Finding the leak, NP435 or D20??

[Bundy]

i am trying to trace a decent leak that starts with my NP435 or the D20. after scrubbing/dregreasing i drove it for a bit and the there was oil on dripping from the bottom of the D20, but not as much from the tranny.

there is no obvious leak from the output shaft, i can't see where the tranny and the TC mate because of the crossmember but this seems like the culprit.

on the D20, there is a lower drain plug and it looked like two fill plugs- one was way too low to be the right filler and the second it about 1/3 of the way up. when i opened that fluid came out and i closed it quickly. i think i read it holds 1.5 or two 2 quarts?

the NP435 took about a half a quart, not alot but more than the TC. i think i read it takes 2 or 3 quarts?

Anyway, my main question is could it be the gasket that seats the TC and tranny? also, my tub is rhino lined over the tunnel but i can see screws under the lining and can make out what i think is a removable tunnel panel. before i rip up my lining, i want to make sure it will tell me something.

thanks!

 

[73stallion]

if the t-case is over full, the seal between the trans and t-case may be bad. it'll let oil flow from the trans to the dana 20. i've had to replace this seal on a C4 before because we had 1" of red fluid floating on top of gear oil.

if this is the case, it may be blowing out of the vent o top of the t-case because it's over full. let me know if you want me to come over and help trouble shoot. i'm free tomorrow morning, most of tomorrow afternoon, and all of monday morning.

 

[Broncobowsher]

if the t-case is over full, the seal between the trans and t-case may be bad. it'll let oil flow from the trans to the dana 20. i've had to replace this seal on a C4 before because we had 1" of red fluid floating on top of gear oil.

if this is the case, it may be blowing out of the vent o top of the t-case because it's over full. let me know if you want me to come over and help trouble shoot. i'm free tomorrow morning, most of tomorrow afternoon, and all of monday morning.

What he said. Saves me the typing.

 

[Bundy]

Thanks Ben- Where should the transfer case be filled to? I thought i read you could fill it through the top, so maybe the PO overfilled it.

 

[Viperwolf1]

The D20 fill plug is the one at the rear about 1/3 the way up. Fill it until it starts coming back out.

 

[Bundy]

this leak is getting worse i think- it looks like it is coming from the area of vertical mount between the TC and the crossmember... the mount is saturated to all hell, the rubber is almost turned to an ooze.

is there a seal typical of leaking in that area? i am just trying to get a guage on what i need to do in pulling the tranny or just the TC, or if i have to pull botch at the same time.

I also have been checking the oil levels on both, but nothing noticeable yet. gonna drive her some more and see what's low i suppose.

 

[thegreatjustino]

the mount is saturated to all hell, the rubber is almost turned to an ooze.

is there a seal typical of leaking in that area?

There is a gasket between the adapter and NP435 as well as a gasket between the adapter and the Dana 20. If one of the gaskets sprung a leak, that would explain your mess.

FYI, for all the times I have put the transmission/adapter/transfer case assembly back together, I have never used an actual gasket. Just a bead of silicone around the face of the adapter.

 

[Bundy]

There is a gasket between the adapter and NP435 as well as a gasket between the adapter and the Dana 20. If one of the gaskets sprung a leak, that would explain your mess.

FYI, for all the times I have put the transmission/adapter/transfer case assembly back together, I have never used an actual gasket. Just a bead of silicone around the face of the adapter.

justino, this may be the case afterall. The tranny and the TC both shift well, so it's not like they are beat up but the rig did sit for quite a few years (bad rings too )

If i wanted to redo this gasket on the adapter, do i just need to drop the TC? If you don't mind spelling out the repair process for me, i would love to hear it.;D

 

[thegreatjustino]

In order to remove the transfer case from the adapter while leaving the transmission and adapter in the Bronco, you will need to remove the transfer case mounts as well as the cross member. There is a bolt that you can't get to with the cross member still installed. Remove the transfer case from the adapter (careful not to lose your output shaft bearings) clean the mating surface on the transfer case, as well as the adapter. Put a 1/4" bead of silicone around the face of the adapter, re-install the transfer case on the adapter. Torque bolts to spec and reinstall the crossmember. It would be a little easier if you drained the gear oil from the transfer case first, but I have done this with the oil in, so it can be done.

If I were you and I was not sure which gasket was leaking, I would pull the adapter off the transmission and re-do that seal with silicone as well since you've already got half of it apart.

 

[Bundy]

will the tranny be okay only supported by the bell housing since i am removing the crossmember? and when you say to be careful not to lose the output shaft bearings, do you mean losing them internally in the TC or adapter, or just generally speaking, don't lose them? (lol)

lastly, do i need a tranny jack or something or can i man handle that bitch?

 

[Bundy]

just an update on this for anyone in the future, i couldn't reach the driver's side crossmember bolt because of my auxilary gas tank- had to cut a socket size hole in the floor but worked out.

now that both the crossmember bolts are out, i think i am removing the two mounting bolts and then i should be able to remove the crossmember and get to all the TC/Adapter bolts.