BW4406 Noise Level

[Bronco Guy]

I have a question for those that have swapped in a BW4406 transfer case. I installed a junkyard one 3 years ago and I seem to remember it being louder than the original t-case when I first swapped it, but thought it was normal. Over the 3 years, it's been my daily driver and over the last year, I seemed to notice a new noise come up that was pretty mild, but sounded like bearings spinning dry or something like that. Fluid level was fine, but this noise got worse over time so I decided to buy a rebuilt unit from Zumbrota and installed it a couple weeks ago. This new one has a high pitched square cut gear whine that starts around 35 mph and increases with speed. It was concerning enough that I had a transmission shop owner ride with me for a bit to listen to it, and he didn't think it was anything to be concerned about, but it doesn't seem right to me for a chain driven transfer case. Just wondering if I'm being hypersensitive to noise with the new t-case since I just replaced the original one specifically for weird noises.

 

[410Fortune]

Very interesting
I don’t hear any strange whine over a normal t case on any of my 4406 rigs manual shift or electric shift

What fluid are you running?

If you remove front d shaft does the noise go away? Thinking it could be your driveline or front diff?

 

[Bronco Guy]

Very interesting
I don’t hear any strange whine over a normal t case on any of my 4406 rigs manual shift or electric shift

What fluid are you running?

If you remove front d shaft does the noise go away? Thinking it could be your driveline or front diff?

I'm running the recommended Dex-Merc ATF fluid. As an experiment, I ran it in 2WD with the front driveshaft *and* the shifter removed and it still has the same noise. I also had a brand new rear driveshaft built for it and had the front shaft balanced. No change. When the shifter is attached, if I grab the shift knob and squeeze it or push on it, the noise gets noticeably louder. I also listed to it while up on jackstands with a mechanics stethoscope and was pretty sure the noise was coming from the transfer case, but possibly could be coming from the transmission too.

 

[Bronco Guy]

I have a pretty strong hunch that the shop that rebuilt the transfer case failed to install the oil pickup tube so the noise I'm hearing is the oil pump running dry. The oil pump is essentially a square cut gear design which is the type of noise I'm hearing and the sound is loudest from that part of the transfer case. I drained the fluid yesterday after around 800 miles of use and it was pretty dark. I pulled the case out and took it to a local shop for disassembly, inspection and rebuild as needed so I should know soon what the problem was.

 

[tinman_72]

I have a pretty strong hunch that the shop that rebuilt the transfer case failed to install the oil pickup tube so the noise I'm hearing is the oil pump running dry. The oil pump is essentially a square cut gear design which is the type of noise I'm hearing and the sound is loudest from that part of the transfer case. I drained the fluid yesterday after around 800 miles of use and it was pretty dark. I pulled the case out and took it to a local shop for disassembly, inspection and rebuild as needed so I should know soon what the problem was.

I would have sent it back to Zumbrota. They have a 3yr warrantee. At least they do on the AWD units.

 

[Bronco Guy]

I would have sent it back to Zumbrota. They have a 3yr warrantee. At least they do on the AWD units.

I will try and get them to warranty it, but they do expressly state that warranties do not apply to modified vehicles and when you fill out the warranty information, you need to put in the VIN and obviously I can't use my Explorer VIN since it did not come with the 4406. If it turns out it had a problem, I'll try to get something out of them. I didn't want to send it back to them only to have them say that it's fine. I'm still not 100% sure that the problem is in the newly rebuilt transfer case. I also didn't want to have my vehicle down for 2-3 weeks while I ship it to them, have them disassemble/inspect/rebuild and ship it back. My Explorer is my daily driver which is why I bought a rebuilt case in the first place. I needed to be able to swap the old one out for the new as quickly as possible.

 

[410Fortune]

Junk yard? Get a spare very
Little downtime
Lots of 4406e shift out there
Can just shift it with plyers until your 4406m is ready


Rebuild yourself? Nobody does it like yourself!

 

[tinman_72]

...they do expressly state that warranties do not apply to modified vehicles...

Ah, I forgot about that little stipulation. Still worth a try. Worst that can happen is they will say no.

 

[Bronco Guy]

Ah, I forgot about that little stipulation. Still worth a try. Worst that can happen is they will say no.

That's my plan.