Author Topic: Wrestling the driveshaft...  (Read 4184 times)

1980sdga

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Wrestling the driveshaft...
« on: 05 June 2011, 06:33 PM »
I've been working on this most of the evening.  I started this morning but other things came up and it was awfully hot this afternoon. I'm trying to get my center driveshaft bearing changed and while it's not that difficult it is a little tedious.

This is the front flex disc which is sort of a PITA:



That's looking from the rear of the car.  There is an aluminum plate above the muffler with 6 bolts that has to be removed and the exhaust has to be dropped as well. Thankfully the exhaust is simple to remove. Just remove the big rubber bands and it drops and the flex pipe from the engine allows a lot of movement.

I couldn't get a full size wrench to fit between the transmission mount/crossmember and the flex disc bolt so I cut a cheap wrench in half to get to the bolt.  I have the front of the car up on ramps and chocked so I jacked up one rear wheel and rotated the tire with the transmission in neutral to index the drive shaft so I could get to the bolts.  I'd set the car down and place it back in park before getting back under it.   So far it's been a lot of jostling and maneuvering so you'll want the car pretty secure to be safe.

This is the locking nut near the center bearing:



That's the center bearing support at the bottom of the photo and the nut that needs to be loosened is the hex in the center. The nut clamps down on some slits in the shaft which allows another shaft within it to telescope.

The worst part has been separating the shaft from the disc without screwing it up.  Even with the bolts out it seems to be stuck like glue...

Update:

Good to know Tom!

This is what all the fuss was about:



You can see the rust around the bushings. That's all it took to stick them together pretty hard. With more serious rust this looks like it could turn into a really difficult job!  I ended up carefully tapping on the washers with a brass punch and they broke loose. I had to raise the car and rotate the shaft a few more times to get them all though  ::)

It slid out the rear and BARELY cleared the parking brake gear.  I was worried that it'd have to come out and it looks like the bolts come from INSIDE the car  :o You'd have to dissassemble the thing which would be a PITA.  Didn't someone say the parking brake stuff had to come out?  Mines a 1980 300SD so imagine you may have to do it on some models.

The black "fish mouthed" hoses coming through the floor pan are the AC drains which started this project...

Here's where I am now:



I have a notchy U-joint so I need to round one up. It looks like the caps are staked in...

I'm just not putting this driveshaft in with a crappy u-joint.  Too much work...

The good news is that my flex-discs look fantastic!  I looked at them through a magnifying glass and they look fine. I was really worried about that. I think I'll just clean them up with some soap and water and ride  8)  I wouldn't worry about it but I sprayed the bolts with penetrating oil and it may eat the rubber.


« Last Edit: 05 June 2011, 07:41 PM by 1980sdga »
Jon


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Big_Richard

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Re: Wrestling the driveshaft...
« Reply #1 on: 05 June 2011, 06:58 PM »
the tubes in which the bolts go thru in the flex disk are a slight interference fit within their respective yokes. Its not unusual to have to bash them apart. if rust is involved it may be more difficult im sure.

1980sdga

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Re: Wrestling the driveshaft...
« Reply #2 on: 05 June 2011, 11:07 PM »
I just did some reading and I guess the U joint isn't considered a serviceable part  :o  MB expects you to replace the whole thing! There is a guy who found a part # and changed it but I understand that the "notch" I'm feeling in the travel isn't a problem.

Oh well, I got a little ahead and ground off the stakes on one cap before figuring all this out  ::)  I'm just going to re-stake that cap and go with the joint that's in there. The part of the joint that I loosened is smooth now so it may just be caked grease that I'm feeling.

I also marked the driveshaft before pulling the halves apart:



I've heard that putting it back together wrong can cause vibrations.
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

Squiggle Dog

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Re: Wrestling the driveshaft...
« Reply #3 on: 05 June 2011, 11:09 PM »
When I replaced my flex discs I had planned on also replacing the center bearing and universal joint, but I read in the manual that they have to be pressed off, then balanced with the propeller shaft.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 350,000+

1980sdga

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Re: Wrestling the driveshaft...
« Reply #4 on: 05 June 2011, 11:17 PM »
When I replaced my flex discs I had planned on also replacing the center bearing and universal joint, but I read in the manual that they have to be pressed off, then balanced with the propeller shaft.

Do you mean the u joint? The whole driveshaft system is so friggin convoluted to me. Just seems like there is so much rubber to screw up and they don't think the u-joint should be easily serviced  ::)

My background is in old US iron which have 2 universal joints. One on a yoke that mates with the transmission output shaft and another on  the rear end. No center bearing.

Maybe that setup isn't ideal with an IRS where the pinion angle doesn't really change.
Jon


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Squiggle Dog

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Re: Wrestling the driveshaft...
« Reply #5 on: 05 June 2011, 11:24 PM »
I think the manual states that even the center bearing has to come off with a press and then the propeller shaft has to be rebalanced to it. I think that the universal joint can be pressed or cut out at the dealer. It all seems scary to me.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 350,000+

koan

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Re: Wrestling the driveshaft...
« Reply #6 on: 06 June 2011, 01:25 AM »
I think the manual states that even the center bearing has to come off with a press and then the propeller shaft has to be rebalanced to it.

I replaced my centre bearing and support, think I just used some sort of puller on it, maybe after cutting the support away.

Don't recall seeing anything about balancing after this job, can't see why it would be required.

