M998 Hmmwv Speedometer gear pin shearing!

[DocBreckon]

Im fricking frustrated. I recently did a reseal and put in a new 15366 1/2 case on my NP218 T case since the original case from Auction was cracked. Im guessing they probably lifted with a fork and cracked it. . It was a Piece of cake to rebuild the T case. I did it all in my garage, took 5 hours . All of the Internal parts including the 155 needle bearings were all ok. I removed every part and inspected them. I.E. original internals that included the bearings, the bearing sleeves, drive chain etc. Since the reset in 04 they were all ok. Now I keep shearing the radio pin and the Speedo quits working completely all together. (Radio pin is the square junction pin between the orange Speedo input shaft and the 90* reduction gear adapter going into the top of the T case) I’m no newbie to wrenching on vehicles. Done it for 30+ years. I Co-Stared on Discovery channels Vegas Rat Rods first season so I’ve been around and can work on anything and do it right the first time . The shearing of the speedometer pin has happened twice now, both times after only a short 60mph 1/4 mile trip on the freeway. I cannot avoid it going to one specific location. Today was the 2nd time.. Any ideas why? I have the input gear clocked correctly to the correct slot in the top of the T case input! This is killing me. When it breaks, the 1/2 of the square radio pin gets stuck in the body of the input sleeve on the orange gear and it cannot be removed!! It’s getting annoying and costs me $40 each time in a new orange speedometer gear and radio pin. Help if you can. It’s not simply a bad input pin, bad Speedo gear or Speedo cable or Speedo. All are new!!! Is it that the Hmmwv’s don’t like freeway driving at 59 mph even for short periods???? Has the Original Factory POS 6.2L , TH400 and NO218M currently but which will be swapped to a P pumped Cummins 5.9L 6bt, an Allison AT545 and a NP205 Divorced case soon.

 

[doghead]

If you replaced the cable yourself, did you route it correctly?

 

[DocBreckon]

Yes. 100% routes the same way. I made sure there was no kinks and even turned the cable freely by hand before installing it into the Speedo head and the 90 degree adapter. That’s what is frustrating. It’s exactly as it was. The first one was fine until the freeway, same on the second one. I just ordered another Speedo gear. (Btw, they are the same as Jeeps , 35 tooth long, but only $16 shipped as opposed to $40 for Hmmwvs)

 

[DatGuyC]

If that 69mph isn't a typo then that might be your problem. You might be bottoming out the speedo and shearing the pin?

 

[patracy]

If that 69mph isn't a typo then that might be your problem. You might be bottoming out the speedo and shearing the pin?

I've taken mine to that speed before, but not on purpose. Interstate speeds and the constant drone tends to make me slowly speed up until I realize I'm "breaking the sound barrier" in it and let off. My speedo still works. (Knocks on wood though, because the next time I accidentally get up to this speed again it'll surely fail!)

 

[papakb]

When I first got my HMMWV I had the same problem and what I found was the 90 degree gearbox wasn't tightening down squarely onto the TC. That little angular offset would cause the pin to shear after a couple days of driving.

 

[Action]

Yeah, it would likely be something between the square pin and the speedo. Something is keeping it from turning freely. speedo gears glogged up, kink in cable, grime in cable (maybe not noticeable by hand turning), crooked elbow, etc.

 

[DocBreckon]

I’ll pull it apart again. I’m expecting the pin to be lodged in the long gear body. I ordered a new one and will swap it once it’s here. I luckily have extra square pins. I’ll lube the 90* box too. I’ll avoid the freeway but ****, you’d think it’d survive a qtr mike at 60 mph. Somethings screwed up. I’m using a gps Speedo app in the meantime.

 

[DocBreckon]

Lol.. 69 Mph.A total typo. It should have been 50. I guess my fat fingers hit the other numbers..I wish I could go 69. That'd be fun.. smh I cant get over 50 MPH without the run flats shaking like mad....

 

[DocBreckon]

I ended up buying another transfer case speedo unit and new gear..

