dburt86

iTrader: (2)

I built a motor over the winter and switched from a t56 to th400 (first auto) and within 3000miles, the thrust bearing is wiped.

I know I had a good amount of converter spacing of the trans pump so I'm assuming it was excessive converter charge pressure (I didn't even realize I needed be concerned of this)

I'm chalking it up as a learning experience and getting a new crank put in it (and whatever else it will need) but I'm also trying to avoid this again

So my main questions are

The trans and converter operated great. Had about 9.3% slip at 6200 rpm

I hear some people of putting a pressure dump that goes between the oil cooler out and goes back to the trans. Rossler sells them for 98$. Easy peasy, don't even have to open the trans.

Or I get the converter feed office restricted

Which one is better? And if the trans was working fine, could there be something wrong with it that caused it to kill my thrust?

Money is tight, but I'll have the trans gone through if we think there's a need

I'll post pics in a few

forcd ind

iTrader: (7)

Did the converter have a balloon plate in it-I also lost a thrust bearing, when I had my trans apart I did the mod. to lower charge pressure, but never checked it-there has been examples of modifying the thrust bearing to allow more oil on the sides, even a 2 piece bearing is out there. Some of the guys are adding the dump in the cooler line. Could just be bad luck, but seems I have heard of to many thrust bearings wiped out, maybe the center thrust is more prone to this than in the old gen 1 engines, or just more LS engine getting boosted than prev. designs. When I build another LS engine, I will address converter, thrust bearing, and charge pressure.

dburt86

iTrader: (2)

Im not sure if the converter had a balloon plate. Its a PTC 9.5

what would a balloon plate do? Ill google

dburt86

iTrader: (2)

So it looks like the term "ballooning" is exactly that.

So in a case like mine, would the thrust bearing be damaged from the converter swelling, and taking up the end play and pushing into the thrust bearing?

Or can the line pressure be too high, hydraulicly pushing the converter into the thrust?

Or could it be a combination of both?

Im basically asking if you had a very rigid converter (ballon plates, ect) could you still potentially kill a thrust from high converter pressure?

a05c

It keeps the converter hat from ballooning (expanding) and either taking out the thrust in the engine or the pump in the trans.

Nali6.2

I have anti ballooning plates in my converter and im still going to put a dump valve in the cooler line just in case. i read about th400s doing this way to often not to spend the money and have piece of mind. atf speed? makes a nice kit for a 400

Old Geezer

iTrader: (3)

Hi out psi has been an issue since the 400 came into use in hot rods...
Dump valve, or an orifice.
Doubt the PTC was build w/o a plate. I've had several.. Not 1 w/o.

Game ova

Take the pump off and split it. Tap the converter circuit feed hole with a 5/16 18, screw a set screw in and drill itty to .110. Cost under a dollar and will prevent this from happening again.

Forcefed86

iTrader: (4)

Check your trans pressures. Usually caused by running excessive pressure. Usually the trans slips and the owner complains, then they raise the pressure (to much) and the trans grabs and it wipes out the thrust. Kind of an on going battle between trans and engine guys.

http://www.tciauto.com/tc/trans-line-pressure/

Game ova

As long as the converter circuit is restricted, you can run as much line pressure as the pump can make and not have thrust bearing issues.

Forcefed86

iTrader: (4)

That's completely false.

There is no magic restrictor number. Without knowing more about his setup telling him to add a .1xx restrictor is a shot in the dark and can lead to more problems. Every shaft is different, not every pump will respond the same way to an orifice. Line pressure changes the diameter of a restriction to obtain the same pressure. Converters play a role , oil type has its effects and the list goes on.

Game ova

Other than MAYBE raising his stall speed slightly, restricting the circuit won't hurt a thing. I did make the mistake of assuming he's running fixed line pressure or not. But I can tell you that from the research I've done....along with my own personal experience. It's a safe bet that his 400 won't do this to him again if he were to restrict the converter feed. And it can be done without buying some fancy device. And if what I said is completely false, then my transmission should have blown up by now, because when I built it....i did exactly what I typed. No thrust issues.... no transmission issues.

truckdoug

iTrader: (25)

I run 80es but I think the same deal applies. I just drilled the pump body to bleed pressure as the HD2 kit indicated

I think can also get a special pump relief valve if you dont wanna drill. Denmah has a video about it.


just be thankful you're not running gen 5 motors...they only have half a thrust bearing!
poor guy I just met killed his lt1 with only 550wheel on a procharger set up.

tblentrprz

Any links to TH400 trans info you'd like to share? There seems to be a fine line in auto trans builds on how the complete system is setup. Variations with clutch material, stack tolerances, fluid type/viscosity, orifice size for charge and release circuits, pressure, etc all seem to impact the end product/performance. An excellent trans builder knows how all the pieces fit together and how the system is impacted/responds to a single change.

Thanks for sharing.

Game ova

I don't feel like wading through all of the related threads on the subject, but they can be found on the "Other" forum. I can tell you exactly how mine is set up though. Other than the 80e direct drum and transbrake, it's a bone stock 400. 6/3/6....70 direct clearance. 32 intermediate, didn't even check the forward drum. Other than the mods required for the brake....its just an everyday 400. It's currently behind a 740/1000ft/lb motor in a 3700 pound f body. It's really not all that complicated, 400s are known for having too much oil charge... gets worse when it's behind a turbo motor. Neck the charge down and it will be less stress on your thrust bearings. You can make it as complicated as you want, but it's really not.

dburt86

iTrader: (2)

I bought the trans used and it was built. From what i can see, its nice. SFI bell housing, moroso pan and dipstick, hardened input chaft, trans brake, TCI valve body ect.

I know that doesnt mean **** other then id be suprised if the orfice isnt already restricted.

And if it is, id think the cooler lines are being to restrictive.

Other question- Knowing that my transmission operated great, could there be an issue inside the trans that could cause this?

Basically asking if i should have this trans gone through even though its showed no indicator of needing anything (other then killing my thrust bearing)

dburt86

iTrader: (2)

PS- i dont know **** about these transmissions other then what ive recently learned.

asubennett

iTrader: (6)

hutch trans makes a simple AN6 male / male fitting that dumps cooler line pressure at 65psi, you can shim it for more if you want. 65 is really the most you want to see before the pressure pushes the converter into the crank wiping the thrust.

Also, super rigid flex plates facilitate bad things to thrust bearings. You want it to flex. A 99 dollar sri plate is great. A 400 billet flex plate not so great. My .02

dburt86

iTrader: (2)

I dont understand how dumping the pressure at the cooler lines could possibly lower the converter pressure unless either the oil cooler its self or the return path in the trans is the reason the pressure is high.

I know it works because alot of people use them, but i dont know how.

Forcefed86

iTrader: (4)

So it’s a pressure relief fitting set at 65 that installs in line with the trans cooler? Do you tap the pan to return the bypass pressure? Any pictures of this? I don’t see it on their website? I haven’t seen one that sounds like it installs that easily.

Thanks