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806 countershaft replacement


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Hi folks, just curious if anyone out there has info on this. I'm replacing my 806 countershaft with a left handed thread one.  Got the new one (used) in the mail today and noticed several differences between the old and new.   The part numbers cross referenced ok when I purchased. 

The new shaft is slightly longer,  has a groove in the middle,  the non threaded end is different and the threaded end doesn't have a slot for the washer locking tab. 

Is this going to cause issues?  Should I find a machinist to mill a slot out on the threaded end for the locking tab?

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25 minutes ago, randy hall said:

Hy-Capacity wants you to drill through the nut and shaft and install one eight inch roll pin.

I've used high strength locktight on those

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No matter which direction the nut screws on, I just put a tack weld on the nut and shaft.  That's what my friend who worked at IH through the 70's, 80's and 90's told me he did, so that's what I do.  I figured since he's put several hundred in and could do a TA job in less than 8 hours, I should take his advice.  I've only probably put in 10 TA's, but never had any issues.  If and when the next TA job comes due, grind the tack weld off, then weld it back in the same spot on the shaft.  If the nut gets too many spots on it, it's cheaper than a shaft. 

Incidentally the NV4500 New Venture transmissions had the same issues.  Right hand thread and the nut would unscrew.  I welded them in place too. 

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4 minutes ago, J-Mech said:

No matter which direction the nut screws on, I just put a tack weld on the nut and shaft.  That's what my friend who worked at IH through the 70's, 80's and 90's told me he did, so that's what I do.  I figured since he's put several hundred in and could do a TA job in less than 8 hours, I should take his advice.  I've only probably put in 10 TA's, but never had any issues.  If and when the next TA job comes due, grind the tack weld off, then weld it back in the same spot on the shaft.  If the nut gets too many spots on it, it's cheaper than a shaft. 

Thanks for the tip.  I don't need to worry about a washer behind the nut if it's a left hand thread shaft?

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4 minutes ago, AmateurHobbyFarmer said:

Thanks for the tip.  I don't need to worry about a washer behind the nut if it's a left hand thread shaft?

I would still put a washer behind it, but it would be fine without it. All you are doing with the nut is locking the shaft to the bearing. (By tightening down all the gears and shims assembled on the lower shaft.)   But the washer will keep the nut from scuffing the inner race of the bearing while tightening it down. It's not a bad thing to have it there. 

Incidentally, why are you changing the shaft anyway? 

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Some of the threads on the old one were mangled up when I removed the nut. 

Not sure exactly how it happened.  Either the threads were cross threaded during the install or some metal shavings from the roll pin got caught in the threads when I removed it. (First tried punching the old roll pin out but no luck, so I had to drill it out) 

I probably could have forced a nut back on the old shaft,  but that would've thrown torque specs off and I didn't want to play the guessing game. 

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34 minutes ago, pirlbeck said:

Correct me if I am wrong, but I think you need to use splined thrust washer #71147C2  with your new shaft. It is slipped on the shaft right after the shaft enters the front needle bearing.

I am fairly certain you are correct.  I vaguely recall that... and I found a note on ASAP saying that early 66 series and prior require the use of that spacer if using the new style shaft.  Been a long while since I had to put a new lower shaft in one.

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7 hours ago, J-Mech said:

I am fairly certain you are correct.  I vaguely recall that... and I found a note on ASAP saying that early 66 series and prior require the use of that spacer if using the new style shaft.  Been a long while since I had to put a new lower shaft in one.

I thought I better put it out there before the OP had the speed trans back together.

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6 minutes ago, pirlbeck said:

I thought I better put it out there before the OP had the speed trans back together.

I probably wouldn't have thought of that.  I remember the one shaft I replaced due to pitting on the front bearing surface, but I bought a new one and it came with the spacer (and nut) as I recall. 

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12 minutes ago, AmateurHobbyFarmer said:

Thanks for catching that!  So it would go where I circled in the image below?

That picture is misleading.  It would be the first thing installed on the shaft as you assemble it through the front bearing. Just as pirlbeck stated.

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