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Do the c5 manual 3.42 gear diffs from stock c5s bolt directly up in place on the auto trans c5s? Just curious these autos really could use some better gearing and the 3.42s can be found on ebay for a fair price. I read somewhere they had something different on the front plate to where you had to use an auto diff. Yukon i think it was stated there gears sets didn't fit the 2.73 housing but did work on the 3.15 and up rear diffs. I was quoted 900$ for gear, labor and seals from a reputable from 3.42s-3.73s and 4.10s.
Referring to the 2.73 vs 3.xx gears. When it comes to rear gears, there are different size carriers for each series of gears. So a 2 series carrier normally holds 2.73 gears and really any other 2.xx gears and a 3 series carrier holds 3 series gears. You can, however, often find (but not in every gear size and not always) special gears made to fit in the other carrier. Meaning there are 3.xxx gears that can fit in a 2 series carrier and 2.xxx gears that can fit in a 3 series carrier. Again, not always easy to find and not everyone likes to use them, because they are a little different and sometimes (depending) not as strong. And, I presume since the Corvette dif is just not a widely used carrier, it's harder to find anything that fits under that scheme. For example, in my other car, I currently have very tall 2.73 gear in my 3 series carrier, and it still required a little bit of grinding of the carrier to get it to fit at all.
In addition, specifically to the corvette, you often don't want to run a 2 series carrier anyway if you decide to do certain type of racing as the 2 series is almost always a 1 rib design, which is believed to be much weaker than a 3 rib design so make sure you check if you are going to do anything hard on the car.
Referring to the 2.73 vs 3.xx gears. When it comes to rear gears, there are different size carriers for each series of gears. So a 2 series carrier normally holds 2.73 gears and really any other 2.xx gears and a 3 series carrier holds 3 series gears. You can, however, often find (but not in every gear size and not always) special gears made to fit in the other carrier. Meaning there are 3.xxx gears that can fit in a 2 series carrier and 2.xxx gears that can fit in a 3 series carrier. Again, not always easy to find and not everyone likes to use them, because they are a little different and sometimes (depending) not as strong. And, I presume since the Corvette dif is just not a widely used carrier, it's harder to find anything that fits under that scheme. For example, in my other car, I currently have very tall 2.73 gear in my 3 series carrier, and it still required a little bit of grinding of the carrier to get it to fit at all.
In addition, specifically to the corvette, you often don't want to run a 2 series carrier anyway if you decide to do certain type of racing as the 2 series is almost always a 1 rib design, which is believed to be much weaker than a 3 rib design so make sure you check if you are going to do anything hard on the car.
This is good news. Do you know if the stock performance axle package 3.15 factory gear has the same carrier as the 3.42? How are the 2.73s? The 3.15s run good on the highway but i still think a 3.42 would maybe be a better option considering 1:1 ratio. Depending how you use the car 4:10s even with a six speed will top out depending what you do on the street. I had 4:10s in a 6 speed lt1 that would run quick for any type of racing. Would be nice to have a set of 4:10s in the auto.
Last edited by Justin Raney; Nov 29, 2021 at 03:43 PM.
The autos have deeper much deeper first gear, but still would see a big benefit in 2nd and 3rd with lower than 3.42. If you’re going to make the swap 3.73 would get much better performance.
This is good news. Do you know if the stock performance axle package 3.15 factory gear has the same carrier as the 3.42? How are the 2.73s? The 3.15s run good on the highway but i still think a 3.42 would maybe be a better option considering 1:1 ratio. Depending how you use the car 4:10s even with a six speed will top out depending what you do on the street. I had 4:10s in a 6 speed lt1 that would run quick for any type of racing. Would be nice to have a set of 4:10s in the auto.
To answer your question, YES, the 3.42 and 3.15 use the same 3 series carrier. I'm 99% certain the 3.73 would use the same carrier, too. Personally, I'd go with a 3.42 gear in an A4 C5. Mine came with a 3.15. Plus, if you ever go with a higher stall converter, the 3.42 makes the looser converter feel "tighter" than the 3.15 does. Going with the 3.42 gear, combined with the trannys 3.06 first gear, makes the car feel like a 350 turbo trans equipped car with a 4.20 rear end in first gear!! If you went with a 3.73 and the 3.06 first.......a 350 turbo trans would need a 4.60 (!!) gear to match. A 3.73 diff in a C5 A4 would need some mighty sticky tires to hook!!! A 3.73 or 3.90 would work great with a 6 speed manual C5. Just saying I'd go 3.42, or-maybe-a 3.73 at the most with a C5 A4.......
gear swap
