Flex Disc Help Needed - PeachParts Mercedes-Benz Forum

psaboic · #1 12-26-2014, 07:52 PM

Need some help on this. Today I finally got time to work on replacing the flex discs and the center bearing on my 83 300D. I got the drive shaft apart and all taken out, got the new center bearing put on and started putting it all back in.

Currently the drive shaft is back together and partly in the car (yes I marked it before I took it apart and put it back the same way),but here is where the problem starts. I cannot get the drive shaft and new rear flex disc compressed enough to fit at the differential yoke. It seems to be about 1/4" too long even when prying on it with a flat bar.

At this point the new front flex disc is attached to the transmission and the front part of the drive shaft is connected to the new front flex disc. The six bolts at the front flex disc are snug but not torqued down. The center bearing is not bolted up at all and the transmission mount brace has been disconnected and removed. The new rear flex disc is bolted up to the diffferential yoke but not torqued down. Lastly the big 46MM adjusting nut at the driveshaft halves is completely loose.

What do I need to do to get this last 1/4" of clearance to get the rear of the driveshaft to fit? Is it as simple as torquing all the front flex disc bolts, or attaching and tightening the 46MM adjusting nut, or??

It is really frustrating to be this close. Fortunately, I have a back up car to use right now but I would like to get it done soon, according to the weather we have about 3 days of solid rain on the way.

Thanks for any and all help

Glenn

compress ignite · #2 12-26-2014, 08:04 PM

1. Did you completely GREASE the Spline-ed Shaft central portion of the D.S.
It should be able to compress enough to allow you installation.

2. You are aware of the "Centering Bushings" at either end of the D.S. ?
They fit into the Yoke @ the Tranny end and whatever is @ the rear
that the Flex Disc attaches to (Another Yoke) They must be greased also.

compress ignite · #3 12-26-2014, 08:17 PM

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Chassis/41-050.pdf

I do know you don't want to "Booger Up" the "Centering Bushings".
They are a bear to remove and COSTLY.

compress ignite · #4 12-26-2014, 08:19 PM

It seems raising (Jacking up) the Tranny after loosening or removing the
Tranny mount might help.

psaboic · #5 12-26-2014, 09:00 PM

Thank you for the advice. Yes, I did grease the splines and also both bushings at the end of the drive shaft. I did have the transmission supported by a floor jack and a block of wood when I removed the transmission bracket.

I'm thinking maybe connecting the two driveshaft halves with the 46MM adjusting nut might shorten it a bit to get it to fit. Or jacking up the transmission with the floor jack may do it. Otherwise I am left with prying the hell out of it with a flat bar (which I really do not want to do)

Glenn

mach4 · #6 12-26-2014, 09:16 PM

Quote:

Originally Posted by compress ignite

I do know you don't want to "Booger Up" the "Centering Bushings".
They are a bear to remove and COSTLY.

They're not all that costly - $12 on this site and under $10 at at least one other site - granted, that's for a URO unit, but hey, I doubt they can screw up a simple metal tube. In fact, that's what I used when I replaced mine. And they're not all that bad to replace. You've got to drill two holes and use a pry bar, but nothing like other common repairs most of us have participated in with these beasts. All that said, no you don't want to booger up the centering bushing if you can at all help it!!

Here's how in case someone needs it. Installation is just a few taps with a dead blow hammer and an appropriate size mandrel (socket).

SD Blue · #7 12-26-2014, 09:35 PM

I'm having difficulty picturing where the problem is. If the locknut is loose and the carrier bearing isn't attached, are you saying the driveshaft won't compress?

The only thing that comes to mind is if there was grease that got on the end of the shaft, it might cause it to act as a piston and stop the shaft from compressing.

Is the rear differential suspended?

psaboic · #8 12-26-2014, 09:47 PM

Yes the rear differential is suspended. I put some grease on the splines, but did not put a ton on there so I don't think it is what is keeping the shaft from compressing. Will the adjusting nut compress the shaft halves if it is tightened, or keep it from compressing? I know the adjusting nut boot did kind of get in the way when I was taking it apart, but I really doubt that is the issue.

Glenn

TheDon · #9 12-26-2014, 09:55 PM

I had the same issue when I did mine a month ago.

I didn't tighten the 46mm nut until after I got it in place and I also lifted the transmission. It takes some creative swearing and finagling but it will go home.

Carpenterman · #10 12-26-2014, 10:09 PM

I know it doesn't make any sense, but I always found it easier to install with the rear flex disc mounted to the driveshaft rather than to the differential. It still takes a bit of a pry with a crowbar levering against the input flange ear and the flexdisc.

Frank Reiner · #11 12-26-2014, 10:21 PM

psaboic:

A second for Carpenterman's suggestion; also install the front flex disc to the front shaft. Then, after lifting the rear shaft into the tunnel, slide the splines completely together, and bolt the front flex disc to the trans flange. It will now be much easier to bring the rear connection together. The center bearing support is the last to be bolted up.

psaboic · #12 12-26-2014, 10:29 PM

Don, Carpenterman, and Frank,

Thanks for the advice, I will give it a shot by jacking up the transmission a bit, and also take the rear disc off of the differential and instead put it on the driveshaft first and try it that way. I think it is definitely going to take some creative swearing and horsing around to get it in.

Also Frank that is exactly how I put on the front disc.....first to the shaft, then lifted it all into place and bolted the front disc to the transmission.

Anymore suggestions are always welcome......

Thanks folks.

Glenn

BillGrissom · #13 12-26-2014, 10:37 PM

I disconnected the drive-shaft at the rear 4 months ago when I towed my 1985 300D. I re-installed it at night in a parking lot. The left rear wheel was on a curb and the body jacked up on the right side. I put the rubber disk on the drive-shaft end (should have left it there while towing). I was able to pry the drive-shaft forward enough to barely slip it into the differential's yoke with only a little swearing. Seems having both rear wheels hanging would make it easier. Sounds like you have a new front disk installed (stiffer), so might be tougher.

psaboic · #14 12-26-2014, 10:41 PM

Well, I have the rear end on jack stands so both rear wheels are hanging, and it has a new front disk so...............did you pry with a flat pry bar or a crow bar/wrecking bar??

The Gears · #15 12-27-2014, 02:02 AM

Don't screw up the job prying and banging anything.
Just drop the diff on a floor jack, just a couple of bolts.
Drop it till the emergency cables are getting tight. You can then just slide the centering pin into the hole.