Can someone please confer that the difefrential fluid on a 1984 300DT should be changed at every 90K miles. I can't find this info on the maintenance schedule manual. Thanks.

Can't speak for the actual official maintenance interval, but I plan on changing the fluid every 30K miles with Mobil1 gear oil (I think it's like 75/90).

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Put 75w90 Full Synthetic Castrol
Its the best for diffs

Thats what i run and no problems after i rebuilt my diff, sometimes the original stuff they recommend is too old

The interval is 30Kmi. Replace with GL-5 fluid. MB does not approve synthetics for rear diffs so I use whatever mineral oil Wal Mart has - either Valvoline 80w-90 or Castrol 80w-90 for $2.94 / qt. Many use synthetic with no problems. Be sure to remove the fill plug before the drain plug in case its stuck!

__________________
Brian Toscano

Thank you for the information . I will be doing a change soon.

How difficult is that job? Also, I see oil dripping from mine. Is that an O ring seal and is that an easy fix or better left to my mechanic? Thanks.

__________________
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

On mine, the seal was just with RTV...

I put Royal Purple 75W-90 oil in...would have used Redline if I could have found it, though, although RP's good stuff.

It's pretty easy; I did mine as part of doing the axleshafts.