Got my cooler in today. Kind of a pain to route the new hoses. I removed the radiator overflow tank to get a little better access. The hardest part was getting that edge protector stuff in the access holes. I added a half quart of WS through the return line to make up the minor amount I spilled and the volume of the cooler and hoses.

I need this but concerned about pressure reduction due to additional loop, any long term issues?

I had a 2005 SR5 for 13 years with close to 250,000 miles or maybe more. It had a similar cooler I installed. The Trans never needed work even though I often towed a heavy off road trailer

Many vehicles have a secondary cooler from the factory without issues. My 2010 Tacoma had one.

Thanks, all, for sharing your experiences. I'm going to order one for my 2021 ORP.

Was there a conclusion on whether the bypass version of the Hayden cooler is useful on a 5th gen? There are several posts indicating that the tranny has an internal thermostat, which would suggest that the bypass is unnecessary. I'd rather not have the bypass if it isn't helpful as it could restrict the flow and is one more thing that could break.

the bypass on the hayden is passive, it doesn't restrict fluid flow. I honestly don't think it does much.

I ordered one of these kits with the 698 and just got mine in. I was wondering if there is any consensus on where the best place to tap the lines is? I am thinking after the OEM Radiator pass through before it goes back to the trans.

i tapped mine near the top, which i found the easiest.

Did you use a barbed fitting to connect to the OEM hose? or did you eliminate the OEM hose by connecting the cooler in between?

I was thinking of connecting one end to the raidator outlet and the other to the hardline going back to the trans

This is what Hayden says on their brochures (but doesn't offer any tech data about "colder climates").

"Hayden’s new patented internal pressure by-pass coolers allow the vehicle’s transmission to reach optimum operating temperature quickly by routing the fluid through the by-pass channel of the cooler until fluid temperature increases. This new design allows vehicles in colder climates to reach proper operating temps faster which improves fuel economy and helps reduce friction of internal components. Hayden’s internal pressure by-pass design incorporates an integrated valve that eliminates the need for external valves and additional plumbing at installation."

I also wonder if the "valve" is a moving metal part or if it is all viscosity based.

Are there any tests to show the Hayden bypass doesn't work? I suspect the key is determining at what temperature point the Hayden cooler's "valve" activates. Probably somewhere below 160 degrees as Hayden's web site frequently refers to 175 degrees as a normal temp.

Maybe there is a way to run some cold weather drive tests and find what the Hayden is doing. Would we also need to know where the temperature sensors are located in our transmissions in order to better evaluate and understand the readings on the ScanGuage?

Did you completely bypass the OEM cooler in your install? If the bypass does work properly I am guessing that would be optimal to maintain lower temps.

sorry, when i was commenting earlier i was referring to the b&M version of a bypass which is 100 percent viscous related. I'm just guessing, but on the hayden how it works is as the fluid heats up and looses viscosity, it "leaks" through the valve. Therefore the valve is probably fully passive too.

So when i got my b&m supercooler, i found out their bypass was just different sized tubes to control viscosity as air temperature passed through the fins (hence why i said it was passive). I guess when i meant "gimmicky" is more towards the marketing perspective. If it wasn't for the marketing, nobody would have cared.


IMHO, buy whichever manufacture is on sale or works for the bracket you purchased. I went with b&m cuz it was on sale but would go with hayden if i wasnt a cheap skate bastard at the time.

I used a barb firing to connect the OEM hose to the tranny hose and the OEM clamp thing on the hardline. Its the line that is close to the windshield washer fluid spout.

I basically followed the diagram that has been floating around this forum for years.


I didnt bypass the OEM radiator/trans cooler, so i'll never have a over cooling issues.

Only advice i can give, is buy some extra 1 inch hose to slip over the hoses that are touching really sharp edges near the radiator support if you are going to run the hoses near the top of the rediator or headlight area. You don't need much only a few pieces.

These 5th gen trans cooler kit sales have been picking up with more and more of them going out the door everyday. Thanks guys!