What does it sound like when an NV4500 goes bad?

[Chad Mac]

I've got a popping noise that has stumped me for about 6 months now. It only occurs in 5th gear and this gear is also the loudest. Gears 1-4 are quiet and smooth with no popping. This popping sound used to be about every second at 65 mph, now there is an intermittent pop every half second between the pop that occurs every second and 5th gear seems a lot more noisy. It doesn't seem like it robs the motor of any power and there is no slipping of the clutch. What does it sound like with an NV4500 (or it's syncros) go bad? Has anyone else ever had a popping problem in only one gear? Please help!

[rjschoolcraft]

Sounds like a tooth off one of the gears at the back of the transmission. Since you only hear the sound when in 5th, we can rule out the main input mesh. That leaves either the countershaft gear or the output gear for 5th speed range at the back of the engine. Since the frequency of the popping sound has increased, I suspect another tooth is now gone. If you go much longer, you'll lose 5th altogether.

[Chad Mac]

Thanks Ronniejoe! Have you every heard of this before? What would you recommend at this point? What would cause this? I did change out the transmission oil about 60,000 miles ago with Mobil GL-5 and had the clutch replace about 20,000 miles ago. Thanks again!

[rjschoolcraft]

This is typically the result of bending fatigue of the gear tooth. I had this happen once on the main input gear. There was a clicking or popping sound that was present in every gear but 4th (on a five speed Borg-Warner T5). In 4th (direct), the power just flows straight through and bypasses the counter shaft.

There are lots of things that can have this result... manufacturing defect, over torque, scoring that caused a stress concentration, etc. You'll need to pull the transmission and replace the broken gear. Since it's fifth, it's likely not going to be part of the counter shaft clutster gear, so it won't cost an arm and a leg.

[Diesel Dan]

Originally posted by Chad Mac:
Have you every heard of this before? What would you recommend at this point? Yes, have heard of this.
It is fairly common on Dodge/Cummins trucks. Go over to the TDR and look it up. There are vendors that offer upgraded fully splined main shafts for this fix. CTDs that are turned up take out 5th fairly easy, so I've read. Some guys even upgraded to the new main shafts and still stripped them out, then came the NV5600. But I don't thing you'll need to worry about that.

[Chad Mac]

Thanks for the replies Ronniejoe and Diesel Dan! Is this a difficult repair? Is this something that an average shadetree mechanic could do or is this a shop repair? I'd love to hear some details on the repair if you have any. I've done some other extensive and difficult repairs to my truck but have never been inside of a tranny before . . . auto or manual. Thanks again guys!

[rjschoolcraft]

Manual transmissions are easy compared to automatics. I've been through lot's of both. If you can get a hold of a service manual, that will help a lot.

[Chad Mac]

Well, I've been studying and doing some research. :confused: I did find several instances where DODGE NV4500's had a 5th gear problem but couldn't find a single piece of information that pointed to Chevy NV4500's having the same problem. Sounds like what Ronniejoe was talking about but won't know for sure til this weekend when I can take a look at it. The great news (if there can be any about this) is that I won't have to pull then entire transmission out to see what the problem is since 5th gear is actually not in the gearcase but in the tail section only. :D Just the transfer case has to come out. I'm crossing my fingers that it's nothing major. A rebuild will cost me about $1100 if it is. :mad: I'll repost to let everyone know what I found next week. :cool:

[Turbo Al]

Chad, I had a poping noise in 5th (only) and it turned out to be defective limited slip clutches in the rear diff. at the time they had about 160,000 miles on them. Also don't rule out the input shaft bearing (in Flywheel) these make a lot of strange noises esp. when in 4th or 5th.
Good luck
Al

[Chad Mac]

Turbo Al,

Where did it sound like your popping noise was coming from when inside the cab? Also, what did your popping noise sound like? Did it progessively get lounder or pop more frequently? Did you feel any power loss? What other symptoms did you have? Read other post I put in your name so I can ask these questions and more directly to you. Thanks Turbo Al!

[Turbo Al]

Hi Chad,
Sorry I work really wierd and long shifts -- I have two on call jobs so I am sometimes hard to get hold of.
The noise was a fairly loud metalic ratcheting type noise most definately heard inside the cab and sounded like it was coming from the trans. continuous bang bang bang when under acceleration on hills.
The input shaft bearing (in flywheel) will produce a loud vibration or whine esp in 5th gear.
I had my sycro's replaced at about 160,000 miles as well (I ended up tearing the whole drive line out to track down some of those noises) they were still in fair shape but I had them replaced anyway.
My noises came from 4 sources,
1. Input shaft bearing turned to powder
2. Torsion bar rubbing on trans crossmember
3. Rear wheel bearing torn up
4. Limited slip clutch plates shot

Al

[Chad Mac]

That's great stuff Al but it would be great to hear more. I didn't get your email. Please send again so I can get in touch with you. My email is chad_mackenroth@hotmail.com.

Thanks again Al!