icantfindaname2

Hello everyone,

Background
Chasing a torque converter shudder, doing everything before replacing the torque converter / transmission
141k miles, fluid replaced 2x with Liquimoly 1600ATF, new pan with filter, new solenoids with all of the seals
xHP Stage1 trans tune (surges with OEM tune, just at higher RPM as it locks converter)

I was looking at MHD today, noticed my trans on a long drive hovers around 120f, when oil temps get up to 220f, where they should be more or less.
I want to replace the heat exchanger for the transmission, assuming the thermostat is dead (open) because I would imagine the transmission wants to be around 180-200f?

What is the part#? I see some places mention JUST the thermostat part of the cooler. Is this a thing? or am I insane? It looks like I need to replace the entire housing, correct?

Can someone report what their trans temp is at cruising on the highway, like 70-80MPH, once up to temp?

Thanks everyone

seanjordan20

ZF states normal temps are between 175f-265f. You will start getting errors at 265f. You should be getting an error if the sensor is bad. Do you have INPA to see or test your sensor.

icantfindaname2

I would imagine MHD is looking at the same sensor as INPA, so I mean, I'm getting a temp reading and I know the thermostat for the transmission cooler is a common failure. I have a pretty strong feeling my thermostat is stuck open.

seanjordan20

I'm thinking you were talking about a trans temp sensor not the thermo. I only had an issue with leaking from the trans thermostat and replaced it. Yes you can just buy the thermostat. Look on pelican parts for your part number

icantfindaname2

Nothing on Rockauto or Pelican or FCP

Nothing on realOEM regarding a replaceable thermostat either, for the transmission fluid, that I can find.

https://www.realoem.com/bmw/enUS/sho...diagId=17_0428

I have a feeling the N54 powered vehicles have an integrated thermostat for the transmission oil.

Edit: I am seeing videos about replacing the back half of the assembly.. but.. no part numbers yet, and theyre all for stupid Euro only diesels.

seanjordan20

On yours they do not offer it separately. If you're trying to save money they have used ones on eBay

icantfindaname2

so I wanted to bump this post.

I initially thought that the thermostat was on the transmission fluid side. Some research seems to point to it being on the coolant side of the heat exchanger.

I really don't feel like spending the 300 dollars for a heat exchanger just to have it fail again, so I started digging around and found this thread, for an E61 LCI 535D. I know it isn't an N54, but, I think I can make this solution work for my wagon.

https://forum.bmw5.co.uk/topic/13244...nger-write-up/

Anyone attempted such a thing before?

edit: more reading seems to point to this not working as i think it will.. i think this HEAVILY affects the Diesel guys, as they can't get any temp in their coolant or oil with this opened, where us gas guys don't have a problem with coolant or oil temp, just transmission fluid temp. more research is needed.