I've seen the odd "job" done on tailshafts like welding washers over the caps to hold the universal in place, no doubt balancing would be required after work like that.

koan   
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1980sdga

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Re: Wrestling the driveshaft...
« Reply #7 on: 06 June 2011, 07:31 AM »
Here are the parts:



Time to get this thing back together.

I may change the diff oil while I'm in that area. Wish me luck on that one  :o
Jon


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TJ 450

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Re: Wrestling the driveshaft...
« Reply #8 on: 06 June 2011, 09:15 AM »
Koan,

The balancing refers to replacement of the U-Joint, which is really not a service item... It hardly does anything at all anyhow.

Thus, it refers to balancing of the entire prop shaft.

Indeed, there's no need to use a press for the bearing / carrier... Just a puller. I pressed the bearing on by hand after fitting it to the carrier.

I just "jimmy" the yokes apart from the flex discs with a tyre lever, rotating the shaft as required so nothing gets destroyed in the process.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

1980sdga

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Re: Wrestling the driveshaft...
« Reply #9 on: 06 June 2011, 01:35 PM »
Got it!  Man what a dirty job  ;D  Hot out there too...

This is the C clip that holds the bearing on. It's out of the slot and is near the back of the splined shaft.



I used a chisel to bump the old bearing off:



It wasn't that hard to get off.

New bearing and carrier on the shaft. Note the metal dust covers. There are 2 of them. One on each side of the bearing.:



This is the end of the shaft that mates to the rear end. The transmission end looks the same. You can see the counterbores that Tom mentioned:



I cleaned it up and greased the center and the bolt holes.

Here it is back together. You can see the other dust shield and the rubber shaft seal:



I was very careful not to allow the halves to separate while snaking it through the tunnel over the parking brake gear.  I then tightened up the bolts at both flex discs, tightened the center support making sure it was in a "neutral" position with no binding and then tightened up the lock-nut.  I need to check out my parking brake (Greased everything while I was under there) so I still have the parking brake cover plate/heat shield off.

Both of my shifter bushings were GONE so I replaced them while I was under there.  Had to get a bath before the test drive  ;D

Sorry it it's long winded but maybe it'll help someone else with this job.

Update: I just took it for a test drive and it straightened out a little vibration issue I had. It was real subtle, almost like the AC blower was making a noise. In fact I thought that's what it was until I ran with/without the blower on.  No problems so far...

I'm real happy with my shifter now  ;D  It was REALLY sloppy before but now it's tight!

Here's  a before:



Both ends were the same way  :o

« Last Edit: 06 June 2011, 02:35 PM by 1980sdga »
Jon


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jbrasile

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Re: Wrestling the driveshaft...
« Reply #10 on: 06 June 2011, 03:24 PM »
Nice work Jon and great post!!!

It's amazing how dirty some of these jobs can get...

Tks,

Joe

1980sdga

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Re: Wrestling the driveshaft...
« Reply #11 on: 06 June 2011, 07:23 PM »
Yea Joe, it wasn't really difficult just tedious and gritty. Especially working under ramps.  I discovered I had thse problems when I was working on the AC drains and I'm glad I didn't find any more surprises while doing this job!

The exhaust is original and is appears to be solid although it has a LOT of coarse scaly rust on it.  I pinged it with a hammer and probed pretty hard with a screwdriver and it's in good shape. Mufflers and all. Surprising considering how bad it looks! It's really pitted with rust falling off of it... They must have used really thick tubing.

I also had a chance to check out the transmission and vacuum connections under the car.  I plan on checking all the adjustments at some point.  I noticed that the trans pan is moist and I may have a small leak at the dipstick banjo which I'll have to investigate.

Anyway, On to the next thing!
Jon


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Squiggle Dog

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Re: Wrestling the driveshaft...
« Reply #12 on: 06 June 2011, 08:35 PM »
This will help some day when I replace my center bearing and universal joint. The rubber was holding up well and the universal joint had no play, so I was able to get away with not servicing them (which I am grateful for).

It sure does make a big difference when replacing the shifter bushings, doesn't it? No more sloppy, loose-feeling shifter, mine feels like new now.

The diesel exhaust systems last almost indefinitely due to the fact that the engines produce very little moisture and other chemicals that would oxidize the metal.
Stop paying for animal cruelty and slaughter. Go vegan! https://challenge22.com/

1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 350,000+

1980sdga

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Re: Wrestling the driveshaft...
« Reply #13 on: 06 June 2011, 08:49 PM »
The diesel exhaust systems last almost indefinitely due to the fact that the engines produce very little moisture and other chemicals that would oxidize the metal.

That makes sense. I've had gas burners with exhaust that looked like this and it was rotted through.  I just assumed that mine would be shot because of how bad it looks. I tried to poke holes in it with a screwdriver and hammer figuring I'd need new exhaust. I was really surprised!

The shifter bushings made a world of difference! I've read about bad bushings leading to cars popping out of gear and rolling away  :o  I saturated my parking brake cables with penetrating oil so I'm planning on adjusting it in the AM.  I also sprayed every nut/bolt/cable etc with penetrating oil and I do it every time I work under the car. Seems to help things come apart easier when I have to do repairs.

I plan on keeping the diff plugs saturated until I get around to changing the fluid.  Maybe it'll help...
Jon


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TJ 450

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Re: Wrestling the driveshaft...
« Reply #14 on: 07 June 2011, 01:43 AM »
Great work... I love the post.

That was the perfect time to replace the shifter bushes... It's a real PITA otherwise.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500