Kreuzfeuer

Over the past few weeks, I've noticed a weird occurrence while shifting from 4th to 5th during aggressive driving. All other shifts are as smooth as the MB gearbox will allow, but the 4-5 upshift has been almost a "grind" as if you let the clutch out too early before plugging into the gear. The gear grabs, and I don't miss the shift, but you hear it grind for a split-second and can clearly feel it in the shifter.

If you wait a half-second between the 4-5 shift and gently push the shifter into 5th, no crunch. 5-6 upshift, even when under full acceleration, is smooth. It's just when you're shifting aggressively that the "crunch" for lack of a better term, is felt.

What is this a symptom of? The clutch feels nice and firm, and no other shifts are affected. Bad synchros?

I will be doing a fluid flush and refill with the OEM Mercedes fluid required. The transmission has 57,000 miles on it.

Thank you for any help,

Ausmbtech

Very unusual on such a low milage transmission but I have seen this on high milage sprinters and vito which use the same transmission.

These boxes have double and even tripple syncros on the 1st and 2nd gears, doubles on the 3rd/4th and singles on the upper gears. Therefore the upper gears show the wear first.

Try changing the oil first, but if it's consistantly in 5th gear only (4-5 upshift and 6-5 downshift) then I'd say the syncro is worn

Kreuzfeuer

Thank you for the response! Yes, the gear-clash only occurs from 4-5 and ONLY when driving aggressively. Downshifting from 6th to 5th is smooth as silk, both during aggressive driving and normal. If I'm driving normally, the 4-5 shift is smooth.

I am going to try using Redline MTL, I've seen numerous posts about that fluid improving the shift feel of the MB transmission.

If that doesn't cure it, I'll have to get the 5th gear synchro repaired. $$$$$