There's a lot to read here to understand the differences between 3 or more coolers and which tradeoff is best... or worst.

I would like to know both how important a thermal bypass is, either in the trans cooler plumbing (many newer trucks/vehicles, especially diesels) or inside the actual cooler (Hayden's patented design) in Northern states (Northeast/upper Great Lakes/Canada) and are the external bypasses that are OEM installed dependable. I see cool looking billet bypasses but after dipping deeper many seem to intentionally defeat the purpose and run all the time, one way or the other. The performance bypasses are designed to work at a preset temperature. The Hayden coolers are internally designed to let smaller qty of fluid through only selected passages until the temp warms and the viscosity thins (I think.)

My holdup is deciding which cooler to use and if it has hose barbs or AN fittings. Hayden's #697/698/699 models are the only 3 using this design. Their #699 is otherwise identical to #689, but the 689 has NO bypass feature BUT it does have 6AN male threads, whereas the 699 has just hose barbs BUT the thermal bypass feature. They also have a #779 which has 7/8-14 female threads and are thick like the B&M coolers. I'm trying to decide between the 689 without bypass but with 6AN outlets, the 699 with bypass but just hose barbs, or the 779 without bypass but with female 7/8-14 threads. The one WITH the patented bypass is the lowest cost, about $55. The most expensive is the 779, about $85; the 699, I'd try modifying it to 6AN.

So how important would the thermal bypass or lack of it be in a multi-use, multi-weather vehicle in the North? All are the latest plate designs. The 699 & 689 are both 30 plates. I can also get a 30 plate thicker model for about the same price as the 699 but they don't have any with built-in bypasses yet. (most are made in China anyway, and the tech guy at Hayden didn't know about the 6AN models) Maybe I should start a poll?

Any Help would be appreciated.

 

Again, you are thinking WAY to hard about this. You dont need a by pass. Get one that you can afford, mount it, plumb it, and go

 

Matermark, have you considered installing a cooler with NO bypass, and just covering it with cardboard during the fall and winter?

 

How about not using a cooler at all. Just use the intank cooler like MILLIONS of vehicles. If you are not towing or racing you really shouldn't need one. Don't get me wrong I think a cooler is a good idea, but not mandatory. I drove my truck all last summer with no external cooler, guess what? It never went over 190*....

 

...we like to make things difficult around these parts

 

what kind of transmission is it and what are you using the trans for (racing, towing, street/strip)?

 

.....lol dont even try asking this

 

 

Never thought of blocking the actual cooler, though I have seen grille covers in winter but on bigger trucks. It may be difficult getting at it if weather changes. I'll consider this though, especially if I run it thru the radiator--it would be like an auxiliary cooler was never installed.

To all, my problem with the in-tank cooler is the vehicle ran w/o fluid and would need to be flushed or blown out... but I am a proponent of using both in series... I was thinking of first bypassing the rad cooler if I put the new trans in, using the external only until I can clean the original one; if I am just doing lines first and running around without 3rd/4th then I'd wait on installing the external cooler.

I am just surprised I didn't hear anything about the thermal bypass cooler, has anybody else? You'd think they'd be selling like hotcakes in northern states/countries. When you do searches the hits are lots of complaints about, or modifying the OEM external bypass blocks to convert to an always-on to lower temps. I didn't even know they've been used from the factory...Also, I didn't know Hayden has a patent on theirs.

 

@theunderlord
So I see your sig has lots of diesels... do they have trans cooler bypasses, and have you done anything or had to remove/replace any?

 

It's an overbuilt 4l60e in a 5300lb alum V8 XUV/SUV 2WD/4WD 90/10 street/strip, on/off-road, occasional tow/hauling...

 

10% strip, so you're going to take it there 36.5 days per year. up here in winter land our tracks are open 5-6 months out of the year. that works out to about going to the track once every 5 days. yet you don't have money to buy a $15 fitting....

 

One was an Alison1000 that was just fine with zero mods other than the PPE stage 5 kit I installed in it, the other was a 5 Speed NV4500 that I actually welded in a transmission fluid temp bung and gauge in the PTO cover.

Is manual gearbox fluid temp knowledge important? Not really. Was I 21 years old and had more time than brains? Yes. So I get it, dinking around with stuff is fun.

But I'll echo what others have said, don't over think stuff too much, just get out there and have fun with it. As the last two plus years have shown us, life is short.

 

Up here? Where are you?

You are assuming 36.5 days based on 365... now change the 365 to 180, or 6 months max... that's 18x. We have a local eighth and 2 quarters within a couple hours... but all those cost money to watch or to participate.

We kinda have a 3rd mile track here a couple nights/week. It/s called the expressway. Blocker cars with 4-ways on come to a complete stop in all lanes in one direction, blocking all traffic 🚥 in that direction, with the 2 cars that are racing in front of them. Kinda like "Street Outlaws" but more adrenaline... and cop chases. Spectators watch from an overpass, which is the finish line, then scatter. Admission is free.

That money I saved on the fitting pays for food, or car insurance, not racing. But I can't walk/stand now so count me out this year. But I have in the past had a 115lb GF drive for me at the eighth track and she has won.

 

Facepalm