detailed tranny problem 87 300e

[dirtysocks]

The troubled transmission in my 300e is the last thing that has to be fixed and then my car will be 100%, and then it's just maintenance, hopefully.

Well, I guess I'll get into it. when cold (upon start up) it flares bad from 2nd to 3rd (I know it starts in 2nd), and shifts hard from 3rd to 4th. When warm, it shifts pretty well from 2nd to 3rd, but still quite hard from 3rd to 4th (this is especially bad when it downshifts to 3rd, then back up again, say when merging from an on-ramp). I strategically adjusted the bowden cable and vacuum modulator t today, making small adjustments to each, and then driving a bit to see if there was an improvement. It got a little better, but not much being that to drastic an adjustment caused other adverse effects upon shifting. Actually the shifting qualities were a bit erratic, with some good shifts and some bad as I was driving after each adjustment.

Anyway, the vac modulator line seems ok as far as I can tell. Am I right in thinking that the other end has a rubber u-shaped boot on it and is connected to a metal nozzle in front of the oil filter? no need to respond to this unless I am wrong. Also, I recently changed ALL the fluid and filter, with no real improvement.

There is an odd noise when the tranny is about to shift, or sometimes right after it shifts. My Dad described it as and thinks it is a spring stretching and compressing again.

I smell burning tranny fluid at times, not overwhelming, but it is there. Whenever I look under the car, there is a drop of tranny fluid sitting upside down on the two rear bolts (13mm) that hold the transmission pan on. However, they are torqued to spec, and as far as I can tell the gasket is all lined up as it should be. Besides, my fluid level has remained steady, so there can't be a significant leak. I was wondering if maybe there was somewhere above these two bolts that could be leaking the fluid and causing erratic shifts?

I realize something like this may be hard to diagnose just from my descriptions, and my next step is probably to an MB mechanic. I just figured I would give it a shot on the forum since I have been able to avoid mechanics a number of times already thanks to you all.


As always, any and all replies are greatly appreciated.

[BAd124]

I havent had a ton of experience in this area (probably a good thing) but that sounds like you may need some work on your clutch packs. If the fluid levels are alright and the fluid itself is good (didnt say when the last time you changed it was) I would start looking at the clutches or possibly a broken shift valve. I think there is a known problem with these on the 86 and 87 300E's...I would be interested to see what some others say on this

[psfred]

You should change the fluid and look for metal shavings in the pan. If there are any, it's probably rebuild time.

However, what is the condition of your flex disk? These only last about 60,000 miles in hard use, and cause hard shifts, especially downshifts. Bad diff mounts will also cause the diff to bounce pretty hard on shifts (thumps in the rear), and all can sound funny.

Replace the little rubber connector on the modulator line, it's probably leaking. In fact, inspect and replace if necessary ALL the vacuum lines, including the idle control valve hoses. Vac leaks will play merry hell with fuel mixture, and that will cause all sorts of vac variations, hence hard shifts sometimes and soft ones others.

Peter

[dirtysocks]

I also forgot to mention that occasionally when I put the car in reverse, there is a terrible squeaking and clunking. It stops abruptly when the car actually engages into reverse. Sounds pretty bad but it only happens occasionally. I have not heard it since I adjusted the modulator, but it's only been a day.

I also noticed today that now it seems to be spending to much time going from 2nd to 3rd, and not much at all from 3rd to 4th. A few times the engine would rev (or flare) really high going into 3rd, and then clunk almost immediately into 4th. Should I continue adjusting the bowden cable to try to remedy this? which way would I turn the yellow threaded collar at this point?

All replies are greatly appreciated.

[dirtysocks]

I changed the fluid about 5 months ago. There was a thick, grey, sand-like substance in the bottom of the pan. It took quite a while to clean it all out. I thought it was just dirt or some other type of natural deposit at the time. I suppose it could have all been metal shavings. I was not even considering that there could be shavings in the pan when I did the fluid change, so maybe they were and I did not even know. There was a lot of this matter though (it coated the bottom of the pan), and it was all a dull grey color.

psfred: About how large a quantity of shavings should be expected to be in the pan if there is a problem? Would these shavings be shiny or dull?

[psfred]

The stuff that looks like aluminum paint is normal wear material, but you had more than I would like to see.

Metal shavings are always bad news, at least that means the friction materials is all gone and you are running metal to metal on the clutches. Total failure isn't far away.

Brass shavings mean the pump is gone, bits of other stuff usually means bearings.

Please check your flex disk before driving again, it may be coming apart.

However, if the tranny is making groaning or screeching noises at any time, it's rebuild time.

Peter

[dirtysocks]

crap. I guess I'd better check my funds. If I wait say a month or two before getting a rebuild, will I run the risk of damaging anythng that would not be fixed anyway with a rebuild? In other words, is this going to cost me more cash if I wait a bit, or will any further damage will be repaired with the rebuid anyway?

[dirtysocks]

Flex dic seems good. no visible cracks or separation. Is there something specific to look for to know if it is faulty? I also noticed today that my driveshaft has thick green and orange lines running across it that looks like spray paint. Does this mean it has been removed and marked for some reason, or do they come from the factory with these markings on them? I'm the third owner of the car, and I have few service records on it.

thanks for your time.

[psfred]

The failure that causes the hard shifts is where the molded inserts tear loose so that the bolts aren't centered in the holes anymore, usually obvious because it's offset on way or the other. the colors on the driveshaft are factory, mine looks the same (quite a surprise, I'm used to plain black or rust!).

However, if the tranny is acting screwy and making noises, you are probably facing a swap. Best thing to do is to buy a rebuilt tranny and exchange, the chances of finding a tranny shop that can successfully rebuild a 722.x tranny is about nil.

I'll check with Hans for the outfit he uses, they seem to be very good.

Peter

[Kebowers]

these transmissions are not hard to rebuild, and wearing parts are cheap. It does take about 10 hours of 'on the bench' time to do it right if you are experienced.

All in all, the factory rebuilt exchange ones are a very fair price.