A Hint at My Next DIY Pictorial - PeachParts Mercedes-Benz Forum

Ken300D · #1 01-20-2003, 07:52 PM

The picture is probably the biggest hint. Too late to turn back now! Since the job is not complete, I can ask for suggestions. I'm thinking that pressing in the bearing cups on the new U-Joint is better than driving them in with a hammer - right?

Getting the old U-Joint out was loads of fun, but that's a story for the finished DIY product. It's not that hard with the right technique (think "Dremel tool").

The old U-Joint was worn enough to have "center detents" where the bearing surfaces were worn. I don't think there is really much movement in the U-Joint, so the same roller bearings stay in place without moving around the cup - so they eventually wear. At least it was not rusty / dry like some I've seen.

Ken300D

engatwork · #2 01-20-2003, 08:03 PM

Pressing them in will be better than using a hammer. Were you able to find a new "rubber" piece that goes over the splines? I have this job ahead of me on the 300D after I put the engine and tranny in. When will you have the diy page complete? What's the part number/source for the universal joint?
thanks

Ken300D · #3 01-20-2003, 08:19 PM

Well, today was warm and sunny - it felt like a heat wave at 45 F. Not going to see that for awhile again, so I'll bet that ground hog up in PA gets out before I get this done!

In addition to the U-Joint, the driveshaft is getting a new center bearing, center support bushing, and the dust cover over the splines. Those parts are available on FastLane. The dust cover is now a harder, more durable plastic that should last a long time.

I've been all over the Internet looking for the U-Joint and found a source that may not be "renewable". It may have been one-of-a kind. But I have the Lobro part number, and we may be able to cross-reference. I also have some digital calipers on the way so measurements can be taken before the replacement goes in.

I should charge a few bucks via PayPal for the Lobro part number,

but I'll post it later. Maybe we can all start looking for a good cross-reference or a source for Lobro in the USA.

Also, I'm going to use a press to get the center bearing into its support bushing. I just don't think I got it in there straight the first time. If you can see it is uneven as you turn it around, its going to vibrate!

So, I had to tear the whole thing out of there again. This time its an entire rework.

Ken300D

leathermang · #4 01-20-2003, 08:24 PM

You don't have to have a " press"... you can do it with a vise...

We had a minor heat wave today also... about 75 degrees F... very nice....

Ken300D · #5 01-20-2003, 11:46 PM

I was doing some more research on-line based on the Lobro part number, and came up with this:

The box says Lobro U728/4

I did a search on Lobro U728 and came up with this German parts house link:

http://www.genoparts.de/html/catalog_eng_.html

Third item down on the left is that U-Joint part number. HEY! Notice it has a Mercedes part number associated with it?

So I went to FastLane and plugged in 123 410 01 31

BAM !!

There's a universal joint - - -

However, the Lobro 728/4 that I have is "new old-stock" and it doesn't have any grooves, clips, or grease fitting. I think that's a grease fitting anyway - - -

I can't see how the clips would fit or work. Perhaps they are not used. I'll post dimensions of the "old" U728/4 so that anyone getting this part from FastLane can have a reference.

Ken300D

rwthomas1 · #6 01-21-2003, 11:25 AM

I have had good luck pressing u-joint cups in with a large C-clamp. Make sure the yoke bores are good, clean and free of burrs. C-clamp offers more "feel" than a press. RT

engatwork · #7 01-22-2003, 06:49 AM

Is the spline dust cover the same as the "driveshaft support boot". Do you have a p/n for it?
thanks

Ken300D · #8 01-22-2003, 07:43 AM

Yes, Jim, that's the correct item name on FastLane for the boot that goes over the splines. When you get to the individual part listing, there is a picture. And if you click on the picture you get a larger picture of the part.

It is now a somewhat harder plastic that has an accordian-style bellows for contraction. It is a good fit and should not decay like the original rubber.

I'm tempted to get the FastLane U-joint just to compare the dimensions and see if the grooves and clips will fit inboard of the driveshaft flanges. That would eliminate the need for re-staking the replacement U-Joint.

The Dremel tool was used with a small grinding stone to remove as much of the old staking metal as possible around one cup of each old U-Joint axis. Then I used a hammar and bolt to push the whole U-Joint in that direction. At the push limit, you get about 3/8" of a cup sticking out. Clamp down on that with a vice and then drive the driveshaft flange away from that cup with a large bolt or steel rod. That will pop off that cup - then you can drive the U-joint back in the other direction enough to release it from the driveshaft flange. Then you can drive out the remaining cup. Repeat for the other U-joint axis.

You can't get all of the old staking material out (until the cups are removed) but you can get it so thin that the cup can be driven past it.

I feel a tremor of business environment change headed toward those driveshaft rebuilding houses that charge $600 for a Mercedes driveshaft rework! The one thing they CAN do is a balance. I'm hoping not to upset the original balance with just a U-Joint replacement - and if I do I'll go with the large radiator hose screw clamps to work on the balance.

Ken300D

Diesel 924 · #9 01-22-2003, 10:00 AM

If you don't knock any weights off the shaft or BEND the shaft by accident, the balance should not change. I've changed dozens of u-joints and never had a problem, just never in a MB.

Ken300D · #10 01-31-2003, 08:24 AM

Here are a few comments on progress:

The 12-Ton press from Harbor Freight arrived and I got the center support bearing pressed into the bearing support bracket. Yes, I know a press is overkill for the job. However, I had such a hard time doing this on the first try with a vice, and I didn't get it straight, that I wanted a press. Besides, if this works I'm still ahead on a driveshaft overhaul, and I can do ball joints and the like later.

The bearing support bracket received this time was FEBI brand. Far superior in construction tolerances than the no-name brand received on my first center bearing replacement attempt. It was extremely hard to get the bearing into the no-name support bracket. With the FEBI, it was an easy fit - you can probably use a vice to get the bearing in a FEBI support.

Next, I went ahead and ordered part 123 410 01 31 U-Joint. What I received was a GKN U721, marked 111 410 00 31. It is not a fit for the OEM driveshaft. Here are the measurements taken with a caliper:

New Old Stock OEM Lobro: 24.07 mm x 74.2 mm

GKN U721: 26.03 mm x 70 mm

The first number is the diameter of the four "barrels" and the second number is the measurement all the way across the U-Joint.

It might be possible to make the GKN U721 fit if the driveshaft yokes were machined out 2 mm to make the four "barrels" fit. I don't want to do that. The measurement taken of the driveshaft yoke diameter was 24.04 mm.

The GKN U-Joint is good quality, with a grease fitting. Too bad its the wrong size - perhaps with the OEM measurements a proper GKN can be found. I'll post close-up photos of the OEM Lobro and the GKN later.

------------------

Bottom line:

Try to get a FEBI center support bracket.

Don't get the 123 410 01 31 part.

Ken300D

GregS · #11 01-31-2003, 02:08 PM

Wait a second, do w123 u-joints have grease nipples? I see one in that picture, but I never knew there was one on my car. If so, I guess I better get under there with my grease gun!

GregS
'84 300D, 173k
'90 300CE, 161k

engatwork · #12 01-31-2003, 03:26 PM

The new ones do come with a grease fitting. Once you have greased it you are to remove the fitting and plug it.

Ken300D · #13 02-08-2003, 12:06 PM

Here's a picture of the two U-Joints under discussion.

The one on the left is the new old-stock Lubro U728/4. I found out the official specs on size for this U-Joint are 24mm x 74.5 mm. So to find a modern substitute I suggest using those measurements.

The one on the right is what I got by ordering the MB part number discussed earlier. It is a GKN U741. Note the grease fitting - it is set the wrong way to be of any use. You'd want it to point exactly half-way between two barrels so you could get a grease gun on it while assembled into a driveshaft.

Ken300D

Ken300D · #14 02-08-2003, 12:14 PM

Here's a picture that shows the reverse of the GKN U741 part. Note the extra metal that's in the form of a cross. I believe this is meant to be a balance for the weight of the grease nipple on the other side. It's a nicely made part - and is labeled "Made in Japan"

Too bad its not a direct replacement - hopefully GKN has something in the proper size......

Ken300D

Ken300D · #15 02-08-2003, 12:23 PM

Not the greatest picture, but you might be able to see the U-Joint on the right has a slightly larger barrel/bearing diameter, and is a little shorter in span (all the way across). This makes it unusable as a direct replacement, and would require machining the driveshaft yoke to be used. Better to find a more direct replacement.......

Ken300D