M151-A1 Transmission problem

I just received a 1966 M151-A1. The transmission will not go into second gear. All other gears are not a problem. No raking or grinding occurs when shifting into any gear except second. It grinds and will not engage. The previous owner replaced the top cover suspecting that possibly a fork was bent, but that did not correct the problem.

Any ideas?

The grinding sounds like the syncos are worn out and not matching rotating speeds for a smooth engagement. If that is the case double clutching should allow it to go into second. Try the semi-truck shifting method and see if it will go in. Shift into neutral from first, release the clutch and let the engine RPMs slow down and put light pressure on the shift lever. You can feel the teeth rubbing and tell if you ned to speed the engine up or slow down more and should find a spot where the trans will slip into second. If this does not work then I don't have a clue what could be wrong. By the way, can you put the trans in second with the engine not running??? If you can then my first comments are correct.

Thanks Pop, I own a WC-54, so I'm quite familiar with double clutching. I tried double clutching the Mutt today and it still popped right out of 2nd. I also tried just putting it in second gear without anything moving. No go! It wouldn't stay in gear even with the engine not running. I decided to take it for a drive to keep it limbered up and the batteries charged. I put it in reverse, backed up about 10 feet, put it in first to pull forward to head down my driveway and it acted like it was hung up in reverse and 1st gear (brake was definitely off). The Mutt wouldn't budge, engine stalled. I kept trying other gears and reverse again, still no go. I kept moving the gear shift lever, which felt really sloppy, and finally put it in each gear, then started the engine put it in first and it pulled just fine. I pulled it back in front of my shop and left it be. Something is way out of sync somewhere.

You will be pulling the trans out for repair. Sounds like the rear mainshaft bearing may be done in causing the mainshaft to move, it does'nt sound like a fork issue. Just hope the syncro, slider, and gear are still good.
Post up some images when you get it apart, it is a very simple trans.
Bearings are common numbers.
Really, the job is not as bad as it sounds

Your best bet is probably to get another transmission. That will be cheaper in the long run most likely. I got one for my Mutt several years ago for $100.00. If you were closer I have two transmissioms that could have the parts you need. The one in my Mutt was apart in a bucket when I bought it. The other one is on an engine I bought for parts and water had gotten into it and ruined it, but it does have some usable parts in it.