So I’ve got the rebuilt iron diff back with 3.73’s from Gary to put into my ‘81. I’ve seen where others have modified the front mount to match up where the D44 attached but I’d prefer to not cut it up as it just doesn’t look clean. Maybe I’m being too **** but I hate the look of chopped up parts. So before I look into having something made, thought I’d check the hive and see if anyone already makes one for the iron diff swap or knows someone who can?

Thanks folks. Can’t wait to get this installed and on the street again!

 

I think Van Steel makes an adapter for this.

 

Oh that would be awesome!. I will give them a call. Thanks!

 

https://www.corvetteforum.com/forums...an-82-a-2.html

 

How much horsepower do you have that you need an iron differential?

 

I don’t have any dyno numbers but I’m running a fairly healthy LS. My original was leaking so I wanted to take the opportunity while I had it out to swap out the original 2.87’s for 3.73’s. Finding parts and competent rebuilders of the aluminum diff was proving difficult. And those tiny little 1/4” screws holding those 1310 ujoints on the half shafts don’t inspire confidence. I found a complete rear out of a ‘79 for 400 bucks and now I have a stronger diff rebuilt by one of the best, 3.73 gears, easy parts availability, and stronger 1330 ujoints so I don’t have to worry if I want to have a little fun 😉.

Other than modifying the front mount and driveshaft, it’s pretty much been a bolt in. And I did learn from @76strokervette Van Steel and Duntov makes the front mount so that’s taken care of.

 

If you don't mind me asking, how much do you have in it total? You said 400 for the diff, how much for the rebuild and mount? This is on my radar as well. But how hard is it to find a donor diff, and what years fit?

thanks

 

I guess Mike Dyer is out of business? He rebuilt my Dana 44 to handle 550+HP. Your way is probably the only way to go now.

 

I found a complete rear locally out of '79 but I believe all C3 years iron units and most rear parts will swap. Just have to be patient because you need the diff, the half shafts, strut rod bracket, and strut rods. If you're really serious I'd reach out to Gary for his advice on which years are the best donors.

You can use your existing TA's as they are all the same but since what I found was complete, I rebuilt the bought units so I could continue driving during the process. In addition, you will need a new front mount or you can modify your existing one which some folks do. You may have to lengthen your driveshaft as the iron pinion sits 3/4" further back than the dana 44. I could have gotten away with just letting the trans yoke slide out 3/4" but I also wanted to get rid of the really weak 1310 u-joints so I had a new driveshaft made 3/4" longer and with 1330 u-joints. If you use your old one then you'll need a 1310/1330 u-joint for connection to the iron diff. You can use your existing batwing but you'll need shorter bolts or the bolts off the donor iron diff cover. Other than that, it's not a difficult swap.

The driveshaft cost me $248 including paint and balancing and conversion to the 1330 u-joint including u-joint installation. The diff was a different story though. Even though the iron diff is stronger, it still has it's issues and I ran into one of them which was the posi unit window was cracked so the posi case was no good. I didn't realize this until it was already on Gary's workbench. Thankfully he carefully checked it out and found it before it was too late. I sourced another used posi unit with no cracks but that one also turned out to be bad due to another issue with it. The good news was it already had the correct 3.73 gears so that was a bonus. Gary also discovered it had 2 different year side yokes in it and one of the bearing cap threads was pulled which he re-drilled and used larger 1/2" bolts for. Gary determined it was a standard vendor rebuild unit and poorly done at that. I did check my aluminum unit and although it made no noises or chatter, the center pin was chewed up and probably something would have failed sooner rather than later. So in the end, all I can say is that corvette diffs are a unique and squirrely beast and for the money you're going to spend, don't just trust it to anyone. Anyway, I have about $2500 into the rebuild but that includes 2 bad posi units, the driveshaft, brand new Eaton posi unit, and the rebuild/tuning/polish services from Gary. It was more than I had originally budgeted but at least I know it's properly built and tuned and will last. As I told Gary, I don't want to have to go through the process again so let's do it right once even though it cost me more than I thought it would. You might be able to spend less but you'd be rolling an expensive set of dice to save a few bucks. Best part is she will now run like a corvette should with those 3.73's behind the LS. Good luck!

 

Can't speak to that but I've heard things have changed...And I doubt it would have been any cheaper or easier as I would have had to get a new ring and pinion set as well and from what I've been told, they are made overseas now and you can't get the old US made ones unless you get really lucky. Plus you still have to deal with those really wimpy 1310 u-joints...

 

I upgraded to 1350 flanges, so no problem there.

 

Smart man. There is no cheap way around a C3 rear no matter how you slice it. I sometimes wonder if the IRS of those days was really worth the effort over a well done live axle...

 

I hope we never have to upgrade again!