I'm in the middle of doing a cam swap (cc503) plus headers for my 1994 LT1 Z28 A4. I have a stock converter along with 2.73's and I'm questioning getting a 3.42 rear end gear for more giddy up. My question is, Is there anything that can be used from the stock Differential unit? or is the only thing I have to do is change ring and pinion gear. would just like to know before I get a tune and speedometer adjusted for rear end gear. also a part number for which parts to buy would be great

 

You could just change the ring & pinion. But you need to address the difference in the "carrier". A 2.73 gear is mounted to a "2-series" carrier, a 3.42 gear from the factory is mounted to a "3-series" carrier. To avoid having to buy a new limited slip carrier, or a spacer ring, you need to buy a 3.42 ring & pinion that specifically fits in a 2-series carrier. Here's an example:

https://www.summitracing.com/parts/r...maro/year/1994

You should buy an install kit that includes the required replacement parts including the bearings.

Many people with the auto trans opt for 3.73 gears.

Are you planning to do this yourself? It requires specialized tools and can be a challenge.

 

I originally planned to do this myself. luckily for me I'm still in high school and we happen to have an automotive shop with an abundance of tools and a knowledgeable teacher that can help me out should I need it. My reason for not going higher than a 3.42 is because I still want to retain some highway mileage, I plan to daily this car. would be a different story if I had an M6. I will look for an install kit, thanks Injuneer

 

As 'Injuneer' stated, you would need a 3.42 gear set for a series 2 carrier, also referred to as a 'thick' set. And as also stated, 3.73s are the most popular upgrade for Auto trans.
As far as highway mileage, mpg isn't affected as much as you would think, what is more visually affected is RPM.
Based upon many thread responses here and on other forums, you're probably getting 25.5mpg highway. 3.42s' would drop that to 24 and 3.73s' to 23 1/4.
Even though I'm 98 LS1, my 3.23s' gave 24.5 and the 4.56s' gave 21.5.

A better bang for the buck would be an aftermarket performance torque converter, and not something in the 2500-3200 range, a decent one in the 3500-4000 range.

 

I know my gas mileage will not be that high since i'm going to be running a larger cam when my engine is back together. and RPM's do matter for me, for example i don't want to be doing more than 2500 rpm at 80 mph in overdrive which is what i do in my 95 K2500 truck that also has 3.42 gear. with 3.42s i think the rpm would actually be higher than my truck's because my truck has taller tires compared to my Z, correct me if I'm wrong

 

I do think with the 3.42s' and the converter locked cruising at 80 your rpm will be 2500.
With my 4.56s' and the converter locked my rpm at 60 is 2500, 3000 at 72, 3300 at 80. Speedometer I don't trust so I use a GPS unit to show true mph and my tach is 150rpm off so I use a ScanGaugeII to show true rpm.

 

then i think I'll stick with the 3.42's. I am saving up for a good converter, them yanks are pretty expensive, but I would like to swap an M6 in there maybe one day. as a teenager I don't have a lot of money for a lot of the stuff I want

 

A good converter is gonna be about $800. You buy a less expensive converter ($400) and you would never be satisfied, too much slippage (looseness) and inefficient at top end. Then you'd do it all over again to get a good one, wasting that $400,time,labor.
Yes, M6s' are fun but that's all. You go 3.42s' with a good converter and you'd stop thinking M6 as an M6 wouldn't be able to hang with you.

 

I know manuals will always be slower than auto's but i'd just love to have a manual car. if I got an M6 one day then I know 3.42's simply wont be enough. but until then i'll be saving for a good converter and 2 series carrier 3.42. I appreciate your guys' useful info

 

also, I think you can adjust the speedo for gears by having someone mess with the tune, if you're interested anyways

 

He might be a little higher. 3.23’s and the converter locked with stock sized tires. My speedometer is spot on,

65mph is 2200 rpm.

 

exactly what I was thinking, since the truck stock tires are taller than the stock camaro tires they help bring the rpms down just a tad with TCC locked