GX460 Transmission fluid cooler (2 Viewers)

[thescreensavers]

Yep. That thermostat is to get the transmission fluid up to operating temp. It bypasses when temps are approaching (or have reached) target fluid temperature. Pinning it is the equavilent of removing your engine coolant thermostat to prevent an overheat. All it will create is longer warm up times for components that had nearly perfect cooling systems.

The best way to provide additional protection is to add a dedicated cooler before the return side of the loop. Many have had good results with this method.

There is no reason to put the cooler pre warmer as the thermostat will automatically regulate it to thermostat temp. I had it pinned for filter flow, will be pulling the pin so it can warm up faster now and likely will pin it again in a few months.

 

[Acrad]

I’ve had mine pinned open for 5+ years. Granted I have the smaller OEM external cooler but warmups have never been noticeably longer. My winter temps are far less extreme than some at generally nothing less than 20F for the most part. Maybe a few teen temp days here and there.

 

[rav8]

I’ve had mine pinned open for 5+ years. Granted I have the smaller OEM external cooler but warmups have never been noticeably longer. My winter temps are far less extreme than some at generally nothing less than 20F for the most part. Maybe a few teen temp days here and there.

My cooler is about twice that size I think and is probably a factor. I know when I'm pulling the camper on a long climb, it is very noticable when the stat opens. The drop from around 205° to 190° indicated on my SGII is almost instant.

I don't think there is anything wrong with pinning it, I just haven't encountered a need to. Daily driving usually stays well below bypass temp.

 

[thescreensavers]

So I've read a bit into the trans fluid temp thing. As long as the transmission is locking the torque converter then it's likely warm enough. At 160F it's locking the torque converter during cruising so I'll keep the thermostat pinned.

 

[WTITW]

Okay. Time to get a cooler.

I got both 678 and 698 to take a look. Which one do you guys think I should use? I live in AZ and rarely go into the snow. Occasionally driving in cold climates but not often. Do I really need the bypass? Isn’t that jsut to warm it up faster? If I have a bypass cooler is there any need to pin the thermostat open?

 

[r2m]

Okay. Time to get a cooler.

I got both 678 and 698 to take a look. Which one do you guys think I should use? I live in AZ and rarely go into the snow. Occasionally driving in cold climates but not often. Do I really need the bypass? Isn’t that jsut to warm it up faster? If I have a bypass cooler is there any need to pin the thermostat open?

View attachment 3833310

234º F is getting pretty warm. You must have just gone up some grades.
I know you've followed this thread, and it seams that most the guys (and gals?) on here like to keep their temps bouncing above and below the 200º F mark by about ±10º F. I start getting warm around the neck when it starts climbing over 220° F on my readout. That's when I'll usually start manual shifting.

 

[Acrad]

I don’t know the specs on those two Hayden models but I would go with the one with highest cooling capabilitiy

 

[thescreensavers]

Living in Arizona id get the biggest one you can fit. 235F pan temp? Id get a few drain and fills going too.

 

[WTITW]

They're both about the same and both the size that Hayden recommends. Both are twice as big or more than OEM.

What I'm not sure about is whether to use the one with the built-in bypass that opens at 180° and pin my T-stat open or the normal one that does not have a bypass and keep my T-stat operating.

@Acrad Is there a benefit to keeping the T-stat open other than lower temps? Does it increase flow or just re-route? Doesn't it open at 170° so not that much different than the cooler with the bypass built in.

@thescreensavers Yeah, I plan on doing a flush after. I know everyone is scared of flushes over 100K but mine did fine at 160K and shifted better after. It's also what Toyota and the LC shop I use for some stuff recommend, so I think I'll keep doing it. If it explodes this summer, I'll come back for the "I told you so's" : )

 

[thescreensavers]

They're both about the same and both the size that Hayden recommends. Both are twice as big or more than OEM.

What I'm not sure about is whether to use the one with the built-in bypass that opens at 180° and pin my T-stat open or the normal one that does not have a bypass and keep my T-stat operating.

@Acrad Is there a benefit to keeping the T-stat open other than lower temps? Does it increase flow or just re-route? Doesn't it open at 170° so not that much different than the cooler with the bypass built in.

@thescreensavers Yeah, I plan on doing a flush after. I know everyone is scared of flushes over 100K but mine did fine at 160K and shifted better after. It's also what Toyota and the LC shop I use for some stuff recommend, so I think I'll keep doing it. If it explodes this summer, I'll come back for the "I told you so's" : )

I'm in South Florida but I installed a 678 runs at 160s cruising down the highway 70F outside.

