95 E300 Diesel hard shifting
 

I just bought a 95 E300 Diesel. 220k miles. Was shifting beautifully when I had the tensioner spring for the serpentine belt replaced. When I took it home it had a very hard shift to 2nd 3rd and 4th. A guy I work with suggested maybe the repair shop pulled loose a vacuum line. Is there anything up front they could have knocked loose to cause this hard shifting. If not what else could have caused it. I wanted to get some ideas before I hear back with the shops diagnosis.

Vacuum for the transmission might be sourced from a smaller nipple on the vacuum pump by the tensioner. I don't know what visibility is like under the intake manifold but there's a device hanging off the injection pump with a couple of vacuum lines. One line goes through a green cylinder to the transmission, the other finds its way to a vacuum source, either right at the pump or along the big hose to the brake booster.

Sixto
87 300D

There's a vacuum line connection directly by the top plastic mount for the tensioner spring, maybe check this to see if they disconnected it as the lines are kinda in the way when working on the tensioner spring.

Thanks guys! I took it in Saturday morning and the tensioning sprind was busted and the serpentine belt was loose. They replaced the tensioner spring. I bet you hit the nail on the head. I will definitely check it out and get back to you. By the way the shop, by the time I got done with the mercedes tech, had recommended a complete rebuild. But the owner of the shop drove the car with me and guaranteed that there was no need for the rebuild.

Same issue
 

I recently went through a similar issue- post repair of my belt tensioner shock I had hard shifting - mine was resolved by a breech in the vacuum under the air filter. I looked for a bad line but not under the air filter (not the little can shaped vacuum thingy either) I was told the air filter housing need to be removed to see these. Also check the lines by your TPS
Good luck it was aggregating

eng's rule of thumb

When vacuum issues come up right after a repair the first place to inspect are the vacuum lines that are close in the vicinity where the repair was made.

I looked at all the lines in front of the tensioner shock
 

But they were fine. Definitely vacuum related though - or a mule in the back seat kicking. Oddly these were not near the work area but they are 13 years old.

Btw- that's aggravating not aggregating in my post above

I found it. Geez what a dummy I am. That one was mercedes diesel 101 really. There are 2 vacuum lines right above the tensioner and one was cracked in half. I took a piece if tube and coupled them together at work and it fixed the problem, It's not perfect like it was so I will inspect the rest of the lines. On my behalf, I attribute my miss to the spinning head that comes with a $2000 diagnosis when you go in for a $100 repair. Great Job and thanks for the diagnosis.