TMCC consist question, please help

From my experience, and what others have told me, TMCC or Legacy steam and diesels do not mate up in a lash-up. The gearing is totally different. I played around with a Legacy UP E7 and my Legacy 4-8-4. Never got them to sync. 

What I do when building a lash-up, I place the engines on the track about 1 to 2 feet apart. Once the lash-up is made, I then run them to insure that both are in sync, and that one does not move faster or slower than the other. 

If they all run in sync, then I know I can couple them up and run 'em.

RAY

First off, if you have similar engines, there's a couple of rules.

You MUST run the consist in TMCC mode as it can't be configured with a Legacy as the lead.

You'll likely have to turn cruise off of at least the TMCC engine, that gives it a lot of "slop" to deal with speed differences.

Although GRJ's answer is not "Long-winded", it answers your question in a Nut Shell.  GRJ always comes from a reference of Vast Knowledge of our Hobby.