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The trans itself is an older ATI built unit (1998 to be exact), it was one of their higher end units at the time. Per the serial number on the case, John Lane at ATI decodes it as:

It has 5 clutch in fwd, 4 direct, 4 intermediate, direct drum is aluminum, vasco input shaft, HD center support, 4340 clutch hub, and a griner valve body. It was a fuel blown transmission back then but in today’s wording it is an upgrade on our 401360. to make it a fuel comp it needs the big aluminum drum and more clutches and a vasco intermediate shaft.


When I bought it it had burnt direct clutches on supposedly very few runs. Builder said the intermediate clutch stack gap was too loose so he tightened that up and we later found out the test port pressure was too low (145psi warm under load, which we adjusted up using TCI 200-220psi spring that actually makes 200 cold and 185-190psi hot in fwd gears, and 70-75 in Park and reverse). So hopefully those changes cure that. He verified that the direct drum bleed hole is indeed drilled. And I've been meticulous about fluid level being at the pan gasket (marked dipstick while pan was off, check religiously once warm after drive). I'm using BG Products red 312 synthetic lube. I have modest sized cooler with a fan on the front of the car. According to the autometer thermistor, fluid temp in pan never exceeds 170°F. We double checked the shifter adjustment, it's all good. And should note that I feel like it drives and acts perfects (shifts are crisp, datalogs indicate no excessive slippage beyond expected converter losses, etc). The fluid push is the only problem I'm experiencing.


To today's subject. The underside of the car is wet on the passenger after hard passes. First I rigged a clear plastic bottle and hose to the vent tube to verify that it was coming from the vent, and then clamped my go pro under the car to see when it was coming. As it turns out, it comes 10-15 seconds after getting out of the gas and coasting down. See video here. Skip to 4:30 for first action. I make a few NA rolls, it finally pushes fluid after the 3rd pull. I make a nitrous roll after that, not knowing that it had already pushed some fluid (horn honk at 8:12 was my reminder that the next hit was sprayed).


http://youtu.be/HipYQGuoxXM


As you can see, the fluid looks foamed up when it comes out, which most say is an aeration problem (under full, shitty filter, forgot O-rings on pick up tube). My filter and pick up are an all metal assembly, definitely has both O-rings, and as above I'm certain the fluid level is at the pan gasket, warm, in park. It's an ATI deep aluminum cast pan and their pick up assembly if it's worth mentioning.


Popular sentiment from the rest is that it's over-full still. Last night I went out and continued beating around on the car, pushed a grand total of 5-6 ounces out.


Any opinion? ..I'm on a witch hunt right now, and we depart for drag week in 6 days! The car weighs 3620 with me. Made 530whp NA and 755whp on the plate, Dynojet numbers.


Please and thanks. Sorry about the novel.
TJ
 

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Discussion Starter #2
Here is inside the pan (mostly wanting to show the filter/pick-up in case it's an obsolete technology):


Here's a sample DL including trans temp. I drove and beat around for quite a while last night, DL the last swat and 170deg yet again.


I don't have a picture, but the builder that was in it for a refresh added the Rossler case-saver lug.


And as a side bar, another local builder insists that test port pressure needs to be even higher (250psi) along with another mod to the reverse boost valve large flange. After searching/reading several of the th400 conversations here, I feel like the 190-ish number I have now is more common. But would like to hear more on the higher pressure topic if you don't mind a few more key strokes.

Thanks,
TJ
 

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I emailed John at ATI and his response was that they still only target 165psi, and that I should have a reputable builder go thru it. I know he's not very chatty, but it wasn't very insightful feedback.
 

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Trans was built by ATI in 1998....

Direct clutch pack originally had 5 thin steels and 4 thin frictions. Pack was very burnt. Setting up the pack the same netted just shy of 100 thousanths. Reset pack with with 4 thin frictions, 3 thin steels and 2 thick bringing the pack to .047 (if memory serves.
 

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Your pressure upgrade is good. Stator support/pump surfaces need to be FLAT, check that out. The screen/tube inlet is somewhat restrictive but better than the pancake filter /plastic tube many have to use. If it were my trans, I'd be calling Coan for a direct drum, 5 clutch's @ .080, always use the thick steels, new, flat and not kolene.
 

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Since the line pressure, converter, and return are the passages adjacent to the vent in the pump, wouldn't a pump crossleak leak from the vent at all times or am I thinking of this wrong?
No you're not half baked. Good question. There is a hot soak situation to the equation. But, the key is to have a case that is not warped, a pump that has two halves that are flat. And there is only one word to describe flat and that is flat, LOL.

I see large horsepower to weight Outlaw cars often down here. And they generate considerably more heat on average than your graph is showing. Which leads me to ask where is your temp being taken? I suspect that the 170* number represented in that graph you shared is taken from the pan. So, I'll run with that thought... Come back from a hit or a long street cruise or whatever and jack the nose up so you can get under it safely. Then take an infrared temp gun and take temp readings at the pump cover near the converter snout, the converter hub, the converter itself and then the pan. You might be surprised at what you see.

We can see a 45 -60 degree difference between the pan and converter after a hit, and that's being conservative!

Keep in mind that the fluid path works like this... pump to converter, converter to cooler, cooler to rotating assembly for lube (in most cases) and then lube to pan. Then consider that the rotating assembly does not generate heat, the torque converter generate the transmission system heat. Therefore, if you have an inefficient torque converter and a sick nasty cooling system you pan temps will be reasonable, but your converter and pump are baking.

g
 

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You do have a slight problem but if you are wanting to go race, my suggestion would be to install an adequate sized catch can up high and run the trans vent into it with the allowance that it can drain back into the trans afterwards. If you want to fix it , you may need to lap the pump halves or control the cooler pressure to slow down the crossleaks. Its possible that it is only a 6 bolt pump/case and the halves are not properly seated to one another. The list goes on of possibilities.


Hutch
 

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Thanks for the responses guys. Pan temp is in rear bottom of pan. I'll infrared gun the forward end. Hutch I've had that suggested, let it push out and drain back in from a high mount catch. I'll do what I can for this coming week and then get it out for deep dive on pump flatness.

Thanks again.
 
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