Tansmission Temperature thoughts ---

[civdiv99]

Some of you may recall maybe 1 1/2 years ago I did a garage rebuild of my 5HP24. I used a Mobile "multivehicle" synthetic trans fluid. It's been fine.

Now, I also run a B&M trans cooler up front - it fits nicely between the electric fan and the radiator. More thoughts on why I do this follow.......

I posted some info maybe a month ago on reading the trans temp with a multimeter. Of course a IR gun will give ya close enough - I have additional plans for the process I outlined so tossed it on the board while I was at it. But I'd be curious to know if a few of you could hit your pan with an IR therm and let us know what your trans pan temp is after driving around on what counts as a 'warm' day.

It just drives me nuts that BMW will run the trans as hot as they do. I'd bet way over 200 degrees fluid temp. They do this to accomodate the "lifetime" fill idea as the oil needs to exceed boiling point of water to boil off moisture that may condense inside since it's not getting changed. (The trans vent tube is tucked way up in the tunnel).

Since I am not running the lifetime secret squirrel sauce, I am going to have to change it regularly anyway (not that I'd consider the other stuff lifetime in terms other than the "transmission's" lifetime).

The 5HP24 first use was in what - 1995 (ish)? So was under development to whatever extent before then. Way before the secret squirrel sauce and lifetime fill mantra. Now here's where I am going with all this rambling. The ZF kit for my 2002 covered the whole range of years and applications. In other words, the o-rings and seals and various other part numbers didn't change over time and aren't unique to BMW applications. They are the same parts as when 30K changes were commonplace. While I suspect this high $$ fluid is more tolerant of operating temps that seem contrary to good trans oil life, I'm not convinced it's necessarily the best plan. Best compromise to sell cars with a minimum of req'd dealer svc maybe -

Anyway - I would really like anyone using stock trans setup to give us some readings off the pan after driving around or highway trip - I want to know what you see.

And second point, granted I'm a tinkerer, but for those of you (like me) who have strayed from the lifetime fill koolaide, you might want to consider not just the fluid properties in terms of compatibility, but realize that even quality trans fluids generally have a problem with high temps - and trans fluid life drops precipitously when you get well into the 200s. I'm running in the 150s right now, but it is not hot (or warm) out.

Hell, I have a class A motorhome running an Allison with their synthetic transsynd fluid ($$!!!!) The Allison folks included a chart reflecting shortened trans life and effects of temp. That thing only runs trans temp of maybe 170 across Nevada in August (I have a digital readout).