74Corvette
Member
Thanks Maniacmechanic1 I appreciate your help and effort on this. That is an excellent manual.
Th400 Oil Cooler Line Maximum Pressure
- Thread starter 74Corvette
- Start date
Maniacmechanic1
solid fixture here in the forum
No problem.
Go on ebay and look for your 1974 Corvette Service manual.
When I find used for $10-30 dollars I buy.
Guys have them also on Compact disc.
Pull up on your laptop at will.
74Corvette
Member
After seeing the main line pressures from all multiple sources I definitely have higher main line pressure then stock which I assume is giving me higher torque converter and oil cooler pressures. I never modified the trany but looks like the previous owner may have based on my pressure readings. So I put the car on blocks and just pulled the pressure regulator valve from the trany. For some reason the valve has been modified by grinding one of the control steps on the converter charge passage step. See attached pictures. Does anyone know why this would have been done? I am guessing that the result of this would cause more oil to flow into the converter. Could this be causing excessive converter/oil cooler line pressure? I also assume the spring in not stock.
Maniacmechanic1
solid fixture here in the forum
They all did their thing stuff like I said yesterday.
Some guys say no fancy parts are required in a Turbo 400.
Not even a shift kit.
It's Hydraulic Rocket science and much still kept secret.
I spent 1 year researching on my own.
Grump has some limited information.
Quite a bit was posted on Yellow Bullet Drag Racing Forum.
Top dogs having online forum debates and wars.
Has carried over to Facebook closed groups now.
Lately all Tight lipped.
A Turbo 400 is used in All Low level Street Outlaws and Pro Mod Street Outlaws.
Top Dog Big Chief uses a Turbo 400.
When unsure...use stock unmodified parts.
Means having a spare core TH400.
Unmolested original valve body and steel separator plate.
Transgo 400 Pro my choice of shift kits.
I have to read up later tonight in a book I have.
Ron Sessions book....The Turbo 400 Hydromatic.
Best book on Turbo 400.
Out of print.
I paid $120 something own it.
74Corvette
Member
Ok thanks again, I was shocked when I saw the valve had grinding done to it. The grinding was done on 4 sides, 90 deg apart and clearly done with a hand grinder as the fillets are not equal and the ground surface is very rough.
I am with you on the unmodified parts. Going to start looking for a another valve right away.
I am with you on the unmodified parts. Going to start looking for a another valve right away.
T-Test
solid fixture here in the forum
The valve mod was done for the stall convertor to lock up quicker than normal at the specified RPM with no slippage. I always did this with a shift kit install and never had problems in over heating the fluid or cooler.
Look in trans manual and make sue that pressure is within LIMITS which can be high or low.
74Corvette
Member
Ok thanks. Do you know what approximately the oil cooler line pressure range is? I am having a real hard time finding the oil cooler line pressures. The main line pressure is readily available but not cooler pressures. My concern is if the cooler pressure is too high the torque converter could cause a thrust bearing issue.
Maniacmechanic1
solid fixture here in the forum
I have never checked myself.
Threads on Yellow Bullet Drag Racing discuss in depth.
I have been using bone stock TH400 thus far.
Have 2 I will finish building this year.
One for Towing
Another Street Race for my 63 Gp.
T-Test
solid fixture here in the forum
From Drag Stuff.Com
Re: Trans pressure and converter coupling
Re: Trans pressure and converter coupling
#3 Post by wikd69 » Fri Dec 09, 2011 3:53 pm
HPDRIFTER wrote:Too much transmission pressure will push the torque converter forward, away from the transmission and wipe out the thrust bearing on the main bearing. Everyone has their own ideas about what is the correct pressure and how to limit it.
Shown below is the result of high trans pressure in a TCI built TH400 - originally bench tested between 240 - 250 psi line pressure. I researched this afterwards and read that standard BBC main thrust bearings are designed to handle upwards of 225 lbs of forward thrust. Any more than that and you start pushing through the oil cushion eventually wiping thrust bearings and smoking the crank like I did here. When I caught it, the crank had around .075 end play and the rods where starting to blue the block main journal bosses. Ugly.
My local trans guy (Jim at ATO) told me he typically sets line pressure in a TH400 at around 200 psi. Anything beyond that wears the pump out more quickly and contributes to heat issues in the trans. Without setting something up on a trans dyno, I have no clue how to measure the about of forward thrust resulting from a given trans line pressure. I do trust my trans guy tho and will limit internal line pressures to no more than 200 psi going forward. I belive you set line pressure in a TH400 by adding/removing shims under the bypass valve spring.
I dunno how this might compare to a Glide setup, but converters are converters and I would think they would all behave the same, regardless of which transmission they sit in front of. Having said that however, the '200 psi' rule of thumb for a TH400 may not apply to a Glide setup.
Your own mileage may vary. Hope this helps.
74Corvette
Member
Ok thanks again guys. I have also done hours of google cooler line pressure and have a stiff scrolling finger and red eyes from all the info to go through. I am not a trany guy so when I teed in a pressure gauge on my cooler line I was shocked to see 75-80psi as I have always thought the cooler lines where low pressures. Which got me concerned about the thrust bearing issues I have read about. If 200psi main line is a good rule then I guess I am ok at the 185psi main line I have in L1 & L2, lower in D. Assuming a small block 350 has the same thrust load capability as a big block.
Maniacmechanic1
solid fixture here in the forum
The Transmission oil pressure to to the clutches is 1 Entity.
The Cooler line pressure is entity 2.
Not related entire in a Turbo 400.
It's unique how it's done feeding the torque converter with oil.
With a Restricted drilled converter feed passage. Limits pressure inside of the torque converter.
Maniacmechanic1
solid fixture here in the forum
Driving. All I can post now
Maniacmechanic1
solid fixture here in the forum
Maniacmechanic1
solid fixture here in the forum
Somebody could have mixed up the input Turbine shaft from original .
Maniacmechanic1
solid fixture here in the forum
https://www.google.com/amp/s/www.hotrodders.com/forum/th-400-cooler-line-pressure-224757.html?amp=1
More to read.
I recall 110 psi max cooler pressure.
They state 100-109 psi max cooler pressure.
Not same as line pressure.
More to read.
I recall 110 psi max cooler pressure.
They state 100-109 psi max cooler pressure.
Not same as line pressure.
Maniacmechanic1
solid fixture here in the forum
https://www.google.com/amp/s/www.pirate4x4.com/forum/general-4x4-discussion/848892-pressure-th400-oil-cooler-line.html?amp=1
No flaw as one guy states.
People not knowing what they are doing making mods.
Transgo Pro 400 shift kit makes any Turbo 400 good for 800-1000 Hp with a Somnax Billet Foward Hub.
Nothing else.
Aftermarket drums added with Transbrake good for 2000 Hp.
Want a Transbrake.. only one reason to have that much power above 1000.. Full Drag race.
Up to 2000+- 5000 Lots of secrets held.
Know about 80 % what's done Pro Mod Street Outlaws.
Mine will be good for 1000+ in 63 Gp when done.
No flaw as one guy states.
People not knowing what they are doing making mods.
Transgo Pro 400 shift kit makes any Turbo 400 good for 800-1000 Hp with a Somnax Billet Foward Hub.
Nothing else.
Aftermarket drums added with Transbrake good for 2000 Hp.
Want a Transbrake.. only one reason to have that much power above 1000.. Full Drag race.
Up to 2000+- 5000 Lots of secrets held.
Know about 80 % what's done Pro Mod Street Outlaws.
Mine will be good for 1000+ in 63 Gp when done.