[fbilly420]

I was under my truck and noticed that the cooler bypass tube is gone I think the PO did away with it.
Is it going to raise any concerns come winter. I just want to make sure. I have heard people having problems with them getting plugged and burn up a trans. I dont want that.
Not sure if the fluid bypasses to warm up when cold or if it is only for a plugged cooler?
Thanks
Billy
:ford:

 

[Redfish]

Unless you see sub zero temps in the winter, I wouldn't worry about it. In my climate there is no real reason for it, I plan to ditch the bypass when its time for a BTS.

 

[fbilly420]

thanks I wasnt sure and i think ill be ok in SLC utah it only gets to single digits occasionally.

 

[smorris]

I lost mine after having trouble with two in a row sticking. The original went 160,000 miles. The next two less than 10,000. Now they are installed in someones landfill for good. Since removal , no more problems.

 

[Racer X]

Unless you see sub zero temps in the winter, I wouldn't worry about it. In my climate there is no real reason for it, I plan to ditch the bypass when its time for a BTS.

You may not have an option to ditch it, unless you are removing it after you buy. Ask BTS before you do, just in case. Some see it as a safety net, others see no need.
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[4SFED444]

I talked to Brian(BTS) when I got my trans and he recommended keeping the bypass.

I personally removed mine and have noticed no measurable difference in the amount of time the trans takes to come up to temp.

However I don't know if the earlier SD trucks came with a radiator trans cooler inline with the air/air as mine did. If you don't have a radiator trans cooler I would keep the bypass.

 

[444-4D]

If you don't have a radiator trans cooler I would keep the bypass.

Why would you think that? Is it because you have been convinced the cooler in the bottom of the radiator warms the fluid?

SD's got the radiator cooler added in March 2000 IIRC.

 

[4SFED444]

Why would you think that? Is it because you have been convinced the cooler in the bottom of the radiator warms the fluid?

I wouldn't say I was convinced, but there has to be some type of heat transfer one way or another(convection), thats simple physics.

I did do a little research before ditching the bypass. I noticed on my dad's '04 6.0 PSD SD the trans had no bypass. The rear trans line ran to the radiator then to the air cooler and back to the trans. I ran mine the same way and upgraded the lines to braided SS. My belief is if Ford did away with it, it is not necessary.

 

[Mark Kovalsky]

I wouldn't say I was convinced, but there has to be some type of heat transfer one way or another(convection), thats simple physics.

Absolutely there is heat transfer. The heat ALWAYS goes from the trans fluid to the radiator. Always. Without exception. The radiator is NEVER warmer than the trans. I've measured temperatures in the radiator and in the ATF going to and from the radiator. I've run tests as cold as -40 and as hot as 115 ambient temps. The radiator ALWAYS cools the ATF.

I did do a little research before ditching the bypass. I noticed on my dad's '04 6.0 PSD SD the trans had no bypass. The rear trans line ran to the radiator then to the air cooler and back to the trans. I ran mine the same way and upgraded the lines to braided SS. My belief is if Ford did away with it, it is not necessary.

You didn't do enough research. Ford did not do away with the bypass, they moved it inside the trans where you can't easily remove it. It is now in the pump body, and it also is a thermostat. It only sends 10% of the normal flow to the coolers until the trans is warmer than 165F.

 

[4SFED444]

So do you think removing the bypass will harm my transmission?
Even on cold days I average between 120-135 deg F. I was still below 140 deg with the bypass.

On 90+ deg days, towing 5 tons, my trans temp has never been over 165 deg F since removing the bypass. Before I would venture slightly over 200 deg and that made me uncomfortable.

 

[Mark Kovalsky]

The temps hot or cold are not relevant.

The 4R100 bypass doesn't bypass the coolers to help warmups. It only bypasses when the cooler is plugged. Extreme cold, like below 0F, can plug a cooler. Debris in the cooler can do that, too. In either case the bypass will open when the pressure in the line to the cooler gets too high. If you don't have the bypass and the cooler plugs you don't get any flow to rear lube, and the rear half of the trans will self destruct. You'll see this in the temperature gauge AFTER the damage has been done.

 

[gregrob]

In my case (uncle's truck) the cooler was plugged, and the bypass didn't seem to be doing it's job.

When we bypassed the cooler ourselves, and forced fluid right back to the rear of the trans, temps came down, light's, sirens, bells, and whistles went off, and the truck made it another 1200mi home.

 

[444-4D]

In my case (uncle's truck) the cooler was plugged, and the bypass didn't seem to be doing it's job.

Doing it's job? It's a hollow tube. The end of the tube is covered by a 7/16" steel ball. The ball is held in place by a spring. Either you have enough pressure to push the ball off the end or the tube or you don't. Not much to fail in one of those things.

 

[gregrob]

Doing it's job? It's a hollow tube. The end of the tube is covered by a 7/16" steel ball. The ball is held in place by a spring. Either you have enough pressure to push the ball off the end or the tube or you don't. Not much to fail in one of those things.

Theny why do they fail.

 

[444-4D]

Theny why do they fail.

Send one to me that has failed and I will tell you why that one failed. I'm guessing most of the ones that get replaced have nothing wrong with them.

 

[gregrob]

Send one to me that has failed and I will tell you why that one failed. I'm guessing most of the ones that get replaced have nothing wrong with them.

I'll see if he still has it.