1985 300D

There is a rhythmic thumping/knocking sound coming, I believe, from the area of the transmission. It is really audible inside the car, less so when looking under the car. In the car it is difficult to pinpoint as it seems to move around depending on where my head is at, however I'm pretty sure it is strongest around the transmission hump in the car.

Here are a few other details:

• The noise seems worst/loudest in the morning.
• Doesn't seem to affect driving of the car.
• Once the car is warm the sound becomes either inconsistent much quieter so that I only notice it sometimes.
• The speed of the sound increases with engine speed regardless of whether I am in gear and moving or out of gear in standing still.
• Transmission mount should be replaced but isn't in terrible condition.

Is there any reason the auto transmission might be making a thumping noise?

Any other things I should check?

thanks

Check your flexdiscs and center bearing

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Thanks, yeah I did that and, while the should be replaced, I don't think they are causing the noise. The sound is present when I am in park and the driveshaft isn't spinning.

Perhaps something got lodged in the torque converter and is spinning around. I would try inspecting the torque converter while someone is turning the engine over manually with a wrench on the power steering pulley nut. Check your transmission fluid. If the plug on the torque converter got loose by any chance you may have leaked fluid and this would be an indication of the problem. Any red fluid on the ground or on the tranny case?

Richard

__________________
85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

Check your vibration damper on the front of the engine...

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I'm not leaking any fluid, in fact it looks like the PO may have overfilled the transmission a bit.

I would like to inspect the flex plate, but have been unable to find a good how-to using search. Can anyone point me to some good info on inspecting the flex plate/torque convertor?

There's a little cover right under the engine between the block and the adapter plate. If you remove that you'll be able to see the flywheel teeth. If you turn the crankshaft by hand you can spin everything round until you see the bolts that go through the flex plate into the torque converter. There are 3 sets of two.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

How are you checking trans fluid level.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

dipstick

Transmission warm, engine running?

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

1.On Absolutely Level Ground/Pad ?
2.With The Fluid @ Operating Temperature ?
(That's 20 minutes of Driving [Mixed] City/Highway, so the Fluid is Warmed!!!)
3.Let it Idle in Park for 4 Minutes.
4.Remove Dipstick and Clean (NOT WITH A Paper cloth! Use Leather)
5.Insert Dipstick and check the ATF level.

__________________
'84 300SD sold
124.128

Any no lint paper works fine. I find used receipts work well. Or even just a random sheet of clean paper.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Good stuff, i'll give that a try this evening. Thanks.

Coffee filters should be OK. They are more flexible than paper. They were recommended in my computer manual for cleaning off the processor and heat sink where a lint free environment is needed.

__________________
85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

Followed this procedure this evening, fluid level looks just right. Thanks for wisdom.