The Stovebolt Site Forums The Shop Area Engine Shop SM420 reassembly problems

Help!

I have gotten to the point of reassembling the 420. I have reinstalled countershaft, idler shaft and mainshaft (and all their gears). Now, when I reinstall the clutch shaft, everything goes in smooth (as per the manual) but when installed, the whole thing is locked and won't turn. I've tried shifting into neutral, different gears, nothing. It just sits there and won't turn.

Possibly I have frigged something up with the 3rd and 4th speed clutch hub and clutch keys? I've tried frigging around with them, but no joy.

I've completely gone back to scratch many times, all with the same result at the end. I've field stripped this *&^%$% thing so many times I think I can do it blind folded now. I just got so frustrated I was tempted to just beat the hell out it with the BFH (I'm not joking) so I quit for the evening. I'm getting tired of this.

Somebody please tell me what the hell I'm screwing up here? Or walk me through the clutch shaft reinstallation sequence because that's probably where I'm screwing it up.

Thanks,
John
Tell me again why I love old trucks????

Grand Pooh-Bah,

Had the same thing happen to me when I rebuilt my SM420. When you put the clutch shaft in, you had to hold the internal needle bearings in with the little ring clip. When you push the clutch shaft in, the other shaft pushes that retainer clip into a void in the clutch shaft. For some reason that seemed to hang up.

I took a small pipe wrench and put it on the clutch shaft, after I had the front input shaft plate bolted on, and gave it a turn clockwise. Next thing I know, the shaft is turning freely. Have not had any tranny problems in the running truck after doing that.

Just my opinion and any resemblence to the truth is purely coincidental.

BigMac

Thanks for the reply, Big Mac.

Are you saying, then, that once you had everything reassembled (like I have) and the tranny was locked (like mine), you essentially forced the clutch shaft to turn and that freed it up?

That's a gutsy step and I want to make sure I understand you correctly before I try it.

I can see where that roller bearing retainer clip might be a problem, but when I've disassembled the transmission on my previous attempts, I've noticed that it's been in it's proper post-assembly position (in the recess ahead of the roller bearings.

For whatever it's worth, I've reassembled my "bad" tranny, which is out of a '52, with no trouble and it works great.

So what's the prblem with running gears with a few pitted teeth? Will there be any other problem other than it will just be noisy in that gear?

Thanks,
John

Grand Pooh-Bah,

I had the same problem when I done my Trany.
I thought I installed all the pieces exactly the way they came out, but I was wrong. I flipped one set of gears and this made it inpossible to turn the rest, I do not remember which gear cluster it was but I think it was the set on the clutch shaft.