Dear Tom and Ray: My name is Emma, and I am 20. I am about to purchase my first car. I have chosen a 1975 Mercedes 240D non-turbo, four-speed manual. It’s going to cost me $1,500 from a dealer. I found his ad on Craigslist. My dad and I went to see the car, (about 2½ hours away from my home) yesterday. Overall, this car is a gem – nicely preserved, and cherry red. Even the air conditioning blows cold! However, when we took the car for a ride, at about 30 mph and above it made a really sharp grinding sound from the back. All signs point to the differential. The noise is emanating from its location, and when we got out and looked under the car, the thing looked icky: Thick grease had oozed its way out and hardened on the exterior. It presumably was dry inside. Not sure, but we think it was a slow leak. So, exercising caution, we did not purchase the car then and there, but rather told the dealer that we would come back later in the week after he had the differential checked out. My dad thinks that it will be OK if it gets some heavy oil put in it. My question is, should the whole differential be replaced? And if so, how immediately should I do that? If the dealer gets the oil changed in the differential, would it be OK to drive for a while? And if I do have to get the thing replaced, is it really worth it? Will it end up costing more than I am going to pay for the car? Please help. Thanks! – Emma
Ray: In my vast experience, Emma, once the differential is damaged to the point that it’s making noise, just putting fresh oil in it – or fresh oil, bananas and sawdust – is not enough to reverse the damage. So, if you’re sure that the noise is coming from the differential, I think you should go on the assumption that the differential is cooked.
Tom: That means you’ll need to replace it in … how long is your drive home? Two and a half hours? You might make it.
Ray: Actually, it could last months or more. But I wouldn’t count on it.
Tom: What you really need to do is get an independent opinion – not from this dealer, who is trying to sell the car, but from someone who is working for YOU. So take it (or have the dealer take it) to a shop you trust (you can use www.mechanicsfiles.com if you don’t know a trusted shop near where the car is being sold) and have your own guy go over the car, bumper to bumper.
Ray: If all that’s wrong with the car is the differential, you’ll want to know what that’s going to cost to fix or replace. Then you can try to negotiate with the seller. So if he wants $1,500 for the car, and the differential is going to cost $1,000, you can offer him $500 and see if he’ll take it.
Tom: Or ask him to replace the differential himself, since he’s a car dealer and presumably has mechanics working for him. And then you’ll give him $1,500.
Ray: But if your own mechanic discovers that the transmission is also limping along, the exhaust is about to fall off, or you need brakes, calipers and control arms, you might decide to walk away and look for something a little less classic. Like a 2003 Corolla.
Tom: Or just get your cars checked out carefully before you buy them, Emma, to minimize the expensive surprises. Good luck, kid. And enjoy whatever car you end up with!