Thread: Discovery 4 zf 6hp26! auto gearbox leaking

Originally Posted by Vouge SE

None of this explains why I drained 5.5L of atf and could only refill 4L

It is always good to recheck after some use and when in the required temp range - engine running, in gear etc. I bet you will have to add more.

I will pose this question just as a double check - the leak is not water from the A/C system is it?

Garry

Originally Posted by Vouge SE

Possibly the oil cooler is shot, seems to be a common fault.

I’ve got my hands on an inspection camera so I’m going to have a better look this afternoon

None of this explains why I drained 5.5L of atf and could only refill 4L

Other than it was overfilled previously, which though it difficult. Are you sure you’ve filled it enough? Ran it through the gears etc and filled it with the engine running?

Definitely not AC water & yep followed the refill procedure, up to temp and cycled through the gears multiple times.

I’m still of the opinion it’s atf fluid not engine oil.
I got an inspection camera in there and it is somewhat wet around the bell housing flywheel side on the inside. Not sure if it could deep in from above in there as well if it’s not the rear main seal. It is wet all over the top of the bellhousing outside but I have also had the oil filter not fitted properly in the past which spilled a large leak over the back before fixing it

Only other possibility i can think of is a blocked breather on the trans and pressure has built up and pushed fluid out the top ?

I did have a look at the breather pipe end and it’s bone dry.

Just found a video on the 6hp26 transmission test down and it mentioned that the unit did not take any more oil after the initial fill as the transmission pump was broken.

Makes sense why I dropped 5.5L and could only refill 4L

Transmission pump must be on its last legs and leaking

Originally Posted by Vouge SE

Possibly the oil cooler is shot, seems to be a common fault.

I’ve got my hands on an inspection camera so I’m going to have a better look this afternoon

None of this explains why I drained 5.5L of atf and could only refill 4L

As you drain ATF, the torque converter empties as well, when you refill, you need to have the engine running so that the intergral pump inside the transmission fills the TC again. If done 'cold', thr TC does not fill up. These transmissions need to be filled at the correct level whilst the engine is running as otherwise it will be underfilled and the sump will be empty, causing air entrapment in the valve body and very poor shifting. I hope you refilled 'hot' and monitored temperature to get right fill. From memory 35deg C and atf coming out the rh fill hole.

Only half the TC is drained unless you run the engine and pump it out.