Hello.
I bought a Mercedes 190D 1 month and a half ago and I have been putting all my effort to put it back to its original standards. Couple days ago the transmission was rebuilt by a friend and I. Before that was done I had lots of problems when shifting.. early shifting on it, and it still does it.. When you are rolling at 20MPH it's on the 3rd gear already.. by the way.. the 4th gear doesn't works?.. or I think so.. since I haven't noticed when it shifts to 4th..

The transmission work was pretty good repaired, my friend is a transmission mechanic. I've read on this site regarding the vacuum.. vacuum could be all the problem. I tried to adjust the Vacuum Modulator but it just makes a little bit late shift, not as should be, and the transmission kicks (when upshifting).
I don't really know how to start checking.. how can I test if the vacuum pump is working. Oh.. I disconnected the vacuum that goes to the valve where the air cleaner goes and it's a good vaccum pressure.. What else should I do to check..

I hopw you guys can help me out.
Thank you so much.