Differential? And transmission question.

Well, after taking my '75 Stingray to my mechanic to find out what a 'clunking' noise was coming from the rear of my car, I was told it has to do with the 'differential,' and that it would require a transmission specialist to take care of it.

I'm just curious if you guys can tell me exactly a differential is, and how long I can reasonably drive it around before I need to get it fixed. (I was told to no longer take it on the highway.)

From a older post on this list, I see that it might cost around $1000. Does that sound about right?

What I'm also wondering, is if this is basically related to the transmission, is if I should just go ahead and rip out the automatic transmission and install a manual? (I've been wanting to have that done anyway, and hopefully save myself some headaches in the future on transmission maintenance.)

Thanks for any kind advice!

when does it makes the noise? Does it do it everytime you accelerate? You might wanna check the U-joints and/or wheel bearings also.

Yep, the clunking noise happens mostly during acceleration, usually around 20mph, and more recently, even after the car has been warmed up (i..e, shut off, then turned back on). So, it'll do it while it's idle, if it's been warmed up. But I'll definitely have the u-joints and wheel bearings checked out at the same time. Thanks for the tip!

If I were you, I'd check all the U-Joints before I suspected the rear end. Vettes are notorious for destroying U-Joints. I've replaced 2 on my vette and have 4 more to go! Joe