Not to steal the thread, but have a question... just acquired a 81 240D with the 300TD conversion, runs great 4spd car..also got a replacement diff from the owner which he states are more highway"friendly" gears.

I drove it home about 60 miles and agree a 5th gear or higher gearing in the rear would do it some good.

My question, what gear ratio is stock, he believes this set is 3.32 but I havent got any numbers off of them yet.

Looks to be a pretty straight forward swap.

I suspect Mercedes got it really right with their rear cv joints. If you do not drive them too much under lubricated. It seems adequate to just add the oil. In general they may be the toughest part in the car. Rather than using an oil recirculation system but grease instead. I do not believe they could have both lasted the distance or time. For all practical purposes they rate of wear if kept heavy oil lubricated is virtually nothing.

As with many things in life some subjectivity has to be applied. They have to be running for a time in a semi lubricated condition until they are audiable in some fashion. This implication to me is some wear has occurred. How much will vary with circumstances. Yet if they settle down with new lubrication I consider it not is an indicator they need changed.

There is even a too much wear indicator may be present in this type of scenario. If the noise is there constantly all the time. To me running then too dry has been left too long. Taking time to warm them up before the noise occurs to me is an indicator there is not much existing clearance yet or they would not be capable of binding. After they warmed up a little. since your noise starts in about five minutes. I would suspect yours are still pretty unworn. Just do not put off getting some heavy oil injected.

With the thermal expansion of the friction heat. Noise from the first use of the car and constant in nature. I would change them. These joins if properly relubricated say every five years might go an indefinite amount of milage. Well beyond the rest of the car surviving is a strong possibility. Anyways I just add a little heavy oil before one of these cars goes into service. Anything is better than dealing with a road breakdown today otherwise.

I also have no ideal of where the oil migrates to over the years. Probably a tiny amount gets by a seal with time. Another thing or reason they should be on a maintenance list. The original axels with their high quality are really expensive. Plus any road breakdown can cost real money and time before you are mobile again.

Driving a thirty to forty year old vehicle is just a little more demanding to keep reliable. Actually with some effort and time this is achievable in my opinion on these cars. .If the accumulated milage is not really excessive. At reasonable cost and effort. Actually at far cheaper costs than one would expect.

Three hundred thousand is not too high for the rear cv joints. In my opinion. Tragically I never believe the odometers unless there are some indications they might be right are present though. Even then it is a tough call at least for me. Instinctivly that you want to believe what you see to me is human. Described as the wearing of rose colored glasses usually I have found pretty accurate.

The ratio is stamped on the rear of the casing. When changing the rear end you need the speedometer from the same car or from another that has the same rear end ratio. You probably have the original 3.69 ratio in the 240d now. The 3.32 ratio mentioned for some reason does not ring any bells for the five cylinder naturally aspired diesel engines. It still might be right though. Check for the ratio on the casing of the rear end you where given. .I found that even the original rear end ratio for the natural aspired five cylinder engines. Like in my 1977 300d seems not quite low enough. Yet I agree the 3.69 is really inadequate. Even for the four cylinder engine. I live close enough to sea level with no really serious hills. Needs can vary on location topography altitude and climate. Use as well. If you had a turbo engine I would jump to the 2.88 without a second thought.

Barry thank you and this is a 240D according to the VIN decode it was a NA 4cyl diesel but has been swapped to a 300TD turbo diesel engine....I will see tomorrow what this other diff has stamped on it.

Thank you again...