'87 300TD Transmission - PeachParts Mercedes-Benz Forum

nyc10009 · #1 01-19-2011, 12:05 PM

Hello everyone. It's been a while since I posted; my beloved '87 300TD is nearing rebirth from the paint shop soon.

Meanwhile, a friend had a local independant MB mechanic swap a complete engine & trans from an '87 300TD into an '87 300D (sedan). The trans isn't shifting or working very well. It worked fine when it was in the wagon. The mechanic (12yr MB, factroy-trained) says its because the wagon trans is different. I know the wagon has the same trans as the S-classs, but shouldn't it work OK in the sedan? This doesn't sound right to me.

Anyone with thoughts on this, before I challenge this mechanic--very much appreciated! Will

vstech · #2 01-19-2011, 12:07 PM

I'd call roy for specifics. I am unaware of any differences between the two cars. TD and D in 87 should use same transmission and shifting points...

mbdoc · #3 01-19-2011, 12:31 PM

The W124 sedan (124.133) & T124 wagon (124.193) both use the same trans (722.317),
MB part number 124-270-00-01.

The W126.125 300SDL does use a different trans due to the electronic speedo.

retmil46 · #4 01-19-2011, 07:38 PM

Could be it's not anything wrong with the engine or tranny itself - but perhaps old original leaky vacuum lines, misadjusted throttle cable, etc, that were already on the sedan.

When I got my first 87, it had the infamous "mule kicking the rear bumper" hard shift at anything other than WOT. It was a long process, first chasing down all the vacuum leaks due to cracked hard lines and ancient brittle rubber hose. Then doing the tests in the FSM and discovering the vacuum control valve was long gone and required replacement, plus checking the vacuum at other points and the final vacuum signal to the tranny. After that came adjusting the throttle cable and the throttle linkages, plus the feedback cable from the trans. And the final piece of the puzzle was having the tranny pulled out and all those 20 year old leaking seals replaced. At the end, I had a properly shifting tranny and a car that would run like a scalded ape.

That's another possibility - if the tranny hasn't had the seals replaced in some time (or never), especially around the oil pump, it could be that something got "disturbed" during the transplant process , and some seals, either vacuum or hydraulic, aren't doing their job any more.

FWIW, my tranny guru of over 12 years back in NC says these particular trannys are IHHO the toughest auto trannys ever made. When I asked about getting the tranny I mentioned above rebuilt, convinced there was something significantly wrong with it, he declined - he said at most, it would just need to be disassembled and have all the seals replaced, then properly adjusted - that it was rare indeed to find something mechanically wrong with one of them, unless it had been badly abused. Turns out he was spot on.

babymog · #5 01-19-2011, 07:57 PM

This "Mechanic" is incorrect. If it were different (which it isn't), and incompatible, why would he have made the swap?

A good Mechanic knows that proper adjustments and a healthy vacuum system are extremely important in the installation of an automatic transmission, he's just ducking his responsibility to get it right.

Don't pay until it's right.

vstech · #6 01-19-2011, 10:36 PM

and don't let him keep the original transmission... there's likely nothing wrong with it.

jonbobshinigin · #7 01-19-2011, 11:12 PM

I'm at a similar situation where I think I need my tranny rebuilt. Either way mine needs to come out for thr front pump seal, which is leaking. When I first got the car and knew nothing of the vacuum system, I read about the modulator valve and adjusted it WAY soft and drove it that way for several thousand miles. The car had probably 160k on it when did this and a tranny service was done around this time, including draining torque converter.

Eventually I resolved the vacuum leak and adjusted transmission at least close to what it should be. Might I have damaged or worn thr transmission out when I did this?

As the OP is having issues and may have to yank the tranny again, what seals, pistons, or parts are user replaceable without rebuilding the entire trans?

I am thinking may pull mine, install the spring kit and update some of the parts that had known "updates" or replacements. Does anyone have a list of these?