When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi today I'm looking at buying a new differential for my 1969 big block project, however when I found a differential with the right gear ratio (3.70 heavy duty) it ended up having a different case numbers. The seller says that it came from a 1969 corvette big block, which matches that date code on the top "C229" (see picture attached). However when you read the bottom stamping on the casing the first letters look to read "OH" . Which to my knowledge isn't a code used in 1969. I believe the right code for a 1969 corvette - 3.70 heavy duty gears was "FA". Any knowledge of why the stamping on the bottom doesn't match the top date code would be a great help. Thank you in advance.
Here is the bottom stamp of the differential that I believe to start with "OH"
Here is the top of the differential with the date code - C229 - which I believe to say March 22 1969 (if i'm reading that right)
sounds like you have some confusion about codes and diffs;
That is not a 1969 differential, it is a 1979, the housing casting is C229= March 22 1979. Who knows what it is inside. However if you are looking for a used differential to plug in and go you might be better off buying a lottery ticket.
I don't know who the seller is or where it is for sale but I have been doing this stuff a very long time and your comments are full of red flags.
First, I wouldn't consider any used or "rebuilt: diff unless you can see inside. If it was rebuilt how was it rebuilt? Some call replacing bearings a rebuild, maybe add in fiber clutches for extra money.
1969 was an extended year due to the strike, more 69's then 70's. Some 69 and all 70 housings were stamped with a 3 letter code prefix whereas previous and later diffs were stamped with 2 letter codes. No difference other then for those who want the correct date and stamping for an NCRS build.
The next myth I have see for years is calling a diff a BB HD one. What is the difference? stamping code, some posi cases were said to be shot peened but that didn't help if it was done since I have rebuilt plenty of 66-74 BB diff's that had cracked posi cases. The axles were called HD because they had cap and bolts to retain the u-joint vs the standard axle use U-bolts. DO NOT fall for this scam, there is very little difference in strength between them. I have seen u-joint break in half, axle ends wear down but never saw one fail yet because the u-bolt broke. The bearings, clutches, and all internal parts are the same between both SB and BB diff's.
1969 was the first year for the 2nd revision of the Eaton posi case. It was better than the previous Eaton and DANA posi cases but not by much. PLENTY of them failed. The design went through another revision in 1972. The spiders used in 69 were weaker 10/18 the clutches were the better solid steels.
1979 differentials were plagued by lousy QC and were the end of the line of the iron diff. They had better posi cases, better spiders, but lousy clutches, axles, and ring gear bolts. Assembly quality was terrible and plenty failed in warranty.
Again tying to find a "deal" with a low priced used diff is a gamble. Many are out of cars for issues they had. If you post pictures of this diff with the cover off I can tell you a lot more, if the seller won't pull the cover keep looking or learn how to correctly build these to last and one hint it is more involved than a few hours of labor and new bearings. If you want new gears that you will have to settle for imported ones since there are no more usa made gears that I am aware of.
Yea but the seller was going to use it in a 1969 small block corvette but it had the larger side yokes for the big block. I don't think they had the bigger side yokes in 1979.
No to my knowledge the side yokes for the 1969 corvette are different. Small blocks were smaller and the 427 big blocks were bigger with the "heavy duty" half shaft versions. And with the newer mid 70s cars they didn't make heavy duty versions just different ratios.
sounds like you have some confusion about codes and diffs;
That is not a 1969 differential, it is a 1979, the housing casting is C229= March 22 1979. Who knows what it is inside. However if you are looking for a used differential to plug in and go you might be better off buying a lottery ticket.
I don't know who the seller is or where it is for sale but I have been doing this stuff a very long time and your comments are full of red flags.
First, I wouldn't consider any used or "rebuilt: diff unless you can see inside. If it was rebuilt how was it rebuilt? Some call replacing bearings a rebuild, maybe add in fiber clutches for extra money.
1969 was an extended year due to the strike, more 69's then 70's. Some 69 and all 70 housings were stamped with a 3 letter code prefix whereas previous and later diffs were stamped with 2 letter codes. No difference other then for those who want the correct date and stamping for an NCRS build.
The next myth I have see for years is calling a diff a BB HD one. What is the difference? stamping code, some posi cases were said to be shot peened but that didn't help if it was done since I have rebuilt plenty of 66-74 BB diff's that had cracked posi cases. The axles were called HD because they had cap and bolts to retain the u-joint vs the standard axle use U-bolts. DO NOT fall for this scam, there is very little difference in strength between them. I have seen u-joint break in half, axle ends wear down but never saw one fail yet because the u-bolt broke. The bearings, clutches, and all internal parts are the same between both SB and BB diff's.
1969 was the first year for the 2nd revision of the Eaton posi case. It was better than the previous Eaton and DANA posi cases but not by much. PLENTY of them failed. The design went through another revision in 1972. The spiders used in 69 were weaker 10/18 the clutches were the better solid steels.
1979 differentials were plagued by lousy QC and were the end of the line of the iron diff. They had better posi cases, better spiders, but lousy clutches, axles, and ring gear bolts. Assembly quality was terrible and plenty failed in warranty.
Again tying to find a "deal" with a low priced used diff is a gamble. Many are out of cars for issues they had. If you post pictures of this diff with the cover off I can tell you a lot more, if the seller won't pull the cover keep looking or learn how to correctly build these to last and one hint it is more involved than a few hours of labor and new bearings. If you want new gears that you will have to settle for imported ones since there are no more usa made gears that I am aware of.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
1969 Corvette differential codes
