If you are sure the howling isnt caused by something else it would probably cost about $20 to change the Differential fluid to Mercedes Spec and it will last a long long time with no headaches.

My contact at the oil analysis place I've used says 75k for dino, 150k for synthetic.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

That I'm not 100% sure on. I know that it only howls on deceleration. I don't recall ever hearing it howl on acceleration.

You wouldn't happen to have a part number for the MB fluid?

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

I'm fairly certain the only cars I've ever changed the diff oil on was my gold 300SD and the 190E. The other three I've never done.

I am wondering if it might be time. Maybe I'll do the 190's with the MB fluid and see if the howling goes away. That would at least tell me if the howling is in the gears or the oil. If it does cure the howling, i'll just use the same spec fluid on the others.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Part numbers for fluids can be found here:

https://bevo.mercedes-benz.com/bevolisten/bevo-sheets-sort1.html

The hypoid gear oil for cars is usually sheet 235.0:
https://bevo.mercedes-benz.com/bevolisten/235.0_en.html

The listed part number is A0009892803 in the 85W-90 weight, although many other oils from different manufacturers also comply.