Thanks for all those PN. That was more helpful than correspondence I’ve had with ZF and two distributors.

Yes, I’ve read the same thing about the fill hole. It makes no sense to me. While the pan could conceivably change the volume of the transmission fluid in the system, the fluid level should be unchanged if using the original fill plug on the side of the transmission.

I sent a technical inquiry to ZF and they said “they had heard the same thing, and simply suggest using the plastic pan.” Though they acknowledge the steel pan conversion uses ZF parts and is common in the community.

CTSC, which is the only manufacturer with warnings regarding the fluid level, was not helpful in resolving this either. They claim using the side plug will overfill the transmission and cause frothing in the fluid and rapid distraction. Oddly enough, they also note the steel pan holds 1L less fluid that the original plastic one.

As best I can surmise from hours of research on this forum, Disco3.co.Uk, and even some BMW forums is this:

ZF created the steel pan for applications in late models BMWs using the ZF 6HP26 transmission. In BMW applications the transmission fill plug was blocked by the exhaust (or something else I cannot recall), so ZF created this pan with a bottom fill plug. In order to fit the new pan, it needed to be made more shallow along with a separate filter. The fact that it’s steel is make it more rigid since the filter is no longer integrated. LR parts distributors found this pan and realized it solved their problem in Rovers due to the integrated filter. At some point CTSC started selling kits and included this fill plug warning. People on the forums shared the warning, but no one really understands it.

Among the many people I’ve talked to, some use the transmission fill port and others use the new pan fill port. No one has reported a problem in either case. The steel pan should hold less fluid, but I found one reference on this site that it is actually the same. If it does hold less fluid, the transmission could run slightly hotter, but again, I’ve not heard of any overheating issues that were linked to the new pan.

All this to say, the steel pan is probably fine, as is using either fill port. I’d like to see someone with the conversion fill using one port and then check the fluid using both and see if the levels match. Now that I have parts numbers, maybe I can do this!

 

I did measure the distance from the bottom of the original fill hole to the pan mounting flange at 13 mm. I then tried to measure the new pan’s overflow level to the pan flange, and it is lower than the original fill hole, maybe 6-8 mm lower. I didn’t fret over the difference too much, as I still cannot make sense of filling to a lower level due to the smaller pan volume. If the pan was larger, you would still want the same level, regardless the volume.

 

I completely agree. Thanks for sharing those measurements, that’s a significant detail that has been missing in all of this.

 

I think this is the takeaway here.

I am due for a fluid change within 4000 miles, and can try filling up top and re-checking level with the pan hole.
That could be months from now, so someone else is welcome to beat me to it and post here.

(pan hole . . . heh heh)

 

I have to swap pans soon and do another fluid change. Would be interesting to fill via the pan then measure how much more is needed, if any, to get it coming out of the fill plug. So fill at pan til it back flows, button it up, the fill at factory fill plug.

 

Ford gasket I mentioned above is dry as a bone, and the transmission is shifting perfectly.

 

Does the steel pan available there have a fill plug on the side ?, mine doesn't so you have to use the trans fill/level plug. I used a duraprene gasket which came with the pan kit and also bone dry,you cant get the correct level unless you use the trans level plug.

 

It has a fill plug on the bottom. That basically joins with that white plastic T fitting. The fitting it opens at the fill level. So basically you have a shove a hose up in there so it pours ot of the fitting until it starts to them overflow it and come back out. At least that is the theory and I am not certain myself if that live and the fill plug on the trans itself are the same level. Should be?

 

Refresher of pics to show that white fill fitting. And for the gasket, I also get the metal one.

 

I went to order my ZF metal pan kit, but to my surprise they are sold out everywhere. That forced me to hunt down individual parts and I’ve come up with some info worth sharing:

1) The pan bolts in the 6HP26 (and generally any ZF transmission I looked at) are ONE time use. While they are not angle torqued, they are torqued to yield. I believe the bolts are aluminum. In my search of the bolt PN I found many more threads from users reporting broken bolts —in every case, the bolts were being reused.

2) The bolts for the metal pan are shorter and have a smaller head. ZF 0736010347. These are M6x22.5

3) Bolts made for the Ford 6R80 will fit, if you can find them. They are M6x22.5. I finally found a good set for $30 shipped (ATP ZX-220)

4) Bolts for the original plastic pan are cheap and plentiful, be careful not to get these unless you are installing a plastic pan with integral filter. These are ZF 0736 101 486. They are M6x28 (about 1/4” longer than for the metal pan). The head on these is also larger and I presume would conflict with the flange of the metal pan.

Many thanks to P-Bod for helping me sort through some details on this.