1987 300D auto trans problem - PeachParts Mercedes-Benz Forum

dlachance · #1 09-02-2014, 10:49 AM

Hello -- I'm new to this forum, and I'm hoping someone will be able to give me some advice on a 1987 300D that I'm considering. The seller says that it will not move in forward or reverse, that it's as if the car is in neutral all the time. He says the problem is "a rubber torque absorber that connects the engine to the torque converter," and advises me that the transmission has to come out for it to be repaired. In my limited research on the subject, I can't find any reference to a "torque absorber." Is there such a thing? I don't believe he's talking about one of the flex joints on the driveshaft -- he's adamant that it's a connection between the engine and the torque converter. The car is three hours from me, and I haven't had a look at it yet. All good advice gratefully accepted!
Thanks,
Dave

dlachance · #2 09-02-2014, 11:08 AM

Is it possible he's referring to the flex plate? I've never heard one called a "torque absorber" before. And, of course, a flex plate isn't made of rubber ...
Dave

jbrianfoto · #3 09-02-2014, 11:34 AM

The torque converter is made of metal, looks like a big fat metal doughnut, and is situated inside the bell housing of the transmission. It is bolted to the flywheel on one side, and connected to the transmission center shaft in it's center (that's a splined shaft that actually drives the transmission). In order for it to couple the torque of the engine to the rear wheels, it must be full of fluid.

With the engine running and in neutral, check the trans fluid level. You may likely find that it is dry. If the fluid level is normal - you have another problem.

At the rear of the transmission, where it connects to the front end of the drive shaft, there is a Flex-Disc which is made of reinforced tire rubber. It has 6 bolt holes which are lined with steel shafts. This disc couples the trans to the drive shaft (there is another one at the rear of the shaft where it connects to the differential). These do fail too, but when they do, it can be catastrophic - much damage to the underside of the car and in some extreme cases, injury to the occupants. I would be surprised if the lack of motivation in this car was being caused by the Flex-Disc.

If you really want the car, and the price is right (and you can tow it home) - you can count on spending about $1500 to replace the trans (if you do all the work yourself and can find a good deal on a replacement trans).

Shoot me a note if you need help - I just replaced the trans in my 87 sedan 5 months ago.

vstech · #4 09-02-2014, 11:59 AM

if it's between the engine and transmission... it'd be LOUD if it is broken...

if the trans does need to come out, it could be the pump ears, the TC, the flexplate, etc... input shaft...

start the car. set the emergency brake, put the car in L and look under the car to see if the drive shaft or one of the axles is turning...

a common failure on this chassis is the shafts failing. resulting in the car acting like it's in neutral.

put in L, then put back in P... if it makes a LOT of noise, it's the axle...

Mxfrank · #5 09-02-2014, 09:05 PM

It's not a rubber flex disk, the owner is blowing wind. If he thinks it's something simple, let him fix it. I wouldn't touch a Benz with a bad transmission...

dlachance · #6 09-04-2014, 12:24 PM

Thanks to everyone for your help. vstech, take a bow. It wasn't the transmission at all, but a broken rear axle, the one on the passenger side. The seller was really great about it, and stood by his $900 asking price, so we have a deal.

vstech · #7 09-04-2014, 01:39 PM

cool deal! they are relatively simple to change... YOU WILL NEED A PIC AND A LOT OF BRAKE CLEANER to get the bits out of the axle stub bolt heads. you will also need an impact wrench and an XZN tripple square 8 or 10mm socket... NOT TORX if you decide to get a new axle, DO NOT USE CHEAPO AUTOPARTS STORE NEW AXLES!!! they are junk.
if you want new, go to MB, or order from our site here.

if you want to go used, from a junk yard, take a pair of dikes to cut the band, and pull the boots and visually inspect the axle shaft before you bother purchasing it... 90% of the axles will be badly rusted and ready to fail.

scottmcphee · #8 09-04-2014, 02:54 PM

Or you could use a pair of pliers to squeeze the boot band as if you were clamping it "more shut" and when you have the necessary slack can lift the end of the band up over the barb holding it there in the shut position. Re-usable this way.

vstech · #9 09-04-2014, 03:19 PM

Quote:

Originally Posted by scottmcphee

Or you could use a pair of pliers to squeeze the boot band as if you were clamping it "more shut" and when you have the necessary slack can lift the end of the band up over the barb holding it there in the shut position. Re-usable this way.

you are more talented than I...

jay_bob · #10 09-04-2014, 04:22 PM

Quote:

Originally Posted by vstech

cool deal! they are relatively simple to change... YOU WILL NEED A PIC AND A LOT OF BRAKE CLEANER to get the bits out of the axle stub bolt heads. you will also need an impact wrench and an XZN tripple square 8 or 10mm socket... NOT TORX if you decide to get a new axle, DO NOT USE CHEAPO AUTOPARTS STORE NEW AXLES!!! they are junk.
if you want new, go to MB, or order from our site here.

if you want to go used, from a junk yard, take a pair of dikes to cut the band, and pull the boots and visually inspect the axle shaft before you bother purchasing it... 90% of the axles will be badly rusted and ready to fail.

Don't you also have to remove the ginormous nut on the wheel end of the shaft behind the brake disk? That takes a huge socket (can't remember the size, I'm on a plane again) and the mother of all breaker bars! 240 N-m factory spec torque on that nut...or am I nuts?

jbrianfoto · #11 09-04-2014, 07:25 PM

If the rest of the car is tip top, you got it for a pretty good price. Do you have it home yet? It would sweeten the deal more if it has a newer head installed already. Do post some photos, include the engine bay. We have some really sharp people here, they can tell a lot about a car like this from photos.

Congrats on landing a deal you're happy with on a good car!

vstech · #12 09-04-2014, 08:20 PM

Quote:

Originally Posted by jay_bob

Don't you also have to remove the ginormous nut on the wheel end of the shaft behind the brake disk? That takes a huge socket (can't remember the size, I'm on a plane again) and the mother of all breaker bars! 240 N-m factory spec torque on that nut...or am I nuts?

Yup, 30mm 12point socket is needed, and a "ginormous" breaker bar... Be SURE you un-bend the locking tab before you attempt to loosen the nut...

scottmcphee · #13 09-04-2014, 09:07 PM

Here's a tip too.. The left and right axles are interchangeable. So grab the axle off the passenger side, and you don't have to deal with a muffler getting in your way. Install it on either side of your car that needs one. If you do swap sides, thats great because the axle will have practically no wear on the cv joint going in that direction. It's a way of stretching more life out of an axle. Pro tip!

dlachance · #14 09-19-2014, 02:18 PM

Thanks, everyone, for your help! I can see I came to the right place for advice.
The car is home now, thanks to a friend with a truck and trailer. The passenger-side axle had snapped near the outer CV joint, and was being held together by the rubber boot. One new axle later, I was cruising up and down the street! Very happy, so far.
There's more still to do, besides a thorough cleaning, inside, outside and underhood. The glow plug light does not come on. The engine will start, and fairly quickly, and it runs rough for a couple of minutes until it's warmed up. I installed a proper fuse in the relay, rather than the piece of wire a previous owner had installed, and I have six new glow plugs ready to go in. I've read the many posts about glow plug replacement, and I don't expect to have a problem there.
The OM603 has a #22 cylinder head, so I know there's been work done there (the car came with no paperwork).
I'll post some photos when I get a chance. It's Astral Silver Metallic, with a blue MB-Tex interior.

dlachance · #15 09-19-2014, 02:25 PM

By the way, the locking tabs on that 30mm nut were well and truly secured! It took a hammer and chisel to get them out of the way.