Dana 18 Output Gear Loose

I was in the process of installing the AA tapered bearing intermediate shaft in my 1969 CJ5 (225, T14) when I noticed that the output gear seems to be very loose on the output shaft!

Video

I can't seem to find where anyone else has documented such an issue. What would cause this? Any guesses as to whether it is the gear bore, shaft, or both that are causing the issue?

I rebuilt this transfer case maybe 30k miles ago, and had no issues until recently it started to whine more, which prompted the tapered bearing conversion. For whatever its worth, the shaft and needle bearings looked okay but the intermediate gear bore didn't look good. At the time of rebuild, the intermediate gear had some pitting but much less. Everything else looked good. I have never noticed any metal in the oil.

 

I believe that is called brineling. Don’t know if it’s caused excess tolerances or wear.

 

If that intermediate gear had some pitting when you assembled it, I would have expected it to look much worse after 30,000 miles. Those needle bearings need to have both the gear's bore and the shaft in perfect condition. Less than perfect will chew things up. Your intermediate gear is probably a good candidate to bore out (Mcruff?) for taper roller bearings.
You have something very worn with that gear wobbling. That was likely making some loud whine. Looks like a teardown is in order to see whats making things so loose.
-Donny

 

That ridge between the rollers looks to be .020-.030, maybe more. With that much slop, the intermediate gear can run cocked and you should probably check the output shaft gear for abnormal wear. As Donny's comment, the intermediate gear should be fine with the tapered roller conversion.

 

To clarify, the gear bore shown is the intermediate gear after the 30K miles. At the time of rebuild, the pitting was minor - just noticable. I suspected that to be the source of the additional whine that recently started, so I had it bored and installed the tapered bearing kit.

During the installation I noticed the looseness of the other gear, which I can't make much sense of. How could it get so loose? It doesn't seem like that should be a high wear area, especially since there is no relative motion between that gear and the shaft in high range.

 

That other gear is what I referenced above. If the intermediate gear is running at an angle to it's axis, it puts an angled load on the output gear which in turn, makes it wear crooked on the rear output shaft. In the extereme case, you trash that gear, the rear output shaft and the sliding gear.

 

That makes sense. I think the ridge looks a bit worse in the photo than in real life though - the play in the intermediate gear was only barely perceptible. The play in the output gear on the other hand... I am not sure how much intermediate gear misalignment it would take to mess up the output. The gear teeth don't look unusually worn to me, but I will get a much closer look once I have them out on the workbench.

So does anyone have the spec for the output shaft OD and output gear ID? I'll be taking it apart to inspect soon. I'll probably pull the necessary parts from my spare D18, and so I want to make sure those are in spec too.

 

New rear output shaft diameter where the output shaft gear rides is about 1.314". There should be no step in the shaft where the output shaft gear rides. Debella has B&L/Spicer NOS front and rear output shafts but if you have multiple parts that need replaced, it's going to be a lot cheaper to just find another servicable complete transfercase.

 

I think that if the snap ring was missing, the preload could not be set correctly, right? If the thrust washer was missing hat would certainly create some play. I'll find out soon. Either way though, the gear seems much too loose on the shaft.

Could excessive wear in the output shaft's internal bushing cause enough misalignment to wear out the output gear?

 

The rear output shaft is supported by the tapered roller bearings on both ends so that should not in any way be a factor. The only real problem I can think of is if that pilot bushing had a lot of wear it would likely cause premature failure of the front output seal because it would allow some small angle on the front output shaft.

It is often discussed that front lockout hubs can cause upper kingpin lubrication problems. I have always thought the additional wear on that front output shaft pilot bushing was more of a problem. With no lockout hubs, the front output shaft is always turning close to the same rpm as the rear output but with the hubs disengaged, that difference is 100%.

 

The shaft and gear are out. The first thing I noticed was that even with the thrust washer in place, there is a sizable gap between it and the snap ring (not in this picture but you can see where it would go), allowing the gear to move axially. Is this normal?



Clearly the shaft is worn and there is a significant shoulder. For fun, I measured 1.289" at the shoulder and 1.305" at the other end near the sliding gear splines.



The gear has some wear markings, but they don't hang a fingernail or anything. I measured its ID at 1.320". Not sure if this is acceptable but I will be replacing it.

 

My NOS output shaft and gear have arrived. Still wondering if the gap between the thrust washer and snap ring (shown in the first photo of my last post) is acceptable? The gap is 0.022".