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This is quite a story..... I have read so many posts about how C5''s with an M6 benefit from gears. I did a bunch of research and decided on 3.90's. Got the differential swapped a few weeks ago and finally got the gears broke in. After the gears were broke in, I finally had my chance to let er rip. I thought this doesn't really feel any different? Couldn't really feel any difference?
So for what ever reason I decided to take a look at the rear differential that was taken out and much to my surprise.... I had 3.73 gears in it! Good God man you have got to be kidding me, lol. I thought all C5' with an M6 had 3.43's? I am not sure what the value of the differential is? I can tell you it is absolutely mint and had just over 18,000 miles when removed a few weeks ago. Any ideas? Thanks guys
I've been looking as I want to upgrade mine and I don't think I've ever seen a good rear unit go for less than $600. Some people want stupid money (stupid in my opinion for a used rear).
Where are you located?
Edit: I'll assume this is a single rib diff as you mentioned having an M6 and not an M12? The 3 rib version sells for a bit more...
3.73s are great for an A4. A4 cars came with a 2.73, or an optional 3.15. But I agree, there's not going to be a huge difference going from a 3.42 to a 3.73 in a 6spd manual. Hate to say it, but you probably should've inspected the diff as soon as you got it, NOT after it was installed. Sadly, in modern society, it pays to not trust most people, and distrust the rest....
Last edited by grinder11; Apr 5, 2023 at 11:49 AM.
3.73s are great for an A4. A4 cars came with a 2.73, or an optional 3.15. But I agree, there's not going to be a huge difference going from a 3.42 to a 3.73 in a 6spd manual. Hate to say it, but you probably should've inspected the diff as soon as you got it, NOT after it was installed. Sadly, in modern society, it pays to not trust most people, and distrust the rest....
Hey grinder, he's referring to his first diff which was in the car already that was also a 3.73. He bought a new diff to switch in a 3.90 but after driving and upon further inspection his car already had a 3.73 swap. Which he was unaware of.
Yeah 3.42 to 3.73 not a big difference. Same going from 3.73 to 3.90.
OP- On the bright side you have a backup handy. I've blown two 4.10 diffs and ended up back in my 3 rib 3.42 that I had pulled out years ago. It was very convenient having a that diff handy when mine broke.
Alright i need to do a little clarification, lol. From all the research I have done all C5's with M6's came with 3.42 gears. So I assumed I had 3.42' in my car with the factory differential. So I bought a built differential with 3.90 gears. Broke the gears for about 2 weeks. After the brake in I finally got to rip on it a bit. To my surprise it didn't feel much different. Decided to look over my factory differential and it is stamped and labled 3.73. So essentially I went from 3.73 to 3.90.
The point of this post is I am not aware of a factory GETRAG C5 differential with 3.73 gears. You could build a differential with 3.73's. But this looks to be factory? Hope this makes sense
Are you the original owner of the car? If not, I HIGHLY suspect the previous owner added the 3.73. Your research is correct. ALL M6 cars came from the factory with 3.42s.
I am not the original owner. I inherited the car, so I would be the 3rd owner. All this differential stuff got me digging through files to find out more about the car. When digging I found a little piece of paper that I had never found before when going through the car files. I have been through those files no less than 20 times. The car was purchased new from Purifoy Chevrolet in Granby Colorado with 800 miles on it. The dealership apparently had the car customized! The car built by DRM (Doug Rippie Motorsports). The car has a DRM 510, which would have been a 383 stroker with ported polished heads, cam, ported TB, ported intake, 1 5/8 headers, GTX exhaust and apparently 3.73 differential? The dealership added HRE wheels, stripes and a carbon fiber package.
Original sticker was $48,000 with all the upgrades the car sold for $66,950 back in 2000. That was a chunk of change back then, lol. If I would have known what I had I would have left it alone 😔. I have done headers, ported fast 92, ported LS2, cam, 1 7/8 headers.
Car originally dynoed at 417/ 418 to the wheels. now we're at 492/458 to the wheels. Like i said if I'd have know, lol.
Alright i need to do a little clarification, lol. From all the research I have done all C5's with M6's came with 3.42 gears. So I assumed I had 3.42' in my car with the factory differential. So I bought a built differential with 3.90 gears. Broke the gears for about 2 weeks. After the brake in I finally got to rip on it a bit. To my surprise it didn't feel much different. Decided to look over my factory differential and it is stamped and labled 3.73. So essentially I went from 3.73 to 3.90.
