Tru-Cool Max 40k Transmission Cooler

[Matthew Jeschke]

I'm having a horrible time with this dumb cooler. The cooler I shouldn't pick on as much as the thermostat. It's got me ready to rip it off and throw it in the garbage. My trans runs SUPER cold. WAY too cold. I bought the thermostat which came with no fittings, and no instructions. Everybody on internet is installing JUST the cooler so I cannot make much headway.

Here's my problem...

Thermostat has what looks like a 3/8" push connect fitting but isn't. There's no lip on it to go with the sealing oring in a push connect nut. See image...

Next I have to find a MESS of fittings to go from a 5/8-18 male hose nut, to a 5/8-18 male quick connect even if I could figure that out... I don't think it'll work with a quick connect...

What on earth is that garbage fitting they have on the thermostat there? How do you best interface with it short of a rubber hose and hose clamp?

I'm almost ready to throw this thermostat in the garbage. I saw one tutorial, the only one where a guy used a thermostat. He used this one but it's $200

High-Flow Engine & Transmission Oil Cooler Thermostat

Improved Racing's Flow Series Motor Sport (FSM) oil thermostat is a universal solution that can be used with any oil cooler on any vehicle or industrial application flowing up to 20 GPM (75.71 LPM). Trusted by professional race teams, OEM's, and military contractors. Accelerates fluid warmup...

www.improvedracing.com

Has fittings that make since. Oh and I cannot seem to get any tech support from tru-cool. Has anybody ever reached out to them before?

 

[Mudsport96]

Sorry man wish I could help, but I have not used one of these before.

 

[gooffeyguy]

Is your trans still plumbed through the radiator, then to the Tru-cool?

The fittings on that thermostat look like just a barb fitting used with rubber hose and a clamp. Don't use a worm gear clamp, it'll leak in winter. Use a spring clamp.

 

[Matthew Jeschke]

Is your trans still plumbed through the radiator, then to the Tru-cool?

The fittings on that thermostat look like just a barb fitting used with rubber hose and a clamp. Don't use a worm gear clamp, it'll leak in winter. Use a spring clamp.

Yeah I kept the radiator cooler connected. Somebody told me and I didn't know any better, that I'd not need the thermostat because I'm going through the radiator cooler.

I'm throwing that tru-cool thermostat away. Cooler is getting to be a bit of a money pit That said, guy who sold it to me just gave me my money back. Was a bit shocked. I bet it came in a kit and he didn't want to use it either.

Called summit racing Derale makes an oil thermostat that is MUCH better than that tru-cool one. It is also the same price It uses threaded fittings to connect line set. $120 for all the fittings, line, & parts.

Pardon Our Interruption

I bought 25' of aluminum hose so I can also do away with the line couplers and have a solid piece of line. I could have used AN hose but I like the metal line better.

Then he sold me fittings to put on the thermostat so I don't have to use a flare tool for the thermostat side... I think with that nice bracket included in kit I can mount the thermal bypass on the underside of the core support behind where the clip was originally for the line set OR right where the line set clip on the core support is. Then bend new lines from the thermostat to the cooler.

Should turn out pretty slick. What might be even better but I couldn't find a solution for the 4L60E is the thermal bypass they put on newer 6 speed automatic transmissions. Those clip right into side of trans case then line set goes out from them. Unfortunately, I couldn't find one for a 4L60E. And unsure if dimensions are same to fit a 4L60E. That would be SUPER slick, factory solution. Then they sell kits to make them more robust. I guess the factory can tend to fail from time to time so there's a few aftermarket rebuild kits to address the factory issue.

I think this is one thing I definitely need to do a video tutorial on trans temperature & thermostats when I get time. I spent forever scrolling YouTube trying to get best ideas for installing the thermal bypass. Seems everybody is on mantra throw the thermostat away, as cooler is better. Only two guys talked about thermostats. Everybody else just says colder the fluid the better.

 

[SnowDrifter]

Out of curiosity, what's your plumbing order for the cooler + radiator pass through, and what sort of temps are you seeing? Mine settles in around 100f on cold days, order is cooler, then radiator, then back to transmission

 

[Matthew Jeschke]

Great question, I couldn't say, I need to trace the lines. I had really thought it was trans, radiator, cooler, then back to trans but honestly, I've never traced it.

My temps are 100F to 120F. Ambient ranging from 45F to 75F. I think in summer when it's 115F cooler would be fine more or less. If it rains, then of course cooling efficiency is much better and I get down under 100F.

Couldn't help but notice.. in your signature "Original 4L60e god help me"... It should hold out fine, so long as you don't have a check ball pass through the separator plate. I'd swap those with the Sonnax plastic ones next time you drop the service pan. You can throw a boost valve in the pump at the same time and pin less accumulators. I think GM fixed addressed failure points in case such as a hardened sun shell by then.

 

[SnowDrifter]

Right on

Honestly I'm not sweating about those temps. Sig needs to be updated. I'm just shy of 185k with the original trans.

Just kind of a cheeky jab since I've seen them go out around this time. Actually iirc don't they like to conk around 160ish?

 

[Matthew Jeschke]

Ah gotchya, I was running my original 4L60E up to 240k miles, when I swapped with another I built up. Never had any issues with it.

