I recently rebuild and modified my 4L60e I have in my LT1 car. The build went really well, outside of the brake switch that wasnt allowing TC lockup. Now that that is fixed I have been enjoying driving the car and learning its new shifting habits. I also added a B&M TC w 2000 rpm stall. Overall im really really satisfied with the mods I made and the performance that i gained.

This past weekend I drove this car. It was pretty hot, ~90 degrees or so. This particular car I have not managed to change the fan strategy so the fans are on the stock 228* setting

So, when I am sitting in traffic the coolant temp starts to rise. It goes up to 230, the fan kicks in and temp reduces to ~200 - 195*. Well I noticed that when the coolant temp reaches 230* it takes the transmission oil temp with it. But the trans temp does not reduce like the coolant does. It will stay about 220 - 215* after the coolant cools to under 190 and even 180.

So I need to add a new oil cooler for the tranny. Trying to decide whether to add a cooler in series with the radiator oil cooler in the front of the a/c condenser, or to eliminate the radiator cooler and add a big cooler with a fan in the spare tire area.

What I am confused about is, we all know C4s have a stupid stock fan strategies and many change this setup either by adding larger radiators, wiring in fan switches, adding new fan relays, etc etc. But what about the owners who dont do this? Do they actually drive around with tranny temps above 220*?? This seems improbable but I have had 3 c4s and ALL of them ran hot (200+ deg) until I made mitigating modifications. This is my first A4 vette so this tranny temp issue is foreign to me. So unless mods are made, your tranny will run 200+ degrees??

 

Just put a tranny cooler in front of the condenser and you'll be fine. I bypassed the radiator and use a B+M stacked cooler for my 4l60e.

 

okok. Do you mind letting me know which one you are using?

I have both of these in my Summit shopping cart, trying to figure out which one will be sufficient:

This one with 48 rows:

https://www.summitracing.com/parts/bmm-70274/overview/



of this one with 36 rows:

https://www.summitracing.com/parts/bmm-70266?rrec=true

 

Terrible thread title

 

It got you here.. lol

 

I'm using the smaller of the two.

 

I went with the B&M 70264 on mine. It's small, but gets the job done. Keep in mind I'm not drag racing the car, so I don't need as much cooling. I also need to balance out cold morning temps with hot afternoons. I plumbed it inline with the stock cooler. I kept getting high temps(230+) when going uphill on my commute, and now even on a hot day, it rarely goes over 200. It cools down much quicker too, once I've crested the hill and back on somewhat level road. I haven't tested it over 90 degrees yet, but I will soon. The real test is going uphill on a mountain road on a hot day, stuck behind a line of ****** tourists that peak at 25mph, and slow down to 15 for most corners.

And yes, even after a new t-stat and complete coolant flush, the tranny was always hitting 220+. Going up hill it would get as high as 260! Would take forever too drop too. That was making me cringe hard watching it hit those temps, lol.

 

Everything I read online suggests that at 250+ degrees you are causing damage to the tranny. More specifically, varnish forms, then seals next. So I am certainly in the same boat as you, looking at these temps and fretting big time. Which brings me back to my original quandary, that Chevy sold these cars knowing the tranny temps could be 250+ during normal non-racing usage?? Something seems wrong about that.

 

"that Chevy sold these cars knowing the tranny temps could be 250+ during normal non-racing usage??"

I forgot to mention that I changed the fluid to dex 6 as well, which helped a lot. I think so many C4's end up with overheating trannys is due to really old fluid that's never been changed, not due to Chevy dropping the ball. I'm sure when these cars were new, they never ran that hot. But after 20+ years, and lots of miles, that fluid is done for. Fresh fluid, plus better fluid = lower temps. I've never bought a used car that didn't have old and worn out tranny fluid. Almost nobody changes that, regardless of what the manual states or how many miles they rack up.

I also got a pan with a drain plug, so I can at least drain and fill the fluid in between filter changes.

 

Change it's name from Bruce to Kaitlyn it'll cool off real fast

 

 

Please elaborate on how you can tell when the fluid is "worn out"?? I am curious.

 

220f tranny temps with a quality synthetic fluid is nothing to worry about, also i'm sure back in the day of c4 engineering this kinda of temp is what made them choose the fairly short ATF fluid change cycle. Although I'd like to see 170f temps like in my 1 ton tow rig tranny i don't so I just change pan fluid (3.5qts) every time i change motor oil, keeps the ATF fresh red+clear.

 

The transmission and converter builders I know for decades never seem to recommend synthetic transmission fluid. I'm actually not sure why - its one of the few mysterious things I've encountered over the years. Maybe thats changed, I dont know.


I've rebuilt a fair number of 60e/80e units and the ideal operating temp seems to be 167*F to 188*F. At least for my region (ambient temps in the 90's and high humidity).
Use as much cooler as it takes to hold this temp range. Use a fan if needed. Use a aux fan controller if needed.

On my 80e I had to assemble a home-made fan controller using arduino because the OEM ecu has no fan for the transmission to come on.
its pretty simple and would work as a temp sensor and fan controller for oil temp or trans anything really


You never want to see 195*F+ Trans temps in a 60/80e. Its not like an engine. I feel that trans fluid doesn't tolerate high temp well and the viscosity drops a bit too much considering the spaces between parts and the necessity of its interaction with the paper of the clutches - things happen inside a transmission which are far from in an engine and the high temperature acts in an unfavorable way towards almost every aspect of it. If it wasn't for driving away the water it would probably even be happy at 120 to 140*F to be fair.

Keep in mind because temp adjusts viscosity it also changes shift pressure so the transmission tuning must be generally dont using a mechanical pressure gauge if you've modified the transmission in almost any way and tuning should be done at every temperature to restore its baseline values. Some mods like the lube to line have a large impact on idle and low pump rotating speed pressure values.

 

Thank you for posting such a complete schematic. I'm reading what looks like "ov" in your diagram as zero volts, I hope that's correct.

I am curious, from a functional stand point, what does this do better than a temperature switch and relay? For example have you programed the Arduino to run the fan for some time after the temperature switch opens? Or is that a temperature sensor? Or is its driving of the LCD readout the benefit?

Is the "VCC" constant hot, or switched (key on)?

 

there is much more control and safety using an arduino to control something like fans. For example if the fan doesn't get power your arduino can warn you by checking the fan wires for power and setting a LED or alarm buzzer if the fan should be on but power and or ground is not being detected. The temperature calibration is entirely up to you making it potentially extremely accurate steadfast reading for coolant oil trans fluid, replacing and or sanity checking other gauges or sensors. Since arduino can throw some transistors easily it functions as many switches on many outputs all for automotive relays which can control almost anything in a car and read information back.

The power should be provided by a small power supply rather than car battery direct and with an inductor to limit current spike from voltage spikes. I didn't draw in any transition voltage or flyback diode components which should be used in automotive apps for these type of projects.

VCC is just how the LCD labels one of its power inputs. power can be switched or constant - for this I assume you'd want it switched on with the key like typical accessory. It was meant simply to be consistent with labels rather than 'vcc' as a general term. 0v is indeed a ground in this but 0v is not always a ground symbol I Just mean for the sake of this project the ground level is sitting at what should be 0v with respect to the car electrical system in order for the transistors and automotive relays which are pulled by car battery to work properly.