75 Series gearbox/transfer case question

[Chisel]

G'day everyone.
I have July 1995 built HZJ75 cab/chassis that's done 175,000k's which I have had since new. So far it's been faultless (hence this is my first post.) On a recent trip I found a lot of transmission oil sprayed from the transfer case right along the under carriage of the vehicle. Although there was a lot of oil - none dripped on the ground from the vicinity of the case whilst the vehicle was stationary therefore it's hard to detect where the oil originated from. A good wipe down and another run didn't help with finding the source. I pulled the transfer case fill plug and it was full but the gear box required about 1.5 litres of oil. There is no evidence of a gear box leak.
My question is: is it possible for oil to transfer internally from the gear box to the transfer case, thus 'over filling' the transfer case and therefore forcing the oil out somewhere? I'm thinking this would only occur if the seal between the box and case (if there is one) has failed??
Any advice would be appreciated..
Thank you

 

[Malahki]

Yes it is a common well known problem with Toyota split cases. It happens when the seal between the two cases fails. The oil is known to travel either direction and can overfill the tranny or T-case to the point it starts coming out the breather. Its a lot nicer if it is overfilling the transmission because you can use a couple fittings and put a equalizer hose between the two cases fill plugs and the oil will run back down into the T-case eliminating any overfill.

I have the same problem you mentioned in my BJ74 with the H55F split case and the tranny oil transferring into the T-case. I use a clear hose between the two case fill plugs so I can monitor how high the oil level is getting in the T-case. Every few hundred kilometres I have to pull the hose off and add oil to the tranny and let the T-case drain back down. Its just a temporary solution until I can get it rebuilt.

Here is a couple threads on the subject:
https://forum.ih8mud.com/70-series-tech/616178-h55f-tranny-t-case-troubles.html

https://forum.ih8mud.com/70-series-tech/278043-anyone-experience-changing-tranny-seal.html

 

[Chisel]

Thanks BJ 71. I have checked the breather on the top of the T-case and it's all clear and not the source of the leak. The rear seal could be getting a little worn and when a bit of pressure builds as the oil gets hot it may be pushing past that seal..?

In light of the above I guess I have to ask is the seal betwen the tranny and T-case difficult to change? I am a 'bush mechanic' so I was wondering if it could be done in the back yard (so to speak?)

Thanks again