 

[DavidWm998]

I had similar issue but have a new problem now. Now my speed indicated on the speedometer is way off from GPS. Any ideas?

 

[Action]

Change the gear in the transfer case. or the tire size. or the diff ratio.

 

[Usmcsteve]

I’m having similar problems speedometer was not working when I received my 1993 m998. When I removed the speedo gear from the transfer case I found the pin to be broken. Bought a new gear and pin researched how to index the adapter in the case and got it all tightened down. Went to drive and he vehicle still no speedo. Removed the gear again and attached a drill as I have read on earlier posts. While spinning the drill the speedo would move. I have no idea where to go from here. Any help is appreciated

Steve

 

[osteo16]

I’m having similar problems speedometer was not working when I received my 1993 m998. When I removed the speedo gear from the transfer case I found the pin to be broken. Bought a new gear and pin researched how to index the adapter in the case and got it all tightened down. Went to drive and he vehicle still no speedo. Removed the gear again and attached a drill as I have read on earlier posts. While spinning the drill the speedo would move. I have no idea where to go from here. Any help is appreciated

Steve

Wondering same.. any luck ??

 

[Usmcsteve]

Wondering same.. any luck ??

Yes you have to make sure all is aligned with the top of the transfer case according to the number of teeth you have. What I did was took A picture with my phone of the top of the transfer case to see exactly where the alignment mark is and then placed the gear in the transfer case with the number of teeth aligned with the alignment mark.
hope this helps

 

[osteo16]

Yes you have to make sure all is aligned with the top of the transfer case according to the number of teeth you have. What I did was took A picture with my phone of the top of the transfer case to see exactly where the alignment mark is and then placed the gear in the transfer case with the number of teeth aligned with the alignment mark.
hope this helps

Yup, I did rebuild the NP218 last winter and everything aligned and went together well. And I clocked the alignment correctly for my gear.. I think the end of my speedo cable might be the culprit. But to further my conversation here, as I rebuilt the 218 I did see a bunch of speedo gear fragments in the case, obviously it had been trashed over time. It had been like this for a bit because the bottom tip of the speedo gear had worn an indention into the bottom of the Tcase.. Now, I've been looking everywhere but cant seem to come to a conclusion here.

WHEN THE SPEEDO gear is placed into case, does it SIT on any kind of post or anything in the case???
Or does it simply drop in and rest on the transfer case worm type gear for the speedo gear ??? well if anyone has any input, would be obliged. Ill start with the cable, Its only a few bucks and go from there.

And I should apologize for the hijack, but the thread is a few years old. So i'll save my apologies for later, might need em.

Ocho Out

 

[Usmcsteve]

Yup, I did rebuild the NP218 last winter and everything aligned and went together well. And I clocked the alignment correctly for my gear.. I think the end of my speedo cable might be the culprit. But to further my conversation here, as I rebuilt the 218 I did see a bunch of speedo gear fragments in the case, obviously it had been trashed over time. It had been like this for a bit because the bottom tip of the speedo gear had worn an indention into the bottom of the Tcase.. Now, I've been looking everywhere but cant seem to come to a conclusion here.

WHEN THE SPEEDO gear is placed into case, does it SIT on any kind of post or anything in the case???
Or does it simply drop in and rest on the transfer case worm type gear for the speedo gear ??? well if anyone has any input, would be obliged. Ill start with the cable, Its only a few bucks and go from there.

And I should apologize for the hijack, but the thread is a few years old. So i'll save my apologies for later, might need em.

Ocho Out

It just drops down and aligns with the gears in the transfer case.

 

[frank8003]

Don't need speedometer anywho, just use GPS on your phone.
What is essential is the RPM so not to lug the puppy

 

[Mogman]

If that 69mph isn't a typo then that might be your problem. You might be bottoming out the speedo and shearing the pin?

Can't really "bottom out" a speedometer, they are magnetically driven so the needle may stop moving but nothing is going to bind up.