ZF5HP24 details
 

Thought I'd put this out to the E53 "AI" minds, as I consider a cooling upgrade to my E53. I've pinged a few individuals and am looking for more advice and lessons learned hopefully.

I definitely don't want to reignite any cooling wars or skirmishes but would like to ensure I understand any finer points and possible showstoppers to what I am planning. Bottom line: I'm a fan of lower t-stats, but only if the entire system is able to accommodate the change. The heat made by the motor has to go somewhere so if the motor is made to run cooler, the system will push the heat to another component, namely the radiator, a known weak point with its plastic tanks, etc.

Therefore I'm looking at the CSF Race S62 E39 M5 radiator, which is an all-aluminum, dual pass piece which hopefully will need no, or little in the way of fitment mods, and offer greatly enhanced cooling capacity in the deep south summers where my car lives. However, it doesn't have the small fitting for the tranny cooler on the bottom left corner (M5 was a manual only). My planned solution is an OE tranny cooler delete. I will mod the cooler side lines to AN fittings and add a suitable air to oil cooler behind or in front of the radiator. I think the CSF Universal coolers can't be beat for durability and cooling capacity: https://csfrace.com/csf_products/universal-oil-coolers/ Air coolers are larger, but there should be room, especially with the SAP delete I've done.

I already run their "Boss" Universal cooler for engine oil and may just use that, or ever the smaller 8119 model if I can determine it will do the job. Frankly, I can't see how the tranny develops more heat than the motor, and my oil cooler gets piping hot around the inlet/outlet port side but is always quite cool on the other half, which tells me it is over sized for the task of blazing hot M62 oil. It holds the oil temp rock solid at 95 deg C in all conditions. ZF tells me that the operating range for the 5HP24 is 170-190 with the Lifeguard fluid and mine is always at the top of that, or a tic over. I assume this is due to fact that I'm running more torque from the 4.6 motor through the 4.4 OE transmission and maybe also a function of a 22 year old cooler too. I'd put in an in-line t-stat to hold the temp at the 170 end of that range. They didn't tell me the operating PSI though, saying they don't support mods to their products since they are an OE mfr.

So, in an effort to size my cooler and lines/fittings appropriately I've been hunting for details on the 5HP24 operating pressure but am struggling to find anything definitive. Bayonet fittings and band clamps would be easy to splice into the OE cooler lines, but something more robust may be needed if the pressure is too high perhaps? I found a research paper where the guy used a 4HP24 to study something or the other and measured pressures in the 100PSI range (plus/minus depending on which gear set he was measuring at). Higher than normal motor oil pressure, but perhaps reasonable I guess. I also found a repair manual from a transmission repair chain that said the pump output was between 43 and 45 GPM, which seems astoundingly high. I'm wondering if that was a typo.

Anyone have carnal knowledge of these ZF5HP24 operating parameters?

CSF Boss Universal cooler I use for oil, in conjunction with the Gulf car oil filter housing that has cooler ports and a built in t-stat. Not intestinally going for theX5 Japanese drift car look, but the cooler is really, really solid and has already survived a rear-end "bump" courtesy of my daughter with only a little paint scuffing. So I think I am going to leave it in this location.
https://i.postimg.cc/zfjxj0Cn/X-Oil-Cooler.jpg

Not to derail but to add another possibility...
up to 09/98 e39 540i came with an air cooler for the transmission
17221740798 with frame 17111740796
Attach that to the E39 540i / m5 CSF radiator 7064
Buy the inlet and outlet hoses for the pre 09/98 auto e39 & splice them into the existing transmission cooler lines on the x5

No welding, no mess, no modification to the radiator etc. Even if that OEM transmission cooler is meh in regards to performance it's better than the engine temp cooler we currently have...

I have a fan delete in mine so I know I have the space for the bracket & cooler off the back of the radiator.

Thanks for the lead, I will do some more research. Ironically my neighbors truck blew the integrated tranny cooler into the radiator this past weekend. One new radiator, pump, hoses and two flushes later and he made it 5 miles before the tranny fail safe came on. I suspect the coolant went the other way too, into the tranny, but it could have overheated too due to a clogged cooler line that didn’t get flushed out well enough I suppose. Apparently his model ford truck is well known for doing this.

ZF got back to me with an answer to my 5HP24 pressure question, which I was struggling to find on the web. Maybe they had a change of mind: “5HP24 cooler pressure is about 2 bar. The pump pressure can be up to 20 bar or so at fuel, throttle.”

So about 29 psi at the cooler and up to 290 psi at the pump. 29 psi is low, so I don’t think anything cosmic is needed if I go the route of modifying my cooler lines to AN on the cooler end to go with an aftermarket cooler. Likely just chop the lines in the rubber lengths, push in some barbed AN couplers, hose clamp and run the AN lines to the cooler.