Thermostat line is bypass flow, its typically not even open until the thermostat opens. Pinning it just keeps fluid cycling. This can be beneficial especially if you have an external cooler or inline filter which I do in my GX.

Fresh fluid is best doesn't matter the mileage, what gets you into trouble is sending crap through the valve body.

 

[rav8]

They're both about the same and both the size that Hayden recommends. Both are twice as big or more than OEM.

What I'm not sure about is whether to use the one with the built-in bypass that opens at 180° and pin my T-stat open or the normal one that does not have a bypass and keep my T-stat operating.

@Acrad Is there a benefit to keeping the T-stat open other than lower temps? Does it increase flow or just re-route? Doesn't it open at 170° so not that much different than the cooler with the bypass built in.

@thescreensavers Yeah, I plan on doing a flush after. I know everyone is scared of flushes over 100K but mine did fine at 160K and shifted better after. It's also what Toyota and the LC shop I use for some stuff recommend, so I think I'll keep doing it. If it explodes this summer, I'll come back for the "I told you so's" : )

A bypass on an added cooler would just introduce another potential failure point IMO. A quality cooler of the same size or larger than the external OEM (Canada?.. @Acrad ) should do great for towing your camper.

I think the t-stat opens at the 190° +/-5 range. Thats when I see temp drops upon opening.

Edited to clarify I am talking about the optional (non-US market) external OEM oil cooler.

 

[Cold Iron]

They're both about the same and both the size that Hayden recommends. Both are twice as big or more than OEM.

What I'm not sure about is whether to use the one with the built-in bypass that opens at 180° and pin my T-stat open or the normal one that does not have a bypass and keep my T-stat operating.

@Acrad Is there a benefit to keeping the T-stat open other than lower temps? Does it increase flow or just re-route? Doesn't it open at 170° so not that much different than the cooler with the bypass built in.

@thescreensavers Yeah, I plan on doing a flush after. I know everyone is scared of flushes over 100K but mine did fine at 160K and shifted better after. It's also what Toyota and the LC shop I use for some stuff recommend, so I think I'll keep doing it. If it explodes this summer, I'll come back for the "I told you so's" : )

Seeing how you are in the Valley I'd pin the factory bypass open all year and use the 678. If it were me.

The factory bypass just reroutes it does not increase flow. Well except from zero to full when it is open. Lot of speculation as to when the factory T stat opens mine is closer to 200° and the Hayden 698 is supposed to be 180°

This time of year my factory bypass doesn't even open very often. Typical 14° above zero day after 10 minute warm up and then 20 minute drive to town for beans and beer.

I went with the 698 because of where I am at. Many in the North have had to tape cardboard in front of the Hayden during the winter to help increase temps. I don't want to have to do that.

I will pin the bypass open during the summer and release it after that. But that is a crap shoot it might be 60° one day and in the twenties with a blizzard the next day. So the Hayden with the bypass will help with that if I still have the factory warmer pinned open.

In a couple of years I could see myself spending winters in Sierra Vista\Huachuca City area. No way I could see living in the Valley with all the growth and population explosion even though the hospital is up in Scottsdale. I will keep the same setup. But if I lived there all year I'd skip the 698 and run the 678. There is more than some truth to what rav8 says about complexity and architecting highly available systems and disaster recovery I will say you can get too complex and introduce failure trying to get too fancy. On the other hand spending 20 years working with mechanical systems the Hayden bypass is very simple, about as simple as you can get



I only tow 2,500 pounds on occasion. I hit 240° once and there was no grade involved. Road construction headed into Canada in September (~60° ambient) with stop and go traffic for 15 minutes. If you aren't moving the temps on the tranny climb fast and once the sump gets hot it takes awhile to cool down. Stop and go traffic in a city can be as bad if not worse than towing up a grade.

If @Acrad can run the bypass pinned all year with the OEM cooler in the PNW I'd do the same where you are with the 678. If you have any doubts at all then use the 698, but my goal is to keep the ATF in the sump cool and prevent it from getting so hot that it struggles to cool back down. I don't think you can go wrong with either Hayden but I'd pin the bypass open either way. In your case.