What temps you see with your Tru Cool cooler?

Did you notice a loss in MPG?

I'm also troubleshooting a 2MPG loss around the time I put the cooler on. Not sure if it's that, or something else.

 

[2006Tahoe2WD]

Dumb question - because someone already probably covered it..... Assuming the "cooler" inside the radiator is still in play, which side would you cut into to attach an additional cooler? I like the idea that when it is cold the radiator might quickly heat the trans fluid to what it needs to be.
A thermostat I like is this one that comes with 6AN fittings and can be ordered with different thermostat settings. A bit pricey ($159) but in the grand scheme of things not so much.

 

[2006Tahoe2WD]

Most routing info. I see has the hot fluid from the trans. going to the water radiator first - like this.

 

[Matthew Jeschke]

Got a thermal bypass installed. Little video below...

New video by Matthew Jeschke

photos.app.goo.gl

 

[Matthew Jeschke]

Dumb question - because someone already probably covered it..... Assuming the "cooler" inside the radiator is still in play, which side would you cut into to attach an additional cooler? I like the idea that when it is cold the radiator might quickly heat the trans fluid to what it needs to be.
A thermostat I like is this one that comes with 6AN fittings and can be ordered with different thermostat settings. A bit pricey ($159) but in the grand scheme of things not so much.

View attachment 424997

Cut into the side coming out of the radiator (liquid to liquid cooler) to the liquid to air cooler. You want to have the liquid to liquid cooler help heat up the trans to operating temperature.

It's pretty simple... splice the thermostat into the lines going to the front, liquid to air cooler. Return to transmission is the driver side hose on the cooler... the input (hot line from liquid to liquid cooler) is the passenger side into the liquid to air cooler.

Hopefully that makes since.

TIP: I recommend cutting the return line (driver side). Cut it back where the rubber ends on return to transmission. So your going to remove the entire line including rubber piece up to the trans cooler. That was a PITA to deal with that side. Then get an AN6 fitting and install rubber line to the metal hose running from the transmission. I used aluminum hose to plumb all mine up... just wish I'd had some AN6 for that little run. Feel free to PM me with any questions.

The HOT side from radiator was fairly simple to work with otherwise.

I just finished this project minutes ago.

...

That bypass in your picture was too spendy for me to warrant buying. Derale makes one, I just bought it. Seems to work, at least for first mile of driving haha... I finished installing it minutes ago.

Only big difference is it doesn't come with the fittings like that you have to buy them / adapt it to what you want to hook it to. It also appears to be a cast part body that one is machined from billet, would be super expensive to make, probably why it cost so much.

Derale has a always flow / cannot plug design feature that makes it a bit more attractive too. Not sure if that one is that way or not...

 

[2006Tahoe2WD]

Yes I follow. Do you have a temperature gauge(s) to see how the bypass modulates?
Thanks.

 

[Matthew Jeschke]

I have the cluster with the temp gauge. I'd highly recommend swapping out if you don't have one. That said, under normal duty, these transmissions are really hard to overheat w/ the factory setup.

I venture the bypass I installed won't activate until this summer when I'm out using 4wd climbing rugged slopes in over 100F temps.

I can tell though in the few minutes I tested the bypass after install that it's warming the transmission up nicely, while keeping the cooler pressurized. Prior to contrary belief a warm transmission is a happy one (150F to 200F is my target temp range)... It's the scorching hot transmission you want to avoid.

In hindsight, one of the BEST mods you can do is your coolant fans. If you have electric turn them on at a bit lower temperature... I have mechanical so I installed a heavy duty fan clutch.

 

[2006Tahoe2WD]

I'm not sure what I will do. Right now at 181k miles I baby the transmission in hopes of keeping it alive. No towing or real hot weather. Last year I drove over Sonora Pass on July 3 but it was cool because of the altitude.
At one point I looked at changing the dash and getting the odo set properly but they can't set all the numbers e.g. fuel used, hours/etc. There might be a way to add the trans. temp. I could setup my cell phone and blue tooth to watch the temp and see what happens via OBD II.

 

[Matthew Jeschke]

If you're only doing normal driving (no towing), even if you are doing light towing... There's little chance you're overheating. Your name leads me to believe you have a 2006? In which case you'd have electric fans. Likely you don't even need to fiddle with those but can lower temp they turn on if you have means, I'd probably go to 180F t-stat as well if you do that. I'm not sure if 2wd came with the liquid to air cooler (in front of the radiator). If not you could add one if you're concerned, if it's factory cooler you may not need the thermal bypass. Strong possibility factory be plug and play as well.

As far as keeping your transmission alive. Clutches & seals so long as they live in good fluid and aren't over heated, like over 225F... Then they should be fine. Somebody may correct me here, I've only fiddled with a few vehicles in my own garage. My trans had ~ 240k miles on it. Worked like a champ, I only swapped cause I wanted to.

GM worked out most of the glitches in the 4L60E by 2006. I believe factory started to put in a hardened (heat treated) sun shell along with corvette servo (or similar) on all the 4L60E builds after 2000ish, a 2006 would certainly be included in that. Only thing, I'd recommend is a boost valve for the pump, plastic check balls, and pin-less accumulators. The plastic accumulators from the factory SUCK. All this can be done when you service your transmission from the service pan.