Turbo 400 pressures

[lazaris]

What pressures on the transmission outlet line to the cooler (converter charge pressure) do the trans gurus shoot for? This transmission of course for use on the Turbo V-6. Main line pressure as well. With a reverse manual transbrake.

[lazaris]

TTT

[WE4]

200 psi is a good figure to hunt for. It should be warm as well.
When applying the trans brake, it will drop... then should return to approx. 5-7 % of what you had before pushing brake button.
I hope this helps.


Bruce
WE4
www.PTSXTREME.com

[lazaris]

Originally posted by WE4
200 psi is a good figure to hunt for. It should be warm as well.
When applying the trans brake, it will drop... then should return to approx. 5-7 % of what you had before pushing brake button.
I hope this helps.


Bruce
WE4
www.PTSXTREME.com

Bruce 200 psi for the oulet line to the cooler?? I thought it needed to be much less to prevent thrust failure?

[blackplague]

100 psi on the cooler out line.

[WE4]

I am sorry. You want less than 60 psi in the cooler line. Cooler discharge should be under 60 or so.
Sorry for the misunderstanding, but now you know what to look for for mainline pressures too.

Bruce
WE4

[lazaris]

Bruce whats the best way to acomplish this if lets say your main line pressure is for example 150-160psi or 200 for that matter. Should the converter feed be restricted so theres less charge pressure. Or do do just lower main line pressure? Thanks.

[chris718]

all pressures are derived from mainline pressure.therefore reductions in mainline pressure will reduce converter out pressure.70 psi is what youll find above 1200 rpms with a th400 and a perfectly flat good working pump with 200 psi mainline pressure.transmission coolers will increase this psi at a varyied rate depending on design.restrictive design coolers will greatly increase pressure on the outlet side of the cooler much like placing your finger over the end of a hose.increasing cooler line diameter and restrictions to flow in the system will in general reduce cooler pressure.

[lazaris]

On my unit built by CK for my V-6 application, I measured my main line pressure and my converter charge pressure (oil line out to the cooler). The main line was 210-220 and the converter charge pressure measured 80 psi with no coolers in place which is too high for the V-6 thrust to handle. Ask me how I know....

[chris718]

alot of engine builders are not familiar with setting end play on the v6 thereby increasig failures related to the elevated line pressure used in the transbrake applications.if you want to reduce line pressure a lighter pr spring can be used to combat this.several people on this board had thrust problems with their 3.8/th400 combinations and our pump cured the problem.coincidently it is the same pump used in all of our transbrake applications.staying on the brake for too long can cause this also.if you tap the crank with a mallet either front to back with a mallet you can easily remove the thrust in the crank and wipe out the bearings.it is important to measure the crankshaft endplay after the flywheel is bolted up to the converter to verify movement.simply prying on it front to rear after installation can reduce thrust failures.an understanding of these principles can reduce the chances of reocuring failures as well as reducing line pressure to the lowest possible level without inducing friction element slippage.

[lazaris]

Already using your pump and your unit which was specified for the turbo V-6. My measured mainline is 210-220 and cooler out line is 80psi. This cooler out pressure is apparantly still too high. This was tested with no coolers in place to eliminate any false readings. I've takin allot of different pressure readings and I'm gaining good information. I curious to see what some of the trans experts have done to lower the converter charge pressure.

[lazaris]

^^^

[chris718]

interesting to find out what information youve found in relation to the th400 and thrust bearing failure that i havent seen yet.it seems like no one else on the board has anything new on the subject besides what has already been discussed.

[lazaris]

Chris do you restirict the converter feed on the unit? What mainline pressure do you shoot for on the tranbrake V-6 applications?

[chris718]

we dont restrict the converter feed ,we just bleed off some converter charge oil when the pressure regulator valve opens.we also increase the converter charge feed on initial fire up to balance the valve and fill the converter faster .once it is full the oil circulates much faster due to centrifugical force within the converter.we also dump converter charge oil back to the suction portion of the pressure regulator valvetrain to reduce line pressure and converter charge pressure when converter speed and pump volume go up.this oil presses the valve against the spring to cutback oil pressure.we use 160 to 220 psi depending on the application.i like to see converter pressure at 70 psi or lower but end psi is dependant on individual application.when running 190 and above we mod the input shaft to reduce converter charge pressure also.

[chris718]

for a drag car we specify 160 to 190 psi.turbo v6 included.if the car will be street driven for long periods of time then you must raise the pressure above 200 psi or youll fry the direct clutches as they are on for ten ,twenty or 30 minutes with the bleed of and heavy return springs reducing clutch pack clamping force. i believe you specified you would be driving back and forth to long island dragway which is 40 miles each way and we suggested an aod. 2000 horsepower has been controlled by 180 psi with our pro 4 brake.now use this 180 psi on the hiway with bleed off and the pump not being able to keep up with it and youll fry the direct clutches in short order.a drag car will function with less than 190 psi indefinately,however because of the problems with main bearing journal diameter and the design of the thrust surface in the buick careful attention should always be payed in order to avoid failures.i can see where you are going with this ralph.im certainly not going to take responsibility for your thrust bearing problem.i will help you get the pressure to a level that you find acceptable.after a year and a half since the sale (if im not mistaken)i still have no problem with changing the pr spring at no charge.we stand behind our products 100%

[lazaris]

Chris I dont think you see where I'm going because I never asked you to fix my thrust bearing. What I did ask you was what you use for pressures and you told me it depends on the application and you know what my application is. I also never said I was going to drive back and forth to Long Island Dragway. Which by the way has been closed since last year. The track appearances I have made were all towed since gong to the 400. I tested the pressures, which indicate higher than what I was told. Im only trying to determine the cause, fix it and move on. Hopefully by posting my results of the tests and getting some guidence from the transmission builders will help someone when making the conversion and give them something to look for, to make a successful swap.

[BobbyBuick]

OK,guys Im the thrust take out GURU.
PSI X size of snout is=PSI against thrust
With that said Chris ,helped me repair mine after taking out two rotating assemblies.
I tried the orfice in the feed line to convertor and so did others TRASHED after about 50 passes.
What we did was bought Chris718s pump ,got tranny end play and crank end play to a minimum about .003.Shimmed convertor to I think it was about .060?
Also the main line pressure reduced from 210 to 140 psi with Chrises modified pump
I also do some modding to the thrust surface cutting a releif groove at a 45 on the parting half,oversizing feed hole to .250 ,and i cut a hole in the rear of the bearing half and chamfered it drilling into the oil galley with a 1/16" drill bit.
So far after two seasons good to go
Hope this helps

[lazaris]

Bobby,

I'm running the modded pump. Did you ever check the cooler out pressures before and after the changes?

[BobbyBuick]

I did but i really dont recall the differances.I think it was at 80 psi before