 

[xychromosome]

Recently pinned my thermostat and have seen lower temps. I’m using the OEM cooler and I frequently see temps over 200 even in highway driving, Dropping to the 190s which lends credence to the thermostat not opening until it gets pretty hot, 190+. With the thermostat pinned, my temps are pretty steady at under 180. So I’m assuming that the cooler is not receiving flow until the thermostat opens and if it’s pinned, it received flow from start up, correct? If so, I’m happy to keep it pinned. Will continue to monitor temps especially in driving Harder on the tranny, eg at the beach

 

[Cold Iron]

Recently pinned my thermostat and have seen lower temps. I’m using the OEM cooler and I frequently see temps over 200 even in highway driving, Dropping to the 190s which lends credence to the thermostat not opening until it gets pretty hot, 190+. With the thermostat pinned, my temps are pretty steady at under 180. So I’m assuming that the cooler is not receiving flow until the thermostat opens and if it’s pinned, it received flow from start up, correct? If so, I’m happy to keep it pinned. Will continue to monitor temps especially in driving Harder on the tranny, eg at the beach

Correct. The thermostat when pinned open allows ATF to complete the full loop through the transmission cooler

Normal operation with it unpinned does not allow flow through the cooler until the temps are high enough that the poppet valve opens from heat. Until it heats up it is in recirc (recirculation) mode, it doesn't go anywhere except through the warmer then back to the sump.

Most lubrication and heat exchanger systems use the same 3 basic flows. Suction, discharge and recirc. Based on heat transfer and fluid flow.

Back when papers and forms were common instead of computers with email and forms we used to have baskets on our desks for the paper. Most people had 2 baskets labeled Inbox and Outbox. I had 3 and they were labeled suction, discharge and recirc. If I put your paperwork in the recirc basket it wasn't going anywhere fast. Eventually it would end up in the circular file (trash can).

Pin the T Stat on the warmer open and your ATF will flow through the cooler. From the moment you start your engine.

 

[WTITW]

I used the Hayden 698 bypass cooler. Went good but took forever. Mostly my fault. I cut the hose in half thinking that would be fine but the one routed to the return hard line at the bottom was about 1” short. 1” = $32.95 and an hour finding and getting it .

Big thanks to @pacard17 came over and helped with the fun. I didin't film it but took a lot of pics. We use 2" aluminum angle and 2" aluminum bar (1/8") to make three brackets. Tied into the Upper radiator support where one of the horns was, and the center apron was supported in two places. Relocated horns and such to the center support as well. Used grommets on both the cooler brackets and the trasncooler.

A few notes: Found it easier to remove lower hose clamps by removing the hard line brackets that run under the front cross member. Also, should have listened to Paul and dipped th hoses in hot water for a 30s instead of try to wrench the hose onto the cooler with my hands... for 30m, until my hand had a bruise. Used hot water on the replacement hose and it went on in 10 seconds. Typical Jake s*** ; )

All hardware is m6 various lengths (get a kit like this) and locknuts.

Install location with horns removed. Used right hole for z channel mount made from 2" aluminum bar.

Upper L side (driver) mount from 2" bar bent to purpose - We just marked and cut / bent freestyle, sorry no measurements.

Upper R side (passenger) mount. This one we made with a 1" cut of 2" angle, then we bent one side to make the Z

Lower center mount from 2" angle (trimmed to 1x1 on the short side). I forget what the center grommet size was but I used one the same size on both ends that fit snuggly through the hole pictured. Any Truevalue or Ace...

 

[WTITW]

Mounted Upper passenger mount to the hood latch screw which already was grommeted. Added a flat rubber washer between the mount and bolt washer.

Grommets and 20ish mm M6

Upper L side mount installed with flat rubber 2" washer

Upper R mount with horns re-attached. Drilled a new hole in the cooler flange to accommodate;

Fully installed cooler;

Added a 2nd hole lower down for more purchase.

 

[WTITW]

Plumbed lines through the shroud and then two existing holes with foam pads in radiator support;

Made 3-4" heavy loom sleeves for where it passes through the radiator support. The foam was falling apart and the hose would rub against the metal if not. Added braided loom to the entire hose. I use Tesa Tape to protect the edges and clean up loom;

Bottom hard line to trans return (lower cooler hose to this). Mine had the clamp facing the radiator shroud, and I could not get a needle nose in there, so I unbolted the hard lines. There are hoses on the other end of the cross member, so they're pretty loosey-goosey after, and you can drive a truck in there to get the clamp. I used hose clamps on the cooler and OEM clamps on the truck's side of the equation.

Here are the hard lines I unbolted to get better access to the clamps on the bottom.

