It clunks as I apply brake and slow down. How to tell if it’s differential or axles?

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95 e320,87 sdl,79 300sd

It could be the sway bar bushings at the frame as well as sloppy sway bar links at the front. If so, those fairly easy fixes.

There is also a rear and 2 forward sub frame mounts.

Rear trailing arm bushings.

An easier one if the rubber on shock absorbers falls apart or gets too compressed, they and cause noise.

There is also the rubber muffler hangers that rot out.

Lastly it is simply hard to determine accurately where noise is coming from.

Not with a Mercedes but this is a humorous one. I had a noise in the rear, and it turned out to be something moving around in my trunk.

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84 300D, 82 Volvo 244Gl Diesel

That’s funny. I’ll get it up in the air and investigate

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95 e320,87 sdl,79 300sd

First remove e v e r y t h i n g to see if it is something rolling around.

Have someone get in the car, start it, hold their foot on the brake hard, put it in D and apply the accelerator a little to power brake the drivetrain. Whilst they do this stand off to the side watching to see if either wheel has excessive fore or aft movement. Repeat this in R.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

It could also be that someone forgot a shim when they replaced an axle. That one is easy to check. Grab each axle with the car on level ground in neutral and try to move the differential end in or out. If its missing a shim you will be able to hear the axle clunk as it slides in and out. It also happens when the differential is unloaded when decelerating.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

What ratios diff can I put in my 300td?

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95 e320,87 sdl,79 300sd

Two thumbs up for that.

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84 300D, 82 Volvo 244Gl Diesel

I worked briefly for a school district. In one of their cargo vans some of the large metal tools inside had hit the wiring and did what appeared to be a taillight sort circuit.

My neighbor was having a similar issue, and I told him to look for that sort of short circuit from stuff in the trunk and sure enough that was the issue. Note that in the past there was no blown plastic trunk liners.

I had an issue where something in the trunk pulled the wiring loom off of the trunk hinge and the wire got caught in the hinge and the action of the hinge severed the wires.

And with all of that I have to say my car trunks are a mess of stuff inside of them. I am a slow learner.

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84 300D, 82 Volvo 244Gl Diesel

All the W123 turbodiesels had a 3.07 differential except the 1985. That was 2.88. The speedometer is geared to the diff ratio, so that makes it good to stick with stock. The ratio is stamped on the diff at the lower left just outside the cover plate. But do what everybody else said and make sure you correctly identify the problem before spending time and money.

My diff is definitely bad. Had it on a loft and we could see all the play at the shaft at pinion. The diff is a used one no stamp on it. I could only get a 2.88. I don’t care about Speedo

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95 e320,87 sdl,79 300sd

A 2.88 will lower the RPM's on the highway but will give slightly less acceleration than the 3.07.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer