Hi,

I am wanting to replace my center bearing and front/rear flex disc in my 85 300D. I have a hum that I strongly suspect is coming from center bearing. But since I am going to have to pull the driveline, I was thinking it would be a good idea to replace flex disc while I am doing the center bearing job.

Can someone give me some tips or tricks to make this job smooth? I am a confident DIYer and have access to auto hobby shop at my AF base with lift.

I would appreciate any comments and how long I should plan for this job. I have already ordered new flex disc, center bearing, center bearing support and bushing, and new shaft bolts from Fastlane.

Thanks,

Morph

I did this job on my 220D last year, making one mistake. I don't know how different the 300SD would be, although I also have an '82 300SD. I replaced BOTH flex disks, bearing holder and bearing.

I had to drop the tail end of the exhaust system a bit to clear the driveshaft. Just remove the rubber donuts, and let it hang.

You need to loosen the parking brake cable - no big deal. Just remember how it goes back together.

Before you remove the driveshaft, which can be done in one piece, you have to remove a crossmember support (I recall). Just a sheet metal bracket (probably holds the bearing support - I can't remember for sure).

The rear flex disk is fairly easy to remove. On my 220D, however, the bolts were a bit tricky in the front. You get new bolts/nuts with the flex disk kit, so you can be ruthless with removal.

When you get the driveshaft assembly out, be SURE-SURE-SURE that you mark the respective alightment of the front and rear sections, so that the driveline will retain as much balance as possible. I DID NOT remember to mark the two sections, so now have unwanted vibration. There are shops that can balance your driveshaft; but, no sense having to do it when it can be avoided. The large nut on my car (and I suspect on most cars) can be loosened by anything, since the nut tends NOT to be very tight. I used large channel locks.

Replacement of the bearing is the hard part. I ended up taking the driveshaft that has the bearing pressed onto it to an independent MB repair shop. The mechanic removed it at no cost, obviously hoping for future business from me. I owe them some work in the future. I sort of expected some finesse; but, the guy just used a big hammer to pound the old one off. I wasn't paying attention when he installed the new bearing, so am not sure if he used the big hammer or actually pressed the bearing onto the shaft.

Reinstallation of the driveshaft with bearing and holder can be done in one piece. If I remember correctly, the final tightening of the center bearing mount should be done after you've driven a bit, so that the holder is properly located with full weight of the car on the driveshaft. There IS longitudinal play in the driveshaft.

This procedure is explained fairly well in the W123 Haynes manual. In my case I had the shop manual for 114/115, which gave a lot more detail.
Good luck.

__________________
Jeff Naumann
Torrance, California
1972 220D 138k miles (sold)
1982 300SD 263k miles
1989 BMW 750iL 183k miles
1993 Dodge D250 Cummins 5.9 202k Miles

I should have read your post a little more careful. Your car IS a 300d, so that the Haynes manual should describe the procedure accurately.

BTW, if you are not experiencing actual "clunking" or vibration, the hum that you hear MIGHT be coming from the differential. Have you checked the oil level? It's easy to check and change. Just be sure that you loosen the FILL plug before draining the oil. Very embarassing to drain the oil and not be able to replace it without flipping the car over.

__________________
Jeff Naumann
Torrance, California
1972 220D 138k miles (sold)
1982 300SD 263k miles
1989 BMW 750iL 183k miles
1993 Dodge D250 Cummins 5.9 202k Miles

If you are going to flip it over be sure to take the brake fluid and engine oil out first...and then remember to put them back .... Greg

As a guy who did this with an OH *****,when the driveshaft came apart as I was extricating it from the parking brake cable,tie the front and rear together with tie wire so it doesn't happen to you too I now have to get my driveshaft balanced as well.
I did remove my bearing with a large three jaw puller,it went pretty easy though,so you could probably tap it off with a hammer,putting the new one back on is easy also.Good luck.

__________________
Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I also did this job a couple of weeks ago, replacing the center bearing and support. What I did first was take white paint like it said in the haynes manual and went from the back end and marked every possible joint all the way across this is important. I also put a small bend in one of my wrenches so i could get to hold the back nut s of the flex plates. I did not have to remove anything I was able to get it all apart in sections . I used a combo bearing puller to get the old bearing out. Take you time and good luck. Hans.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.

240 Diesel,

What were your symptoms before you started the job. I have a whinning/roar at 40mph when I let off the gas. Disappears when I put a load on drivetrain. I can always hear it during decelleration up to about 60. Can't decide if it a rear wheel bearing or center bearing. I am thinking center bearing. I am going to put new pinion seal while I am at it. Cheap piece.

I appreciate everyone comments. I am going to tackle this weekend at shop.

Thanks,

Morph

PS I will try to take pics

Morph, I did a close inspection under the car and tried to move the drive shaft around in the center, right next to the center and support bearing. Lots of free play, the whole rubber inside the support was wasted, wow . I could not believe that the drive shaft did not fly apart. I actually did not feel to much vibration ,or noise, I was surprised , replaced both Items. Hans.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.

240/Morph,

I may have the same symptoms as you. Hollow, creaking/bubbling noise comming from the center of the 300TD when I let up on the accelerator below 40mph. Most noticable at less than 30mph. I checked out the center bearing this weekend. It seemed like there was some play (I could deflect the drive shaft up or down), but it seems like this could be the way it is designed. The rubber was all pretty sound. Apart from a disintegrated bearing mount, is there any other way to check the soundness of this part?

The sound became more noticeable after the tran and diff oil changes that I have done over the past couple of weeks.

Did the center bearing replacement make a difference? Are there any other usual suspects for causing this type of noise?

thanks

Surfblau , I replaced the bearing carrier and bearing together. As the rubber was all dry rotted . I would look close at the rubber with a light as it was a lot easier to see if you have not already done so. Make sure you push up and down on it also. There are lot of things that can cause strange noises and small vibrations try to isolate them as best for starters . Good luck. Hans.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.

The center support rubber failed on my 240D in TN on my way home from the west and the drive shaft made clunking noises. I fixed it temporaryly by putting clothes pin halfs thru the support length wise where the rubber was. This kept the drive shaft from whipping around until I could get home To PA (~1000 miles) with no problems and no delay waiting for parts. Surprisingly, for the spring. all the pins stayed in place. They were the spring type of pins that had a notch in the center. I think that notch is what held them in.

This is what we called in the Army: field expedients in other words make do with what you can find locally when supply can not fill your needs.

P E H