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Old Jul 25, 2009 | 10:20 PM
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Trans Bypass Line

Just wondering if anyone in the FTE world, knows the ford part number off hand for the transmission bypass line? I think mine has crapped the bed, and in need of a new one. And yes, I know of Diesel Site's(awesome site, I must say). Any help would be appreciated.
 
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Old Jul 26, 2009 | 12:38 AM
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Why do you believe the bypass is bad?

Is the trans overheating?

Pop
 
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Old Jul 26, 2009 | 09:26 AM
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Old Jul 26, 2009 | 11:33 AM
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It gets warm on the smallest trips around town. Gets to around 200 degrees when driving in the city, and around 190ish on the highway, with 80 degree ambient temps. So I'm pretty sure, the spring is shot in the ball valve. It also has aftermarket cooler and such.

Also thanks for the links, now just need to check them out and make some phone calls come monday.
 
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Old Jul 26, 2009 | 06:17 PM
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Amazing how things work. I just got home with the Travel trailer in tow (7200 lbs) and it was only a 10 to 13 mile trip home the trans started out at 150-160 where it usually runs with no load and then it usually gets up around 175 loaded. When I pulled in the driveway at home it was at 205 and ambiant temp was around 85-87 out. I have a feeling my thermal bypass switch in the tranny has went as well. Any other ideas out there? Sorry for the Hijack
 
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Old Jul 26, 2009 | 08:19 PM
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Originally Posted by racincowboy
I have a feeling my thermal bypass switch in the tranny has went as well.
Think again. There is no thermal bypass in the 4R100 transmission. There is a pressure bypass.

When the pressure bypass opens it is almost always because the cooling circuit is restricted, usually due to a plugged cooler. Changing the pressure bypass won't fix this.
 
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Old Jul 26, 2009 | 08:24 PM
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...unless it's stuck open. Before I messed with the bypass, I'd make sure the cooler isn't clogged first like Mark is suggesting. Outside first with mud or grass or whatever, then inside by doing a flow test. We have seen a few of these fail, so it's not exactly an impossibility.

I just put in a 6.0L trans cooler and couldn't be happier! Runs around 140ish empty. Used to be around 190.

EDIT: Pics are worth a 1000 words, right? These were both taken after the same 30 mile drive in about the same ambient outside temps:
 
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Old Jul 26, 2009 | 08:50 PM
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Originally Posted by Mark Kovalsky

When the pressure bypass opens it is almost always because the cooling circuit is restricted, usually due to a plugged cooler. Changing the pressure bypass won't fix this.
If a cooler were to clog, wouldn't you have more issues since now you got foreign materials clogging your cooling system? Just a thought...
 
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Old Jul 26, 2009 | 08:54 PM
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Thanks for chiming in Mark. I was hoping you would see this. I just noticed I put thermal instead of pressure must be heat stroke setting in.

So Mark would you suggest doing the flow tests like on I think it was Dieselsite.com?

If it turns out to be the cooler that is plugged what kind of things could have caused that? The trans was rebuilt about 18k ago. I will have to check my paperwork I dont remember if they changed the cooler or not. I do not have my tru cool on there yet any suggestions on installing that as well. If the stock cooler turns out to be plugged I will be putting in the 6.0 cooler just for good measure.

Anyone that has installed a 6.0 trans cooler how does it bolt up in there ect. Do you have to remove anything to get to the bolts that hold in the trans cooler? Everything I have read about this the 31 row is the way to go and it will bolt in the stock location correct?

Thanks for the help as always FTE is the 1st and best.

Would you also suggest running a magnefine filter in-line as well?
 
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Old Jul 26, 2009 | 08:56 PM
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Originally Posted by distortedcloud
If a cooler were to clog, wouldn't you have more issues since now you got foreign materials clogging your cooling system? Just a thought...
No, that's why the pressure bypass is there. If the cooler were to clog (internally), and there was no bypass, the back part of the trans would be starved of fluid and quickly destroy itself. If the cooler is stopped up, it'll just run hot. Still needs to be fixed, but at least you're not out a trans in the mean time.

EDIT: But yeah, you'd really need to know why there's junk in the cooler. I missed that little detail in your post... LOL
 
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Old Jul 26, 2009 | 09:01 PM
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But wouldn't there have to be some object causing a blockage? If that were the case, you'd have more issues since there would be foreign objects in the fluid. Also, just wondering, have you heard of anyone having a cooler clogged? Be interesting to find out the cause.
 
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Old Jul 26, 2009 | 10:45 PM
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Originally Posted by Mark Kovalsky
Think again. There is no thermal bypass in the 4R100 transmission. There is a pressure bypass.
In the last couple of days I've seen the myth of a thermal bypass perpetuated at least twice.

And yes, if your cooler, or even external filter, is clogged, you've already got much bigger issues brewing.

Pop
 
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Old Jul 26, 2009 | 10:56 PM
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Originally Posted by distortedcloud
But wouldn't there have to be some object causing a blockage? If that were the case, you'd have more issues since there would be foreign objects in the fluid. Also, just wondering, have you heard of anyone having a cooler clogged? Be interesting to find out the cause.
Yep, my trans cooler was clogged.....the firts PI torque converter chewed itself up and sent the debris downrange. Did the flow test and it wasn't pretty. Lots of greyish red tranny fluid with plenty of metal flakes.

I would do the flow test and get the bypass line, you could always return it if you don't use it. Like Mark said - if you just replace the bypass line you could easily be in the same situation. I changed my bypass line and it didn't make a difference. Then I did the flow test and found the bigger problem.
 
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Old Jul 26, 2009 | 11:26 PM
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Originally Posted by white Buffalo
Yep, my trans cooler was clogged.....the firts PI torque converter chewed itself up and sent the debris downrange. Did the flow test and it wasn't pretty. Lots of greyish red tranny fluid with plenty of metal flakes.

I would do the flow test and get the bypass line, you could always return it if you don't use it. Like Mark said - if you just replace the bypass line you could easily be in the same situation. I changed my bypass line and it didn't make a difference. Then I did the flow test and found the bigger problem.
Rich,

Good first hand knowledge post. Reps to you.
 
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Old Jul 26, 2009 | 11:37 PM
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Originally Posted by SpringerPop
In the last couple of days I've seen the myth of a thermal bypass perpetuated at least twice.

And yes, if your cooler, or even external filter, is clogged, you've already got much bigger issues brewing.

Pop
I'm not sure what you're saying here, Marv. I've seen several members here replace them which fixed problems. Not sure what else I can say. Like anything else mechanical, they can and have failed.
 
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