Transfer case leak issue - relief reservoir?

[Triskal]

2008 Explorer Limited 4.0 5spd 4x4 200k+ miles

Last July (2021) I had the transmission rebuilt after some slipping issues. They provide a 3yr/36k warranty. Unfortunately I have had to take it back to the shop for warranty work a few times. The most recent was July of this year for a new valve body, torque converter, and pump seal.

Since then it has developed a leak that turned out to be the transfer case. That transmission shop looked at it and said that was not part of their work and so not covered under warranty. I took it to my regular mechanic and they believe it is because of a missing relief tube/reservoir/value/thingy on top of the transfer case. They said the trans shop would have had to drop the transfer case in order to do the work and it appear they did not reinstall the relieve reservoir. They said it is supposed to allow fluid to expand out when it is hot and the return to the case when it cools. Since the reservoir is missing the fluid that expands out just leaks down the side.

I am assuming that has resulted in a drop in fluid levels. The Explorer has also developed a clunk when moving from forward to reverse gears and hitting the gas. It does not happen immediately when shifting but only when you hit the gas - almost no matter how delicately you press the gas pedal. At first it was occasional and not very loud. Now it is every time and gotten louder. The regular mechanic says it sounds like it is coming from the transfer case. My thought is this is happening because of a drop in the fluid level. I have parked it until I can get this resolved.

So my question for this group is this - is what the regular mechanic is saying sound correct? Do I have a case to make for warranty work form the trans shop for having not reinstalled that part?

 

[Rcflyer330]

so what the transfer case has (its the same with any gear case) is a vent tube that goes up higher in the vehicle to prevent water from getting in. there is no expansion tank. the transfer case is the tank and you dont fill them 100% full with oil this allows expansion of the of the fluid and the vent hose is there so pressure does not build up blowing out the seals causing all the fluid to leak out. i would say if the hose was not connected you could get a little oil spray comming out the vent hole would it be noticeable that i dont know.

the clunk that could be literly be any part in the drive train or drive line but the most likely parts are u joints, motor mounts, or transmission mount.

 

[Triskal]

so what the transfer case has (its the same with any gear case) is a vent tube that goes up higher in the vehicle to prevent water from getting in. there is no expansion tank. the transfer case is the tank and you dont fill them 100% full with oil this allows expansion of the of the fluid and the vent hose is there so pressure does not build up blowing out the seals causing all the fluid to leak out. i would say if the hose was not connected you could get a little oil spray comming out the vent hole would it be noticeable that i dont know.

the clunk that could be literly be any part in the drive train or drive line but the most likely parts are u joints, motor mounts, or transmission mount.

Great info. Thanks a bunch. I will get another opinion before going back to the trans shop. I have lost faith in them and would like some more feedback before going to them with another warranty claim.