Hey guys,

I have an '85 300TDT which has been knocking in the rear of late. Car starts up and runs fine for a while and then the knocking begins (knock is definitely speed related - ie knock frequency goes up with speed). Seems like it's drivetrain related but can't pinpoint a halfshaft. Could be driveshaft into diff.. But why should it run fine for a while and then start knocking ? Did see some gear oil leak (and another fluid - not brake fluid !), could this be the culprit ?

By the way, what repair manuals do you use ? I don't have one, would prefer a factory manual in book form

Thanks,
Bhima

Leak is likely hydraulic fluid from the hydropneumatic suspension.
Mine knocked like that when the axles were dry. It sounded like a helicopter was hovering above the car, particularly when going downhill and backing off on the accelerator enough to unload the drivetrain. Lubricating the axles fixed it.

__________________
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

You can look for the manuals on eBay and post a request in the parts forum on this site. In the meantime, you can order the CD Manual from the Classic Center at MB USA for $20.

Here's a direct link, just enter the details of your vehicle in the left margin and it will show the CD manual for your car:
http://www.classictechlit.mbusa.com/MB/Default.asp?cookie%5Ftest=1

You'll want to order the "Model 123 Service Manual Library"

__________________
Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

I had a similar noise in my 81 300td, it turned out that I was missing one or both rubber muffler hangers in the rear of the exhaust.

Hey thanks guys !

It's not dampers on the exhaust.

Kerry, you're right on re the hydraulic leak.

By the way, how did you lubricate the axles ? Are you referring to lubing the U-joints (inside the boots) or topping up the gear oil or ..?

Cheers,
Bhima

Local indy lubricated the axles by putting some kind of grease inside the axle boots.

__________________
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

More research and peering at the half shafts.. Since I will be doing the job myself and I'm on a tight budget, it looks like my best option is not to mess around with the leaking (apparently the boots did have gear oil in them) CV boots, but just replace the entire half shaft. Do you guys have any experience of doing this job ? Looks straightforward upto a point (I might need a special tool to get it off the diff and/or the hub)...

Cheers,
Bhima

Oh never mind.. I found a superb writeup with pics in the ShopDIY section.

Thanks,
Bhima