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Discussion Starter #1
Hi Guys,

I have a 4r70w on my 2000 Ford Explorer with a 5.0 (Its a 347) with a rear mount turbo.
There is also a Lentech Valve body with the mid grade programming (Set up for 2400 stall)

I keep wiping out thrust bearings.
I checked all the usual, like tc pilot not forcing the crank forward. I also checked to make sure the tc needs to pull forward in to the flex plate.

What I 'think' is happening is that high line pressure is pushing the tc forward in to the flex plate.

Here's what I think the remedy is:
At one point, mounting the intercooler, the trans cooler hard line was cut to make room. A soft line pulled off, so my 'fix' was to flare the end of the hard line. Well, this line would not flare very well with the cheap flare tool I had. It turns out there was a bit of a crimp in the line, restricting atf flow. I replaced the cut lines with factory hard lines and used some longer soft line to route around the intercooler.

I also have a new tc from Circle D with a 2800 stall (Since I thought my old 2400 stall converter might be suspect, I took the opportunity to replace it with a Circle D unit with a higher stall.

I lowered the shift pressures in the tuning to factory, as I was thinking max commanded shift pressure (along with the Lentech valve body) is creating to high of a ATF pressure ate the tc. Is this a reasonable assumption?

I want to make sure I fix this, as I can't afford to keep rebuilding my motor. This will be my last rebuild, so I better find and fix the issue.

How do you guys check pressure at the TC? I'm told I need to check pressure at the atf cooler line (Lower line on the transmission that is going to the cooler). Its a hard line, and I am not going to cut in to it, so I need to figure something out for this.

Also, any thoughts on how to make sure there is no restriction in the atf cooler lines?
I guess I don't know how to do this, as the cooler holes are only so big in the transmission anyway. Going larger that that wouldn't make a difference, would it? The atf cooler flow is factory.. Out of the trans to the top of the radiator, out the bottom of the radiator to a factory plate sytle cooler, then back to the transmission. Its a solid line from the transmission to the top of the radiator.
 

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How many R's are you turning?

The words I don't see in your description of your TC are "Anti-Ballooning plate" or "Billet Front Cover".

Regular TC's are rated to some rpm, but they all expand front-to-back as rpms go up; they want to go round, like a balloon.

There are ones available with that in mind.

Check out this:

https://www.google.com/search?q=torque+converter+ballooning
 

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In Chevy trannys you see the hydraulic pressure drive it into the engine, but our tranny isn't built the same.

Our 'apply area' is less, so there's less force.

Unless you're making 500psi of pressure; that could be an issue. :)

The line pressure is programmable, so ask a tuner if they've seen this.
 

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Discussion Starter #5
Thanks guys,

I never could get an answer from the original tc builder on an anti balloon plate. Allthey would say was there's no way my converter was ballooning. So, time to go billet to be sure. Way cheaper to just throw parts at an issue sometimes. Besides, I think the higher stall will be a welcome change getting off the line.

The TC one from CircleD has a billet cover, so when the motor goes back in, I'm good there. It looks like a nice unit. Circle D Specialties. FORD 11" HP Series 4R70 Torque Converter

RPM's are around 6200, so I'm not exactly pushing things.

The pilot on the old TC was not pushing in to the old crank at all.
I'll be checking the new crank against the new TC pilot as soon as the new crank shows up.

I'm hoping I have all possibilities covered.
I appreciate the input, I just need to make sure I check, and re-check everything. I just don't necessarily know what everything is, as there seems to be some voodoo involved when this keeps happening.
 

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Discussion Starter #6 (Edited)
I do my own tuning, but Don Lasota is always extremely helpful as I'm no expert.
I did reach out to him, and he doesn't think having maxed wot shift pressures could cause this.
Just to be safe, I backed off shift pressures, and lowered the calculated torque table as that has a lot to do with trans pressures.

If I have the motor in for a while and the thrust bearing survives, I can always carefully increase this stuff again as necessary.
 
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