Hello Everyone

 

So my truck has developed a new issue this past weekend.  Heading home from the mountains I was cruising at about 75 in 5th gear.  Pulled out to a pass a truck and began to accelerate.  Let off for a second and the transmission began to make a clunking/knocking ticking sound.  Kind of sounds like the teeth are slipping past each other or not meshing correctly.  Only happens in 5th all other gears seem fine.  I'm thinking I either lost some teeth on a gear or the shift fork/pins brake and its not engaging the gear all the way.  Anybody experience anything similar?  Finally do I have to pull the transmission to change out the overdrive gears if that is the problem?  The transmission was rebuilt by a reputable shop about 70000 miles ago so I don't think its in too bad of shape other than said issue.  Truck is a 98- 24v,  4x4.  

 

Thanks

Bill 

Sounds like you're having the famous 5th gear nut problem 

Just now, Dieselfuture said:

Sounds like you're having the famous 5th gear nut problem 

Its possible I have been down that road before.....   It would be an updated shaft failing this time if it is.

391k miles. Never had a 5th gear nut problem and never broke the input shaft. 

 

OEM shaft I broke at the 3rd/4th shift ring. Now running the upgraded mainshaft. Make sure if you going to tight that again make sure to get the sockets and the torque spec. Don't quote me be I think the upgraded shaft is like 600 foot pounds on the nut. This is why I laugh at all the YouTube videos of guys hammer and chisel the nut on and then tack weld the 5th gear nut. This will not work and will fail again.  

 

Still currently using the Mobil 50 SAE Trans Fluid no issues to date. Working awesome and heading to 150k miles. 

 

Have you seen a nut failure on an upgraded shaft? I’m thinking it’s something else this time. But yes I agree if I take it off I definitely need to assemble it correctly. 

Just now, Rotax3006 said:

Have you seen a nut failure on an upgraded shaft?

 

Nope. Still working perfect. 

How much do you trust your shop that did rebuilt. They could of said new shaft and didn't. Other than that grinding clunking in gear when I had my Mustang with t5 meant that the main cluster great had teef missing. Not sure on nv4500

55 minutes ago, Dieselfuture said:

How much do you trust your shop that did rebuilt. They could of said new shaft and didn't. Other than that grinding clunking in gear when I had my Mustang with t5 meant that the main cluster great had teef missing. Not sure on nv4500

It was inland truck parts here in Montana that did it. They seem pretty reputable. Plus the company I was working for did a lot of business with them.  This failure seems different than the nut coming off. I guess I will tear into it and find out. 

Well guys I finally got it torn down.  Not a nut failure this time.  The mainshaft gear stripped 3 teeth off.  It looks like one may be fatigued cracked/shock load not sure, the guys at inland truck said they don't see many like that.  I do have an updated mainshaft with the 3 piece washer set.  The retainer rings seem loose to me. When installed the gear can still move about .025 or so.  I'm thinking the washers are worn thin and allowed the gear to move in and out and hammer the teeth to the point of failure. I have ordered a new retainer set as well as a gear and associated seals.  We will see how it all fits together with new parts.  May replace the mainshaft as well if the gear seems loose. 

 

Yup. Just got done with the exact same problem. My last rebuild the lower gear was replaced but this gear wasn't. Fatigue took its toll and sheared off the whole patch of teeth. Now both gears are replaced and new brass syncros. No carbon fiber. Still running the 50 SAE Mobile Trans Fluid.

I saw those photos on your post. Pretty substantial damage. Mine didn’t damage much except the mainshaft 5th gear, looks about like yours everything else seems fine. Headed over to torque king on Monday to see what they think. Seems to be a little play in the slot where the 3 piece split washer goes. Not sure if that needs to be tight or not.  Bought a new split washer thinking it was worn. Measures essential the same as the old one. Hard to believe the shaft wore that much without the washer wearing.