85 big red 250es transmission skipping

[BigRedNB]

Hey guys I'm new to the forum, been visiting it for quite a while now lots of good info on here.

Having a weird problem with my 85 250es. I just bought a complete used engine for a good price and dropped it in as the original was clapped out. The engine runs the very best, no smoke at all, and the clutch grabs well and the shifter feels like it should, but the transmission is doing something very strange. It started out doing it only in 1st gear, but after several miles has moved into doing it in 2nd and 3rd gear now too (once you get up into 4th and 5th it runs along just fine). So what's happening is it sounds like it's between two gears when you go to take off from idle. You can hear a gear grinding noise coming from the right side cover. Once you get rolling, it starts to go away. Let off the throttle and hit decel then back on the throttle, it'll do it again. The rear end is in good shape I thought maybe it was skipping back there but it's 100% an issue in the clutch side of the engine. There is fairly new looking gasket maker on the right side cover, so someone had been into it in the last while. I'm wondering if maybe something is out of adjustment or if they put something together wrong. Anyone ever experience this?

Thanks

[HoldMyBeer]

Have you had any break throughs with this one? I’m not full of great ideas for this one, I don’t do bottom end. Guess I’d start by taking that side cover off and checking everything you can see. If it comes to splitting cases I’m out.

[gimmeamidget]

The engine mount spacers are different sizes. If you get them wrong your engine won’t fit correct and can cause this? Check if it looks aligned or if it looks less than an inch off. You may need to swap spacers.

[BigRedNB]

Thanks fellas, I will have a look at the spacers in the morning. I have been debating digging into the clutch side cover to see if I can find anything that looks wrong, just haven't had a whole lot of time to work on it lately

[BigRedNB]

Well I had a look at the spacers, the engine doesn't appear to be out of alignment. Might have to dig into it.