I recently took the 9" differential from my 1970 Mach 1 to a local shop for a rebuild. (It has over 250,000 miles on it with the original gear oil.) It's an independent transmission shop where I've had work done before. Their work is top notch and they have a knowledgeable guy who specializes in differentials.
I talked to the differential guy when I dropped off my 9". I told him in addition to the rebuild, I wanted him to install a Detroit Truetrac and 3.73 gears. (My diff is single track with a 3.0 gear.) He was really cool and said he could take care of that, no problem. He even offered to paint it for me so it would look like a brand new, factory differential.
When the shop called and gave me the price, I was little surprised. They want just over $2000. That does include absolutely everything, to include tax and a 12 month, 12,000 mile warranty. But I still thought that might be a little high considering I found completely rebuilt differentials online for not much more. Here's an example:
Just Rear Ends - Product Display
Now, I understand the Truetrac unit is about $500. And I know I must also pay for the new gears, bearings and whatever else goes into the rebuild. But does $2,000 seem reasonable? I've never worked on a differential. That's why I took mine to a shop. So, I really don't know how much work is involved.
I would appreciate thoughts and experiences here so I can understand and figure out if I'm being overcharged. Or, shoot, they might be giving me a great deal. I honestly don't know. That online differential could be junk and I expect shipping would not be cheap. I don't mind paying a little more to a local shop I know and trust and who can do warranty work, if necessary.