I didin't take pics but we filled the cooler and hoses with ATF fluid making sure to leave as little air as possible before plumbing in. Then we used two M10 bolts to plug each hose while it was loaded up. Next I removed the upper hose and lower hose and connected it. Not much drama there, I used hose clamps to ensure minimal mess on the hose we removed (small u shaped hose from OEM cooler outlet to trans return hard line). I used GX Bob's video as a guide for this. Zero need to remove the bumper like he did though. Maybe thats relevant on a 14+ but we just removed my grill and that's it.

Hope this helps!

(not sure why I can't delete this last orphaned image; in the meantime, enjoy another view of my well cared for hose : )

 

[Rogue556]

I've been looking to add a cooler to my 23' since I picked it up a little over a year ago in December of 2023. Reading through all of the different threads here and elsewhere, it seems most are running the cooler after the radiator but very few are bypassing the radiator all together. I can't figure out why one wouldn't just bypass the radiator all together with the factory thermostatic switch 'heater' on the transmission pinned open, then simply run an aftermarket thermostatic switch before the external cooler, and simply us the temperature of your choosing instead of relying on the factory switch (which seems to open too hot as it is). Bypassing the radiator seems to make a lot of sense if you are adding a much larger aftermarket cooler in place of the poor performing "cooler" built into the radiator anyway, right? In the winter with ambient temperatures at or below freezing, I typically won't see the engine temperature reach 130 degrees until the vehicle has idled for 10 minutes or longer anyway, so I really don't see the radiator playing much of a factor in warming the coolant, either, unless I'm missing something?

Below is the route I've been looking to go on mine.

A lot of the folks on CorvetteForum and many of the other racing-oriented forums seem to be having great luck running an inline transmission/engine oil thermostat in conjunction with a large trans cooler. Improved Racing and Derale both sell quality options that many have used with great success.

Examples:

Improved Racing seems to offer a few options that I think would solve a lot of issues, and they have plenty of temperature options to pick from.

This is their "compact" version that flows up to 5 GPM. They also have a larger version that flows up to 20 GPM. Based on my phone conversation with one of their employees, the 5 GPM should be perfect for the use case we're talking about.

Their inline thermostat also keep fluid flowing to the cooler at all times, even in "bypass" mode. It lets a small amount through to insure there are no air pockets in the cooler, which is an awesome feature.

This gives you an idea of what temperature ranges you can choose from, and they also make rebuild kits so you can easily swap the internals for a different temperature, should you need to. I'll likely give the 165-degree option a try first, since it states that it allows full flow to the cooler at 181 degrees, and I'd prefer to rarely get above that temperature.

Is anyone running a similar setup to the above and bypassing the radiator all together?

 

[Rogue556]

(Continued)

They also make a version of their thermostat that includes a spin on filter mount as well. Honestly, it may be overkill, but I think this is the route I will go If I can find a solid place to mount it. (I'm thinking somewhere in front of the radiator support and behind the bumper/crash bar on the passenger side). Paired with a Wix 51269 filter, which filters down to 10 microns, has an 8psi bypass valve, and has a max flow of 7-9 GPM, it would do well to keep the valve body clean. Change the filter every 30k miles with a pan drain/fill and you are set.

The filter mount with thermostat functions just the same as the non-filter version. Also, it too can be rebuilt with any temperature you want and allows a small amount of flow to the cooler in "bypass" mode to prevent air pockets.

They also sell a cooler that is similar dimensions (Length and Height) to the popular Hayden models, but over 2" thick and holds 1qt of fluid and has an optional fan shroud for use with a 9" fan (should you want to go that route).

Obviously, this setup isn't for everyone, and it's not cheap. (All in all probably close to $1,000 if you buy an aftermarket bracket to make it fit) but I don't think you'd ever have to worry about transmission temps again with a setup like this.

 

[thescreensavers]

(Paired with a Wix 51269 filter, which filters down to 10 microns, has an 8psi bypass valve, and has a max flow of 7-9 GPM, it would do well to keep the valve body clean. Change the filter every 30k miles with a pan drain/fill and you are set.

Adding a filter is a great idea, if you would be using a hydraulic filter id also add 10-20 of these guys BY042SH | 2" Len x 1/4" Wid x 1/8" Thi | Neodymium High Temp Block Magnet | K&J Magnetics - https://www.kjmagnetics.com/by042sh-neodymium-high-temp-block-magnet on the outside of the can.