300TE transmission query - PeachParts Mercedes-Benz Forum

adrianruk · #1 07-22-2002, 07:02 PM

A few weeks ago I bought a '90 300TE with 192000m. I failed to check the transmission oil before purchase - a bad mistake. When I did check I found it was full of emulsified oil. I drained it, changed the filter & refilled it with Dexron II. I ran the car for a couple of days then drained & refilled the oil. Until then the trans had been working fine. Now its OK when the car is cool but when hot the changes up and down are very sharp and the gears engage with a hard clunk. Also, when I put it in reverse there is a lot of resistance, almost as though the brakes are on and I have to give it a lot of throttle just to get it to move. If I leave it for 10 mins or so to cool down every thing is fine again - until it warms up.
I have today drained the oil and found it clean but it had changed colour from pink to a dark reddish brown. I had the rear casing off to change the speedo drive gear which broke a week or so ago (don't know if this was related or just coincidence!). Everything visible appeared fine.
The car had new coolant pipes fitted 9 months ago and has recently had a new radiator fitted ( don't know exactly when).
Any help would be gratefully received.
It has a 722/3 transmission.
I'm trying to avoid having to fit a rebuilt unit
I am toying with fitting a secondary oil cooler since the box seems fine at lower temperatures. Or perhaps I should add some water to the oil since it was OK before I changed it!!!
My '87 300TE is still going strong at 265000m & has caused me hardly any problems in the 4 yrs and 140000 since I bought it. Perhaps I should keep it & sell the new one.
Adrian
PS I'm also having uneven idle/stalling problems which I'm working my way through the archives for the solution.

psfred · #2 07-22-2002, 09:01 PM

Bad news, water in the tranny fluid. It ruins the frictions, since they are usually paper-like material (MB may use semi-metallic). It will also cause corrosion of valves, drums, gears, spacers, etc and cause all sorts of operational problems.

I would guess you are having serious slipping frictions problems if the oil is burning so fast -- you will not be able to fix that without a rebuild, as the friction material is all gone.

I assume you checked the pan for crud when you changed the oil -- what was in there? If nothing, or metal shavings, the tranny is toast, since you should always find some black powder from the frictions and steel disks. Nothing would indicate that the fluid was changed very recently, and metal particles indicate that all of the frictions are gone.

Peter

joe p · #3 07-23-2002, 07:28 AM

99% of auto trannys use a waterbased adhesive to hold the friction material on the clutches and bands together. The good news is that stuff is fairly cheap. The bad news...... its fatal. The only real fix for this is overhaul. The water in the ATF attacks the glue and off comes the material.

Joe

stevebfl · #4 07-23-2002, 08:32 AM

Don't be hasty, if you aren't getting clutch material into the pan I would surely wait for it.

Lacking clutch or band material won't make it shift hard unless the pieces screw with the control function of valve body. They would have the opposite mechanical effect.

adrianruk · #5 07-23-2002, 07:05 PM

Many thanks for the info all, even though as I suspected it was not what I was hoping to hear!
The oil I drained from the sump originally contained no metal particles - the pan was quite clean as I recall, though there was a slight sludgy residue. Much the same as I have previously found in my other merc boxes apart from the emulsified oil. I have not found any metal or other particles in any of the 20 odd litres I have drained from it.
I contacted the previous owner today and discovered that the new radiator was fitted the day I collected the car! When I agreed to buy the car the a/c was not working and he sent it in to the garage which has maintained it (at great expense to him!) for the last 2 years. He was told that the condenser was holed and the repair would cost him £230. He picked the car up from them just before I collected it. When he got the bill in it was for £450 and included the new radiator, with no explanation. He has not paid the bill and is waiting for them to account for the new rad. He is recontacting them tomorrow and should be able to give me the full service history for the last 2 years. He assures me that he had no problems with the trans at all and it certainly worked fine on my 30 mile test drive. He is a genuine sort of guy & I believe him. In fact the problems only occurred after I changed the oil, some 2200 miles ago now.
I will post again tomorrow when I have the full story.
Thanks again
Adrian

adrianruk · #6 07-25-2002, 06:41 PM

I'm still waiting for the history from the garage, but I'm told the trans oil had not been changed for some considerable time. I've pulled apart the filter I removed originally and found a few black bits & a few metal particles in the filter medium when flattened out - not enough to cover a small fingernail in total.
I'm almost resigned to having the box rebuilt, though it doesn't seem to be getting any worse. Is this a job I could undertake myself? I've never attempted an auto box before, though I have rebuilt manuals & plenty of engines.
As a desperate measure I'm thinking of trying a Dexron III fluid (instead of the cheap Dexron II I've always used) & a gearbox conditioner additive. Is this worth a try?
Adrian

stevebfl · #7 07-26-2002, 08:33 AM

I always say: "If it ain't broke, Don't fix it". Since you are obviously sensitive to its performance, I wouldn't do anything until it changes performance. Pay close attention to reverse gear; back it up a hill. If its tight , drive the car.

If you wish a project go here: http://www.transonline.com/electroPublisher/website/index.cfm?pageID=2889#

adrianruk · #8 08-02-2002, 06:42 PM

Tried changing the oil for Dexron III - no improvement. I now find that when it's hot it pulls forward strongly when in neutral (much more than in D) and it's very reluctant to go backwards at all. I won't use the car any more if I'm likely to meet heavy traffic.
The box has to come out.
I'm considering fitting a secondhand transmission while I rebuild the duff one but am having trouble finding one with the same number as mine (722 359). I know the last 2 digits identify the model & year but is there a chart somewhere that would identify which box fitted which car? Mine is a 300TE 24, M104 engine, 3 litre 24 valve, with variable valve timing and no catalytic converter (230bhp compared with the 188bhp from the M103 version sold here). I therefore don't want a transmission from a 250D!
Adrian
PS This engine had a head gasket go last year at 175000m