I finished rebuilding my 1983 240D Manual Transmission--I had tore it down because I couldnt find a new used unit, and my existing unit could not downshift from 4th to 3rd Gear and often missed 3rd gear. I think I damaged it because for 2 years I used 90W gear oil in it vice ATF
When I opened it I found everything in very clean shape except that the third gear synchro Spring had come looose and had been digested by the transmission.
I rebuilt it carefully with a Beginners Luck. I replaced all the Bearings, Synchros and Synchro springs and most of the snap Rings..
I replaced it in the car last Sunday and with a Huge Gasp, put the car in gear and was pleasnatly surprised to see it worked perfectly and could downshift from Fourt to Third Gear!

The only thing WRONG is that sometimes, in third gear, the transmission will pop out of gear into neutral. Also with the Clutch engaged and at a Full Stop in while in 3rd Gear, I will hear a rattling/whirring noise.

In all honesty I think I rebuilt the transmission very well. By saying that, I mean you can only put it back together correctly, and well (it works), or incorrrectly ( it doesnt work). I got Lucky. So I dont think the problem is the Transmission.

The Linkages have been adjsuted carefully, so the only other place I can look is the pressure plate or throw-out bearing. Can anyone diagnose these Third gear problems?


83 240D Manual Trans rebuild--I finished it, but something is wierd about 3 rd Gear..

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What did you use in terms of information about clearances.... and what kind of special tools did you need ?
Are you saying you don't think that the jumping out of 3rd is due to something inside the transmission ?
How much did the parts cost you ?
Place the trans in neutral and let out the clutch.. does that end the whirring noise ?

I would guess, and this is only a guess, that there is more wrong with 3rd than just the synchro spring. Constant mesh transmissions aren't supposed to allow any pressure to be transmitted from the gearset to the shifter, so I would surmise (and I'm NOT speaking from experience here!!) that either the dog clutch or bearings are bad, causing some rotational energy to be transmitted to the shift fork.

A rattle or whine with the clutch in cannot be the gear set -- it's stationary with the car standing still. If it rattles while rolling with the clutch in, I'd personally think bearings. Otherwise, think loose bushing somewhere in the shifter mechanism, probably the top part where the shift lever goes.

My old VW as bad about popping out of 1st -- needless to say the synchros were pretty much gone by then.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Well, I'll cast my vote for the tranny being good. You say the linkages are adjusted properly, but I'll say start there AGAIN starting at the rubber bushing inside the shifter and re-adjust the bars (to make sure it's going FULLY into 3rd.)

The sound with the clutch in is the throw-out, if it happens only in 3rd, then again, I think there's something weird with the linkage not quite getting 3rd seated.

Check if the sound is the same in 3rd with the clutch in as it is in neutral with the clutch in.

Also, could be the new spring for the 3rd synchro is stiff, AFTER re-adjusting the linkage, drive it for a while and get everything good and hot. Might "fix" the problem.

Good luck, I suspect I'll be in this same place very soon with mine!

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1984 300D Turbo - 4-speed manual conversion, mid-level resto

1983 300D - parts car

1979 300TD Auto - Parts car.

1985 300D Auto - Wrecked/Parts.


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"If you don't know where you are going, any road will get you there". Lewis Carrol

Please look at the DOGS. I know there is a problem somewhere...

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This ought to really confuse the discussion. I have a 78 240D with a four speed. When I bought it from a friend of mine, he warned me that it popped out of fourth, unless you keep your foot on the gas. Which it does.

Thinking about a temporary solution, I decided to turn up the idle adjustment screw whenever I got out on the open road and wanted to go above 50. Sure enough, that stops it from popping out of fourth. Also, using BP premium diesel makes the engine run much smoother, and this also helps.

Looking through the service records, I noticed that the transmission and differential oils have never been changed. I am going to change both today (Redline MTL or Mobil 1 ATF for the trans), and Synthetic 75W-90. I figure this will either make the problem better or worse. I'll let you know.

Failed or worn pilot bushing/bearings (the one in the end of the crank) can cause the transmission to jump out of gear. Excessive wear in the input shaft bearing (the one in the front of the gear case) can do the same thing too.

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Never a dull moment at Berry Hill Farm.

Is there anything different about changing diff/tranny oils in a Mercedes compared to other autos? Other than the fact that it was one of the few cars that it takes ATF in the MT?

One more time...
(I'm debating doing something like this myself soon...)

How much did you spend on parts ? (approx)

-John

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2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

I know should probably start a new thread for this (a cross-thread? ha-ha), but what size hex wrench is needed for the fill and drain plugs on the tranny/diff? Also, where does that line go that runs from the transmission and dead ends at the firewall on the driver's side?

I think a service manual is in my future. Which one is best?

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'Plan A is @#$%'d up. You got a Plan B?'
'This is Plan B!'