Trust bearing !!!
- Thread starter GN280CI
- Start date
I been down that road no matter what happens for you to wear a thrust something has to push on it . I have seen poor maching work ,torque convertor balloning ,a tight convertor taking a long time extremely loaded lots of causes my advice find it before you put it back together .
Not beating the crank forwards and aft with the caps loose to alighn the thrust faces before you torque them:smile: Make sure the last blow is in the forward direction to align the rear faces
Sometimes if a cap is replace the thrust faces will not be aligned and it needs to be faced off square to the the main line. Ive used a .001 feeler gage with the crank pushed forward and checked to make sure the upper and lower thrust bearing is in contact with the crank thrust. Also if the return hole from the torque converter is to small it will hydralic the snout of the torque converter from back presure pushing on the thrust. Just some things to think about...
Sometimes if a cap is replace the thrust faces will not be aligned and it needs to be faced off square to the the main line. Ive used a .001 feeler gage with the crank pushed forward and checked to make sure the upper and lower thrust bearing is in contact with the crank thrust. Also if the return hole from the torque converter is to small it will hydralic the snout of the torque converter from back presure pushing on the thrust. Just some things to think about...It is unlikely the T/C is the cause. 400 trannies are FAMOUS for this. Why do you think that one fellow asked you if you were running a 400 trans?
DO THE SEARCH. READ THE THREADS.
I have seen people go through 3 crankshafts before they found the right fix. AND IT"S SO SIMPLE!
DO THE SEARCH. READ THE THREADS.
I have seen people go through 3 crankshafts before they found the right fix. AND IT"S SO SIMPLE!
Weakest Link
Member
- Joined
- Aug 20, 2002
You may be having the same issue I had with my 4.1 off-center motor. I reduced the pressure in the transmission when I am on the transbrake. The pressure was to high and was pushing the converter into the crank which was pushing on the thrush bearing. I hope this might help you.
This is the beautiful thing about the pump mod. With the pump mod, it pretty much separates torque converter pressure relative to main line pressure. You can run all the main line pressure you want and not worry about the T/C pressure being affected. There is still a relation, but it is practically nill.
Save Buick Crankshafts. Do The Pump Mod! Save Buick Crankshafts. Do The Pump Mod!
Ted. Please tell me you've done something to control converter pressures. Not main line, but converter pressure. I hate to see high end machines open to this kind of failure.
Don we have the pressures under control. My trans was done by Carl Rossler, he has done a great job with this issue and is aware of the issues the Buicks seem to have with excessive fill pressures. We checked the thrust bearing when we changed the heads from Champion to TA's. The bearing looked like new.
It makes me sick the damage that comes from these bearing going bad. I have learned a lot from those who have suffered from this and it has helped me out in what to look for. These bearing go REAL quick if things are not caught.
So far around 60psi or less on the brake is a good number to see. Not sure if more than that is acceptable. Maybe others can post some info on this so others can learn and save some headache.
It makes me sick the damage that comes from these bearing going bad. I have learned a lot from those who have suffered from this and it has helped me out in what to look for. These bearing go REAL quick if things are not caught.
So far around 60psi or less on the brake is a good number to see. Not sure if more than that is acceptable. Maybe others can post some info on this so others can learn and save some headache.
40 psi torque converter pressure has always been a good number for me in any type of application and for the past 20 some odd years since I've been modifying to guard against the possibility of this problem. I would not see any good reason to go over 60.
The key is the least amount of pressure to prevent any cavitation possibility. Any more is just pushing your luck.
For general knowledge. A correctly functioning stock THM400 will have a torque converter pressure of 40 psi without any mods. The pump mods are to guard against those few 400s that have an inherent problem controlling torque converter pressure. When you come across one on a trans dyno, it's not hard to recognize it as a potential crank killer.
The addition of racing mods adds to the problem.
The key is the least amount of pressure to prevent any cavitation possibility. Any more is just pushing your luck.
For general knowledge. A correctly functioning stock THM400 will have a torque converter pressure of 40 psi without any mods. The pump mods are to guard against those few 400s that have an inherent problem controlling torque converter pressure. When you come across one on a trans dyno, it's not hard to recognize it as a potential crank killer.
The addition of racing mods adds to the problem.
T/C pressure is kind a like mainline pressure. When it comes to mainline pressure, you run enough to prevent friction element slipping and burning for the given torque input from the engine, but not much over that because you're just wasting engine horsepower to turn the transmission front pump to obtain that higher main line pressure. Not to mention the extra heating of the fluid running at the higher pressure.
Too much of anything is not necessarily good.
Too much of anything is not necessarily good.
Not sure exactly how it works. I would rather use nitrous than cut flow feed to the torque converter, but I believe that's how it works.
If you restrict fluid feed to a low enough level or cut it off completely, the torque converter will start to cavitate. This effectively raises the stall of the torque converter, or more precisely, allows it to slip. A manifold pressure or rpm switch could be used to turn flow back on to the torque converter.
The big problem I see is when you turn off fluid flow feed to the torque converter, it will fill with air bubbles as it starts to cavitate. When you turn flow back on, it would need to fill the T/C as quickly as possible. That would mean a big feed orifice and possibly result in badly controlled T/C operating pressure. If a small orifice is used, the T/C operating pressure could be better controlled, but the refill time will be long, resulting in a soft launch as the T/C fills during the first part of the run. Depending on the car and setup, that may be preferred.
If you restrict fluid feed to a low enough level or cut it off completely, the torque converter will start to cavitate. This effectively raises the stall of the torque converter, or more precisely, allows it to slip. A manifold pressure or rpm switch could be used to turn flow back on to the torque converter.
The big problem I see is when you turn off fluid flow feed to the torque converter, it will fill with air bubbles as it starts to cavitate. When you turn flow back on, it would need to fill the T/C as quickly as possible. That would mean a big feed orifice and possibly result in badly controlled T/C operating pressure. If a small orifice is used, the T/C operating pressure could be better controlled, but the refill time will be long, resulting in a soft launch as the T/C fills during the first part of the run. Depending on the car and setup, that may be preferred.
- Joined
- May 28, 2001
Don helped me w/ the mod, some 10 yrs ago... Worked great!
X2...... I bought a modded pump from Don last year.
J-B Racing
Forced Induction
- Joined
- Sep 16, 2003
I blew my Thrust 3 times last summer. Always blaming on the AC Converter or the TH200 trans. When I pulled out the Engine, Rod #4 was Bent towards the Front. So maybe it's not always putting the blame on the Drivetrain!!
IMO
Joe
IMO
Joe
