I need to replace a rear wheel bearing on my 1985 300D. I looked at the diy article and not exatly sure what the gauge is for. Also can it be done without the special socket that is shown in the diy. Also do I need to purchase the entire wheel bearing kit or just the bearings themself.

The dial indicator is to set the end play of the bearings. You definitely will need it. Can't really be done by feel. You will also need the pin socket. No way around it.

Not buying the kit is false economy, IMO. I suppose you could get away with not replacing the seals, but why? Also, the crush washer cannot be reused. In fact, it is a good idea to order a couple of extras should you inadvertently overtighten the bearings. They are a one-use item and it is really easy to overtighten if you haven't done this job before.

What makes it odd to understand it that when you assemble it before you install the inner Bearing (the one facing the differential on the side the Retaing Ring screws onto) you slide on a metal Crush Ring onto the Hub Shaft.
When you tighten with the Socket/Pin Wrench the Retainer Ring Pushes the Bearing and crushes the Metal Crush Ring you slipped on. How much that ring is crushed determines the end play of the Hub and Bearing assembly.

If you tighten it too much and there is not enough end play you have to start all over again.
Take it apart and get a new Metal (crush) Ring. If you need to use a Slide Hammer or otherwise have to beat it off you stand a good chance of damaging one of your new Bearing Sets that you just installed.

This is why the Special Socket and Dial Indicator are important. You need the Special Socket so that you can control how much you tighten it and you need the Indicator to tell you what is happening when you tighten.

On eBay the Socket/Pin Wrench sells new for about $30+ about $9 shipping.
There may be some for rent in our Tool Rental Program.

You will need to convert the inches into mm but the Magnetic Base and Dial Indicator can be had at Harbor Freight for $20-$30 range and at other machinist supply places. Or maybe one of our Members in your area would loan you one.

On the other end of this in a recent thread; even with a new Socket/Pin Wrendh one of our Members is haveing unscrewing the Retaining Ring.

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84 300D, 82 Volvo 244Gl Diesel

Go to the DIY and at the end is a link to the discussion. Click on the link and review all the comments. The adjustment and usage of the dial is covered in the discusion.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car