Unusual speedo drive problem

[Panshovevo]

I can't keep a speedo drive in my 4 speed tranny. It strips the fiber gear within a tenth of a mile or so. I first drained the tranny, stuck a borescope down the drive hole, and counted the teeth on the drive gear. It has the proper number of teeth. When I pulled the tranny out recently, I first noticed that the upper left corner of the case had been broken and welded. When I pulled the top cover and inserted a new drive unit, it appeared to engage, but if you try to turn it backwards, it binds. It looks like the engagement is inadequate.
Any suggestions, other than another case?
Regards,
John

[RUBONE]

The spiral gear in the box is a press fit on the countershaft cluster. It is centered on the cluster boss when originally fitted. Is yours? Or has it been moved off center at some point. And are you sure on the tooth count? There are three different sets.
Robbie

[Panshovevo]

The spiral gear in the box is a press fit on the countershaft cluster. It is centered on the cluster boss when originally fitted. Is yours? Or has it been moved off center at some point. And are you sure on the tooth count? There are three different sets.
Robbie

Thanks for the response, Robbie.
I am certain of the tooth count, checked it around 10 times to be sure.
I'll look tomorrow, to see if I can tell if the drive gear is centered on the boss.
I forgot to mention that the countershaft has some excess end play, around .030" overall.

[Bosheff]

Is the .030" end play clerance above and beyond the service spec max?....bosheff

[Panshovevo]

Is the .030" end play clerance above and beyond the service spec max?....bosheff

No, that is total end play. I think the spec is .012 max.

[Bosheff]

If yer speedo drive gear is not centered properly on the countershaft, AND yer .018" or more past the service limit of the countershaft end play, I'd think that would be more than enough to cause the problem you are having....bosheff

[Panshovevo]

If yer speedo drive gear is not centered properly on the countershaft, AND yer .018" or more past the service limit of the countershaft end play, I'd think that would be more than enough to cause the problem you are having....bosheff

Thanks Bosheff, I'll check that today. Was going to do it yesterday, and as so often happens, I walked into the shop with one thing on my mind, and got distracted by a dozen other things. At least I don't get bored...