So I have had this trans rebuilt locally by a guy and it wasn't right from the beginning.
Then I sent my truck with a family friend who teaches at the automotive college.
He had pulled the trans out and looked it over and "fixed" a few things he said were out of spec.

Trans went great until I added some hp. It shuddered and slipped.
So
I took it to a trans place that I usually get stock transmissions built, the guy has done them for me around 15 years now. I trust him.
I took him for a ride and he quickly told me the trans cooler was plugged or a cooler line was pinched...
Is this possible. He said the pressure on the feed side was too high and it causes the servos to no be able to release and engage correctly.

I really don't want to yank this thing out again or spend any more money on it.
I have another cooler but was just curious if I'm just wasting my time and money.

 

Subscribing! Interesting question.

 

Could it be the pressure bypass is stuck open? Disconnect the return line at the cooler and if there isn't any flow when the truck is running then the bypass is open. Not that uncommon on a 4r100.

 

I forgot about that stupid temp/pressure bypass piece of crap.
Ill get them to check that. (I'm 650 miles from the truck)
I was tempted to delete that on my hotrodded truck like I think bts does. But the other trans guys don't.
I should look up the price of a replacement.

 

Yes, it is possible that the coolers are plugged or a line is pinched. No, it isn't possible that a plugged cooler circuit is causing your problem. As for the servos not being able to release? The only servo in the 4R100 trans is used when the shift lever is in the 2 position. Any other time it's just along for the ride. There are ZERO servos used when the shift lever is in D. So I question if this person knows anything about this trans, and if he does, is he just taking you for an expensive ride?
Yes, the bypass could be stuck open. No, it won't cause a shifting problem if it is stuck open. The only problem it can cause by sticking open is higher temperatures. Thanks for playing, bad guess though.
They are not expensive. They also are NOT a temperature bypass, it works strictly on pressure. It also cannot cause your problem.

I believe BTS does not delete this. They are smart enough to know that if you delete it and do get a restricted cooler circuit your first indication that there is a problem is that the transmission self destructs. If you have the bypass and get a restricted cooler circuit your temperatures go up, but the trans lives. You have an indication there is a problem and time to fix it. But the choice to delete it or not is yours.

There is another builder on the west coast that I believe does delete it, but he doesn't seem to understand how it works.

Now that I've debunked all that nonsense, back to the original problem.

How much power did you add and was the trans built to take that much power? Was the program updated so that the pressure in the trans compensates for that much power?

 

BTS keeps the bypass. JW eliminates it.
You can easily rebuild the bypass tube/valve with this kit: Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts

 

Sometimes just got to throw it down field to see what happens.

 

I knew one of the big power guys eliminated the bypass. Just couldn't remember who.

Thanks Mark. I was hoping you'd drop in.
The trans guy was talking to my father, and my father added in the extra nonsense I'm sure. He's a c6 guy.

The truck got an sct programmer tune. Just the lowest setting it had because that truck has no gauges and it hasn't been run a whole lot.

I'm sorry I'm not much help. I'm trying to diagnose this problem from 650 miles away and with second hand info.

 

Mark...
Update. I got a message on my phine from my father saying that its mostly being weird in reverse.
Now I'm getting more background and some of the story (woulda been nice earlier huh)
He said when you put it in reverse it loads the motor up and tries to stall out. It will back up but it's weird. Occasionally when you come to stoplight it will try to stall or keep going. kinda like converter is t unlocking. But when you're driving the truck and tap the brake, it will unlock the converter just fine and reengage smoothly.
So the shudder I mentioned earlier was at a stoplight apparently. Not from extra power.
I was sure that they put a new converter in when the trans was rebuilt the first time.
What else would cause the trans to load up the engine when in reverse.

 

The ONLY way the trans can load up the engine is with the torque converter.

The converter clutch can drift on from several causes. Low trans fluid, loose/missing internal filter, leaking seals, sticky torque converter clutch solenoid or valve, or a wiring problem.

 

Gotta pick your brain again Mark.
Late 99 F350, newly rebuilt trans still iffy.
I haven't been involved with the investigating and repairing of this thing so I'm sorry.
Trans is better than before, but still weird.
The trans guy my father has gone to is saying that the trans cooler is plugged, causing a hitching/slipping in reverse. I told him to pull the cooler off my other psd and put it on and check. It's a long slow process.

Mark, is there any reason for a plugged cooler to cause a "low fluid" type slippage or hesitation in reverse. This is getting on my nerves. I've got enough money into this pile of crap I coulda added a little extra and bought an hd4r100 probably.

The bugger is that I was at the truck during Easter and the darn truck started blowing the fuel pump fuse and I couldn't drive it. Being limited on time I said screw it and I worked on other stuff. Now the pump issue is fixed but I can't give exact details on trans issue.

 

I don't see any way a plugged cooler could cause hitching/slipping in reverse.

There is a bypass on the side of the transmission that will open if the cooler is plugged so that normal flow is maintained with a plugged cooler. The trans will get hot, but it will function normally.

 

That's what she said.......