K4A-040 Transmission Slipping

[JPMOSE]

Hello,

My 280SE 3.5 (W111) has a strong running transmission, but it slips out of gear (ONLY WHEN ENGAGED IN 4th GEAR) when decelerating. It also does this when coming to a full stop. It only does this randomly. Additionally, I notice a shudder when accelerating on highway speeds (only in 4th gear).

If the lever is placed in "3", the transmission works perfect!

I changed the shifter bushings recently and the floor shifter aligns perfectly.

I changed the fluid with Valvoline Dex/Merc and MB filter. The old fluid was bright red with no brownish color at all. BUT...the old filter had black residue on the valve body side and at the bottom of the pan. Not a lot, and it was fine like powder. There wasn't any metallic residue. So it appears the fluid has been changed but perhaps the filter was reused. I also drained the Fluid Coupler. UPDATE: I had a helper that later disclosed there was a piece of metal in the pan at the front..I didn’t find this out at the time of my original posting.

The MB shop manual states 5.4 liters upon refill. I used this exact amount, but it barely registered on the dip stick. My 250SL has the same P/N for a dip stick, so I checked and they are identical. WHAT'S INTERESTING IS THE CAR SHIFTED PERFECTLY AND DIDN'T SLIP AT ALL! THE SHUDDER STILL EXISTED WHEN ACCELERATING (MODERATELY) IN 4TH ON THE HIGHWAY.

Since I verified that the dip stick was correct, I drove the car again (no issues) to heat up the fluid (drove 30 highway miles). Parked in the level garage and engaged all the gears. Then I added about 12-15 more ounces to bring it up to the full line on the dip stick.

Yesterday I drove the car and it jumped out of gear again!! This was the first time driving since I added fluid to the dip stick line. Everything returned as it was as mentioned in the first paragraph above!

I need to check the bushing on the throttle rod which connects to the right side of the transmission this weekend, as it may have a bad bushing there as well.

Any thoughts on what else to check? Thanks for your time!!

[JPMOSE]

I wanted to post an update. As it turns out there was a small piece of metal in the transmission oil pan. It was curved and was made of steel. The K3 band had a piece break off of it. If you look at the shape of the band, it narrows to what looks like a strap or the connecting point between the two wide bands. It appears that the strap broke and therefore the band was not held tightly. This is why it would slip out of fourth gear when you let up on the gas. They’re just wasn’t enough pressure to hold the clutch pack real tight. As a result, I remove the transmission with the help of an expert, and shipped it off to Sun Valley transmissions. They have a stellar reputation for rebuilding Mercedes transmissions. The cause was likely just age and fatigue. The transmission has always been treated well… But sometimes things just happen with age. I’m looking forward to a new rebuilt transmission that will last for years and certainly outlive me!