Speedometer Adapter Leaking Gear Oil

[Valence]

A little follow up:

So after a little more than 1 year and (guessing) ~800 miles in my deuce, I pulled out the stock speedometer adapter to put in a 1:200 ratio adapter.

Immediately it can be noticed that gear oil was fouling the grease in the speedometer adapter - this means that the replacement seal failed.




Upon closer inspection I was able to determine the culprit:
The inner spring on the new Viton seal had partially come out. The spring also wore a groove into the spindle of the shaft that goes into the transfer case.




Attempting to avoid repeating this again I put in a new, exact same Viton seal (thanks to bonedoc!), but this time I put it in the opposite direction. I'm not sure if this is correct or not but the previous orientation already proved problematic. My hopes here is that the spring won't come out again as it'll be against the, relatively, flat surface face of the inside of the speedometer adapter.

But I worry that the worn groove in the shaft will find a lip of the seal and still allow gear oil through, but I'm hoping for the best as the oil seal is double lipped.




Here's a comparison of the stock 1:187 adapter on the left and the 1:200 adapter on the right. As can be seen, the speedometer cable threaded adapter wasn't needed, but I did have to reuse the shaft assembly that threads into the transfer case.

 

[Valence]

Due to the design of the 1:200 adapter, I wasn't able to keep the same orientation of the adapter on my transfer case

As can be seen below, if left this way you would be unable to access the grease zerk. So I rerouted my speedometer cable over top of my transmission and down the passenger frame rail (not pictured) so I could still access the grease zerk. And yes, I did fill this "new" to me adapter with fresh grease.




I'm not sure how clear this explanation will be, but I also had trouble fully tightening the adapter, and honestly spent a few hours fiddling with it. For reference, I'm talking about the shiny part between the dark colored part on the right (that goes into the transfer case), and the main housing of the adapter on the left.



The adapter has a threaded portion with a free spinning nut to go over the part that goes into the transfer case. Except, as you tightened the "free" spinning nut it stops being free spinning and would unthread from the adapter. The very narrow hex portion between the adapter body and "free" spinning nut is far too small for any wrench to fit on it to keep it from turning while the other is tightened. I wanted a firm seat on the transfer case shaft spindle (to keep the oil seal spring in place) and figured the grease in the adapter would be much less likely to "flow out" if not perfectly tight. So I put a number of thick layers of thread tape on the portion that threads into the adapter and then tightened the "free" spinning nut on the spindle shaft assembly. It's probably unthreaded by ~1 - 1.5 revolutions. Pictures would make this more clear, but my apologies, I didn't take any at this point as my frustration mounted.


I will report how close the speedometer is to a GPS reading as soon as I take a copilot for a ride to operate the electronics.

 

[onegmjack]

Did you put grease in the seal? The grease helps hold the spring in place.

 

[Valence]

Did you put grease in the seal? The grease helps hold the spring in place.

No.
Also, I've never heard of that before and don't understand how a lubricant will help hold something in place. The spring isn't suppose to move or spin at all. Can you please explain how greasing it is suppose to help?

It wouldn't have mattered in the previous install orientation because the spring opening side would have been pointed toward the transfer case and the gear oil would have washed the grease out in short order. With this new speedometer adapter, I have the spring opening side facing the speedometer adapter housing and when you pump in grease via the zerk, grease comes out of the area where the seal is. So I suppose in this orientation it will be greased.

 

[daytonatrbo]

Did your speedometer cable or drive make any funny noises?

My transmission has a high speed hum, and I'm hoping its just the speedo cable and not the output bearing as another member found to be the culprit on his truck.

 

[Valence]

Did your speedometer cable or drive make any funny noises?

My transmission has a high speed hum, and I'm hoping its just the speedo cable and not the output bearing as another member found to be the culprit on his truck.

No, sorry, I haven't noticed any such noises or hums. My speedometer cable is only 5 years old and ~1800 miles (the original one was broken when I bought my truck). I wouldn't think that the cable could make a noise loud enough to be heard over the rest of the truck, except for maybe when it breaks.

 

[daytonatrbo]

No, sorry, I haven't noticed any such noises or hums. My speedometer cable is only 5 years old and ~1800 miles (the original one was broken when I bought my truck). I wouldn't think that the cable could make a noise loud enough to be heard over the rest of the truck, except for maybe when it breaks.

Thanks for the reply. My sister used to have a toyota truck that had a dried out speedometer cable and it made a HORRENDOUS noise in the cab. I figured on a larger truck, the noise would be equally larger. I'll definitely be lubricating mine to see if any difference is made. The fact that the speedometer jumps around so much had me thinking along those lines.

 

[Valence]

Due to the design of the 1:200 adapter, I wasn't able to keep the same orientation of the adapter on my transfer case

As can be seen below, if left this way you would be unable to access the grease zerk. So I rerouted my speedometer cable over top of my transmission and down the passenger frame rail (not pictured) so I could still access the grease zerk. And yes, I did fill this "new" to me adapter with fresh grease.

View attachment 587573


I'm not sure how clear this explanation will be, but I also had trouble fully tightening the adapter, and honestly spent a few hours fiddling with it. For reference, I'm talking about the shiny part between the dark colored part on the right (that goes into the transfer case), and the main housing of the adapter on the left.

View attachment 587574

The adapter has a threaded portion with a free spinning nut to go over the part that goes into the transfer case. Except, as you tightened the "free" spinning nut it stops being free spinning and would unthread from the adapter. The very narrow hex portion between the adapter body and "free" spinning nut is far too small for any wrench to fit on it to keep it from turning while the other is tightened. I wanted a firm seat on the transfer case shaft spindle (to keep the oil seal spring in place) and figured the grease in the adapter would be much less likely to "flow out" if not perfectly tight. So I put a number of thick layers of thread tape on the portion that threads into the adapter and then tightened the "free" spinning nut on the spindle shaft assembly. It's probably unthreaded by ~1 - 1.5 revolutions. Pictures would make this more clear, but my apologies, I didn't take any at this point as my frustration mounted.


I will report how close the speedometer is to a GPS reading as soon as I take a copilot for a ride to operate the electronics.

Drove the truck yesterday and the speedometer was driving backwards (the odometer rolled backwards, needle stayed at zero).

Not sure how the adapter can be reversed because either end is very different and obviously intended for the given setup. By this I mean, the end the speedometer cable went in was obviously for the speedometer cable as it was a slotted female end and the other side was a square male end for the shaft with the flange into the transfer case.

 

[frank8003]

Now this is real interesting, "backwards driven".

 

[gringeltaube]

Well, I must admit that when I saw what you had come up with, my first thought was- that's a tach drive - and how could that work if those rotate in the opposite direction...! But then I kept my mouth shut because sure enough you had tried it out, first...


G.

 

[Valence]

Oops

Well, I was a bit curious when I had the fan and radiator off my deuce this last weekend and noticed how the tachometer looked very similar, though I didn't see a grease zerk (I looked), but moved on with the other task I was working on.

Time to e-mail Big Mike's Motor Pool (where it was purchased from).

Edit:
Double checking my pictures from earlier, you can clearly see "Ratio : 2000" --- That should have clued me of, if I were a wiser man.

 

[Jeepsinker]

Ok, reviving this again because mine is leaking and I've found some pertinent information that isn't here.
The NSN for this part is 6680-00-864-3018.
If you Google it, it comes right up. Parttarget lists multiple listings for it, and I have requested a quote on one unit. Will advise on availability when I hear back. I like factory replacement parts when available.

This is the same part used on the 809 and 939 series trucks, so obviously it is still out there. Just none of the dealers have them.