual. That would get you a rear axle assembly with 1) 3.42 gears, 2) limited slip differential, and 3) disc rear brakes. Of course if your V6 already has the optional limited slip (G80) and disc brakes (J65) you would only need to get a new set of gear and an install kit.

You could also consider moving up to a 3.73 or 4.10 ratio, but those will be a problem without a limited slip, and may reduce your fuel mileage a bit.

[Screaming mad]

Thanks for that info guys... before i start the big search what do i need to do about the engine computer and speedo. obviously they will get faulse readings.. is there lots of different speed sensors? adjustable speed sensor?

[Injuneer]

The speedometer is adjusted for rear axle ratio by programming the gear ratio into the PCM. Not sure of the avaialbility of programmers (like the Hypertech) for the V6, or whether there are mail order "tuners" who will make the adjustment for you.

[78formula78]

im not a hundred precent positive but i do belive all you need to do is reprogram the computer and have it set to your new ratio, i know the little handled programers that you see advertised on tv all the time can usually set that kind of stuff, or at least it did in my dads truck, then as long as you got a the ratios correct and didn't mix up numbers then your speedo will be correct

[Screaming mad]

Well its time for a big search then, hand held programmer, and a rear axle, lsd, disk brakes, rear z28 suspension.. Just gotta find axle with one abs pickup though, then should fit straight on!
thanks guys!
I'll try get right axle, then play around with the gears, trial and error i guess!
I'll make this v6 move eventually!

[Screaming mad]

I think the 3.4L's have a 3.08:1 rear axle ratio - but not sure. You can check by looking at the build tag, showing all the options and features of your car. Could be on the edge of the driver's door, in the console or in the glove box. It will have a bunch of 3-letter/number RPO codes. The rear axle ratio would be indicated by:

GU2 = 2.73 (V8 A4 without "performance rear axle)
GU4 = 3.08
GU5 = 3.23 (V8 A4 with "performance rear axle)
GU6 = 3.42 (V8 with M6 - all)

(There are exceptions in 1993, where the V8 M6's came with either 2.73 or 3.23 rear axles. All other 4th Gens, from 1994 - 2002 will be per the chart, above.)

The presence of G80 would indicate you have a limited slip differential (standard on V8's, optional on the V6's).

Think of the rear axle ratio as a "torque multiplier". If you go from a 3.08 to a 3.42, it will feel like you added 11% more torque to your engine. You will also run out of RPM at a lower MPH, though.

Your best bet would be to find a complete rear axle assembly from a V8 Camaro or Firebird with a 6-speed manual. That would get you a rear axle assembly with 1) 3.42 gears, 2) limited slip differential, and 3) disc rear brakes. Of course if your V6 already has the optional limited slip (G80) and disc brakes (J65) you would only need to get a new set of gear and an install kit.

You could also consider moving up to a 3.73 or 4.10 ratio, but those will be a problem without a limited slip, and may reduce your fuel mileage a bit.

Well I've found the code, it's a GU5 that makes it a 3.23 according to your table..

so my option is 3.42 with lsd and disk brakes, I guess then I can buy 3.73 and 4.10 gears and try them out? Is it this easy?

I dont have any interest in top speed really (As already in trouble for doing 101mph!) but dont want rev's to be too high at 60-70mph, still want some economy!

70mph is at...

2000rpm 3.23gears
2150 3.42
2350 3.73
2600 4.10

my thoughts is to get the 3.73 gears as I believe its the best all round option? What do you guys think?

Cheers guys!

[Joe 1320]

The 3.4s came with 3.23 gears, rear drum brakes and a two piece driveshaft. The ideal gear is a 3.42 from a 94-97 Z28 or TransAm. This rear swap will give you the 3.42s and rear disks. Be sure to swap driveshafts too. 3.73s are a little too steep to be of benefit, you are shifting thought the lower gears too quick..... you can't take advantage of the engine's torque and it doesn't produce enough upper rpm power for the gears to really work. Your biggest problem is the speedo correction. Your easist solution is one of two things: Either have someone flash a new program to correct the speedo or get a calibration box. There is no hand held quick fix programmer for the 3.4s.

[Screaming mad]

Thanks joe, gionna spend the day on the phone tomorrow tryin to sort things out!