The point of this post is I am not aware of a factory GETRAG C5 differential with 3.73 gears. You could build a differential with 3.73's. But this looks to be factory? Hope this makes sense
3.42 is the only factory option in manual C5s. Factory diff never came in anything but 3.42 on any manual variant of the C5. Including the Z06.
Your diff was swapped.
Last edited by Johnny Hardcore; Apr 5, 2023 at 01:11 PM.
PS...many who just have a gear swap done (within the factory diff) will have gears that don't match the tag/lable on the diff.
Yours with 3.73 is an aftermarket diff with the 3.73 tag. Aftermarket as in factory diff case with aftermarket guts. And an aftermarket tag on the outside.
Last edited by Johnny Hardcore; Apr 5, 2023 at 01:13 PM.
I am not the original owner. I inherited the car, so I would be the 3rd owner. All this differential stuff got me digging through files to find out more about the car. When digging I found a little piece of paper that I had never found before when going through the car files. I have been through those files no less than 20 times. The car was purchased new from Purifoy Chevrolet in Granby Colorado with 800 miles on it. The dealership apparently had the car customized! The car built by DRM (Doug Ripple Motorsports). The car has a DRM 510, which would have been a 383 stroker with ported polished heads, cam, ported TB, ported intake, 1 5/8 headers, GTX exhaust and apparently 3.73 differential? The dealership added HRE wheels, stripes and a carbon fiber package.
Original sticker was $48,000 with all the upgrades the car sold for $66,950 back in 2000. That was a chunk of change back then, lol. If I would have known what I had I would have left it alone 😔. I have done headers, ported fast 92, ported LS2, cam, 1 7/8 headers.
Car originally dynoed at 417/ 418 to the wheels. now we're at 492/458 to the wheels. Like i said if I'd have know, lol.
Wow! Yeah, it seems like you've spent a good deal of money making some very small upgrades. I hope you kept all the old parts.
Wow! Yeah, it seems like you've spent a good deal of money making some very small upgrades. I hope you kept all the old parts.
I feel absolutely sick about it! I do have all the old parts! I might just throw it back together the way it used to be? Not sure what to do at this point!
I've never heard of nor seen anyone on this forum mention a factory Getrag 3.73 C5 differential. So maybe this was a GM over the counter performance part from back in the day?
I highly doubt Doug Rippie Motorsports had custom Getrag metal tags made.
They are still in business, correct? Call them up and ask.
I'd say it's a pretty rare part.
3 ribs are more desirable for guys making big HP.
I've never heard of nor seen anyone on this forum mention a factory Getrag 3.73 C5 differential. So maybe this was a GM over the counter performance part from back in the day?
I highly doubt Doug Rippie Motorsports had custom Getrag metal tags made.
They are still in business, correct? Call them up and ask.
I'd say it's a pretty rare part.
3 ribs are more desirable for guys making big HP.
Ron
Trying to multitask on a conference call. And poorly I might add. The case is likely a factory case/core with new guts and a new tag. Just like all the other "aftermarket" diffs I've seen. RPM retags their cores as well.
I feel absolutely sick about it! I do have all the old parts! I might just throw it back together the way it used to be? Not sure what to do at this point!
Nah, don't sweat it. You kept the old parts and now 20 years later your car is an even better performer than what DRM put out initially. Hold onto the parts and if you decide to sell the car just move it with the take-offs.
Nah, don't sweat it. You kept the old parts and now 20 years later your car is an even better performer than what DRM put out initially. Hold onto the parts and if you decide to sell the car just move it with the take-offs.
Why feel bad? 75 extra horsepower would never make me feel bad. The DRM package is neat but I doubt it would make it some rare collectible. Enjoy what sounds like a nice fast ride
The odd thing about this is the sticker on the diff cover calls it out as a 3.73 also makes you wonder, it sure appears factory.
Tags can be made exactly like the OEM tags with very little trouble today, now that the computer age is here. We had a machine at my shop-And this was 7 years ago technology-that I guarantee could've made this tag, no problem. Just saying because it looks OEM doesnt mean anything as far as GM ever building this diff.
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GETRAG 3.73 FACTORY DIFFERENTIAL Value?
