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Discussion Starter #1
My corvette left the factory in 2000 with a 2.73:1 differential mated to the 4l60e transmission. When I got the car someone had swapped in a 3.90 gear had the transmission built by rpm transmission and I think they put a converter in it because it feels like it slips a little at low rpms but only until you open the throttle. I put an LSX376 engine in it and a used 2.73 gear diff purchased off of ebay and I filled it with royal purple. This diff has been incredible. car has good power and gets surprising mileage for being a 6.2L 450hp 433tq beast. But the diff leaks. It is wet And the rear spring under it is completely saturated in it's oil.

Because I am replacing the springs with hyperco upgrades, I must deal with these leaks. And honestly I feel if I am not gonna boost my LSX this year then I have cut myself short with that 2.73 gear. Because of my experience with the 3.90 I don't want to even try the z06 3.42 diff. So I ordered me up a new 3.15 diff. I won't brag but you would not believe what I found this thing for. brand new. guaranteed not to leak and it's a good match to the crate motor.
 

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My corvette left the factory in 2000 with a 2.73:1 differential mated to the 4l60e transmission. When I got the car someone had swapped in a 3.90 gear had the transmission built by rpm transmission and I think they put a converter in it because it feels like it slips a little at low rpms but only until you open the throttle. I put an LSX376 engine in it and a used 2.73 gear diff purchased off of ebay and I filled it with royal purple. This diff has been incredible. car has good power and gets surprising mileage for being a 6.2L 450hp 433tq beast. But the diff leaks. It is wet And the rear spring under it is completely saturated in it's oil.

Because I am replacing the springs with hyperco upgrades, I must deal with these leaks. And honestly I feel if I am not gonna boost my LSX this year then I have cut myself short with that 2.73 gear. Because of my experience with the 3.90 I don't want to even try the z06 3.42 diff. So I ordered me up a new 3.15 diff. I won't brag but you would not believe what I found this thing for. brand new. guaranteed not to leak and it's a good match to the crate motor.
IMO you should have had me build you a 3 rib with all C6 Z06 internals....would probably have been cheaper
 

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Discussion Starter #3
What is the diff between z06 3 rib 3.42 diff and the 3 rib 3.15 diff I am buying and my 2.73 gear diff. the cases look the same from the outside. Aside from gear ratio what is different in the z06 differential?
 

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the cases are the same other than the speed sensor is moved off center of a rib. This requires the use of an extra thick ring gear which really limits your choices in gear selection. Which case you use doesn't really matter as long as it is a 3 rib case.

Using a 3 rib diff (either auto or manual) you retain the case and carrier. You put in which ever aftermarket (or stock) gear you want, then full it with the following C6 Z06 diff parts:

- pinion carrier
- left/right output shafts
- left spider gear
- carrier clutches disc, steels, and clutch springs

Top it off with all new snap rings, seals, and o-rings and an ECS trans/diff brace and either solid or poly diff and engine mounts. You now have a diff good for over 800 hp.
 

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Discussion Starter #5
Well now I have a good leaky 2.73 diff core to have built at a later date. I threw the 3.90 diff in the garbage back when I changed it because from the time it was technically broken and making noise, I had to keep driving it for a few months until I could fix it. Upon seeing the following I made the assessment that I had an unrebuildable core..





But that is not what I am up against this time. The diff I am removing is quiet and works awesome just a few leaks. Its just not cool for me to tear my car down at work and tie up a rack for any given day. So when I go to work on my car in the shop, it needs to be fast r&r.
 

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you don't still happen to have that busted 3.90 do you? I may be interested for a spare for Drag Week
 

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Discussion Starter #7
naa. I threw it away when I swapped it. I understood the color of that fluid indicated the diff was munching the aluminum housing. or at least I thought and never tore down to inspect
 

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the carrier itself is mostly aluminum as well as the pinion support.
 

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Discussion Starter #9
Oh man. It came. And it really is new. I mean, Wow. This won't leak on my new spring..


 

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Discussion Starter #10
I want to briefly discuss why I have elected to change the diff..


I like to fill the diff through this hole before assembly to the transmission vs. dealing with the fill plug hole..


So now I am new on both ends of the driveline..




So I got all the right parts, now. LSX376, 3.15 gears, 19"&18" wheels, and the a4 trans built by rpm..


Gotta spend a few weekends with my car on the dyno and just dial all this in to perfection. It runs pretty darn good right now, but with a dyno and the ability to look at an actual power curve brings the ability to fine tune shift points to keep my engine in its powerband.
 

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Discussion Starter #11
Oh man, Has it been a while since I updated this thread. Well here is my car today..



I have had this machine to the drag strip at PBIR many times, now and this car is consistently worth [email protected] in the 1/4 mile. From the time of my last post I traded the built RPM trans that I thought was bad with the 3500 stall converter for a rebuilt stock 4l60E from Jasper with stock converter. I now have a RPM lvl 6 4l60E with 2500 stall converter. And have been to the track so many times that I now have permanent numbers on my car..





And I have ordered a Z06 diff from Ebay. This will change my gear ratio from 3.15 to 3.42. I can't wait to find out what this is worth going down the 1320.
 

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With your engine, that gear change should improve your 0-60 0-100 feet time and maybe good for a tenth or two at the 1320
 

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Discussion Starter #13
I can't wait to find out. I am also going to swap cams. I have a cam out of a LS3/480 and a fuel system upgrade already in my possession. I have been so consistent at [email protected] I must have 12 or 15 timeslips like this. If I grip and I make a good run I am getting up to 110mph and it is gonna take me 12.6 seconds to get there. I am going to spend time with this on the dyno and tell myself I am gonna break into the 11's. My timetable right now is first shipping on the diff, and then whenever the local track(PBIR) reopens. I will swap the diff and upgrade the fuel supply on one weekend and change the cam on the next. These things will not hold me back and I am afraid in the end I will be waiting for the track to reopen. But I am set to have a lot of fun this summer. I will make some hq youtube videos of me changing these parts alone at the shop in the next few weeks.
 

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Discussion Starter #14
Oh yes! YES!! It came. My used ebay 69k mile Z06 3.42:1 diff has arrived. And not strapped down to a pallet. But w/e..



It came on a ups truck inside a cardboard box packed with a bunch of cardboard. The box was oil soaked in places. But outside of the plastic everything looks good..





And here is what really matters..





This is going behind a RPM level 6 4l60e with a 2500 stall converter from FTC. Oh happy days are ahead for me this summer. I will install this at work this weekend.
 

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Discussion Starter #15
It has been a busy weekend and I finally got to get started on my project..



I am doing all of this during tropical storm Arthur. So after the car finished dripping and the floor was dried I got the rear suspension out of the vehicle and hung from one of the rack arms..





That diff and trans are really clean, right? I have to find someone to sell this diff to. It was brand new when I got it, has 20k miles on it and has only seen royal purple fluid. And after draining that fluid and unbolting the 4 support rods and the bolts holding the diff to the trans, the old, slow 3.15 gear slides right off the back of the RPM 4l60E..



The new diff installed looks a whole lot like the old diff..



And I filled it with the royal purple..

 
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