Hey everyone,

I just about completely drained and refilled my E40D and added an external cooler and a gauge setup. The cooler is mounted after the radiator cooler and the gauge sending unit is mounted in the test port on the driver side of the transmission, just above the pan. I installed a Tru-cool low pressure drop cooler that supposedly is self-regulating. Fluid that is too cool and viscous only passes through the first two plates, and after it becomes thin and warm, it passes through the rest of the cooler. That's what they say, at least. I had installed one of these on a previous vehicle and had good luck, so I figured why not.

Well, I over did it. The transmission now wants to run at a whopping 130-150 degrees. I got it to around 165 once, but I had to work for it. I'm glad it's doing such a good job, but isn't this too cool? The shift points all seem to be correct and it doesn't have any trouble with going into overdrive. As a matter of fact, it shifts better at 130 degrees than it does at 150 degrees. A little more smooth and direct.

Should I consider installing something like this?


I was thinking that I was doing something good by keeping it cool, as the more in town driving I do and the hotter everything gets, the crummier the transmission shifts. I'm a little worried that I'm doing more harm than good now.

Dan

 

I don't think you are harming it. That's a bit on the cool side, but not too bad.

There is a post in the Excursion forum about a similar thermostat. It worked fine in the winter, keeping temps around 160-170. But when hot weather came temps were usually over 200. It seems (I don't have definitive proof) that the 3/8" thermostat is too restrictive. There was a 1/2" model available, but nobody had tried one of those.

 

Hey Mark,

Thanks again for the help. Maybe you can answer another question for me. How long does it typically take for an automatic transmission to reach a normal operating temperature? My commute to work is only around 6-7 miles. I make very few stops, most of it is freeway driving. I would imagine it takes longer than this for the transmission to reach a proper temperature. I noticed this morning, for example, that it reached maybe 120 degrees when I was a half mile from work.

The transmission seems to shift well, however the 2-3 shift is a bit soft and slow for my liking. I noticed today that when giving it 50+% throttle up a hill, while accelerating from a stop, it definitely hesitated a bit in between 2 and 3. It didn't climb rpms while it was shifting, however it did take it's time, which bothers me a bit.

Also, you helped me earlier in another post about me complaining about a rough shift from 1-2. To follow up, I replaced the shift handle, which fixed the inoperative overdrive off light. I haven't seen it blink yet, so I figured I'd wait until it started blinking until I take it to the dealer. The batteries have been disconnected since the last rough shift episode, and it's been so long since, I feel like I would be bummed if I payed the dealer for a diagnostic and they couldn't find any codes. For now, maybe I'll cross my fingers and hope it just needed a service.

Dan

 

It takes a while to warm up the trans. There is no thermostat so the cooler is always cooling. And there is no combustion like an engine. Highway driving is the slow way to warm the trans, so what you're seeing looks normal to me.