TH400 build-pictures
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IMO, figuring out ways to improve radial support of the direct drum is far and above more important than trying to add another thrust bearing location to the transmission. You guys spend way too much time on thrust problems that aren't there. No one can argue that there isn't a radial problem with the direct drum. You want to get creative? Focus on radial.
Chris. Let's not turn this fellows thread into a 'let's get Don's 400 build secrets' thread. And I'm not going to privately email them to anyone, either. Drop it, please. There are some things I experiment with and put into my personal trans only.
TBITT, That is where we install one as well.All forces in the 400 try to push the geartrain out of the back of the case .Supporting of the direct drum up front takes it out of the rear thrust equation and frees up horsepower in 1st and 3rd gears.Come on Don,I dont want your secrects,just was curious how you supported the drum.We dont have direct clutch problems where we are at now so there really is no need to invest more time in it.Our use of bearings is mainly for freeing up friction and horsepower loss.Perhaps focusing more on thrust and rotating losses would improve power transmission in everyones th 400 build ups.Hopefully this thread will get us all thinking and motivated to keep improving on an already stout design.Iknow it has given me some good ideas and things to look into by hearing other peoples thoughts.
The only thing trying to push the front unit (forward and direct clutch drums) rearward, other than G forces of acceleration, is lube circuit pressure. The thrust from G forces is manageable. The rearward thrust of the front unit is already supported by needle thrust bearings. That would be the sun gear to rear ring gear, and the rear ring gear to output shaft needle thrust bearings. The stock case thrust washer would be the only spot that would be causing hp loss from excessive friction. That spot has already been addressed by transmission builders decades ago. That would be the TH350 pump needle thrust bearing put in place of the OEM thrust washer setup. Old news.
Now, let's look at something very important. This is breaking news, first presented here, so read up. In the above paragragh I highlighted lube circuit pressure. How many of you have already figured out what might cause excessive rear thrust load in a 400? Enough to wipe out the OEM case thrust washer arrangement. The same way that the engine crankshaft thrust bearing can be taken out by excessive torque converter fill pressure.
Excessive torque converter fill pressure translates to excessive crankshaft forward push, which translate to short crankshaft thrust bearing life. Excessive torque converter fill pressure also translates to higher cooler line pressure (cooler line flow feeds the lube circuit upon return to the transmission case), which translates to excessive lube circuit pressure, which translates to excessive rearward push of the front unit in the transmission and excessive loading on two needle thrust bearings and one case thrust washer.
Are you guys seeing the picture yet? If you really want to free up horsepower and make your engine and transmission more durable, address the torque converter feed pressure in the T/C. If you're wiping out needle bearings in your transmission and feel you have to add more thrust bearing locations, your lube circuit pressure is too high and/or endplays are too loose or too tight.
This brings us back to the cause and effect that I've been preaching to you guys for years now. You must restrict the torque converter feed passage in the pump cover. It solves a multitude of problems and frees up horsepower.
Maybe now that everyone realizes that the pump mod can free up horsepower will make everyone jump on the bandwagon and do the mod. I'll bet people will be shooting for even less than 40 psi cooler line pressures now. Ha ha. :tongue:
Remember, the important spec when it comes to cooler lines is a flow of one quart in 20 seconds. I've even played with restricting cooler line pressure to zero and still had one quart in twenty seconds of flow.
Don,
If you reduce the converter feed enough limitting flow to the converter wont you then effect converter efficiency/slippage? Just something people should be aware of. I believe this is whats done to increase stall on the variable stall type transmissions.
If you reduce the converter feed enough limitting flow to the converter wont you then effect converter efficiency/slippage? Just something people should be aware of. I believe this is whats done to increase stall on the variable stall type transmissions.
turbobitt
Well-Known Member
- Joined
- Feb 14, 2002
Don,
Maybe you misread my post ? My intention is to constrain the drum using a needle thrust washer to reduce woble and instability, not to reduce friction. In the process of doing this, the front and rear thrusts are insulated so it doesn't influence the drum.
I am also under the same impression that CK stated in his ealier post that this has been over engineered for an problem nobody seems to now if it is a real issue. In any case, I will make my own insurance plan and do what I can to reduce drum instability. I am doing this for my own peace of mine and not for some competitive edge that is probably non-existant.
I would like to see data on stable vs. non stable drums and there applications.
Maybe you misread my post ? My intention is to constrain the drum using a needle thrust washer to reduce woble and instability, not to reduce friction. In the process of doing this, the front and rear thrusts are insulated so it doesn't influence the drum.
I am also under the same impression that CK stated in his ealier post that this has been over engineered for an problem nobody seems to now if it is a real issue. In any case, I will make my own insurance plan and do what I can to reduce drum instability. I am doing this for my own peace of mine and not for some competitive edge that is probably non-existant.
I would like to see data on stable vs. non stable drums and there applications.
Are they restricting, or turning off flow? And if they're restricting, what values (pressure and flow volume) are they restricting too?
The one case that I presented where I restricted cooler line pressure to zero was on a C4 in a mild street performance application. The engine builder and I were trying to figure out why he kept wiping the crank thrust on a SB ford. It turned out that the offshore cranks he was sourcing was the problem. But, I never did need to go back to the trans and increase cooler line pressure. The trans operated fine. Would I suggest that you go to zero? Probably not. I just illustrated that to show everyone that there may be some potential there. Those that like to experiment may find some hp there.
Lazaris. If I remember right, you stated before that you've tried some orifice sizes smaller than my recommendation. What did you find as far as T/C cavitation sensitivity?
I think I did catch that point. It's just that there is a better way. Stabilize the drum with radial support. More like the ATI system that was presented.
A more stable direct drum will mean better sealing ring and intermediate sprag performance.
When it comes to the chance of the direct drum contacting the sealing ring lands of the center support, if front unit endplay is correct and fresh bushings are used, that shouldn't be a problem. Yet, do to the fact that we know that the direct drum can have enough movement to contact the sealing ring lands is enough for me to do something to better support the drum radially.
Other transmission models that have been redesigned to better support the direct drum. Late model A500s, KM transaxle units, TH350 are some that come to mind.
Running the direct drum against a bearing takes all the rearward thrust generated up front and stops it at the center support.Now there isnt any except that generated due to the gear design.the output shaft ,rear carrier,front carrier and center support is 1 end play,and the rear ring gear and sun gear ,center suppot and forward hub is another.stand a complete rear section on the table from output to center support and pick up on the reaction carrier and see what happens.
Don,
im not sure if they completely turn off flow on the varible stall. When you did the test to reduce the pressure to zero is that the same as turning off flow completely?
I did try 3 different orifice sizes. 7/64 to start. It still started to take out the thrust. Main line pressure was about 235psi and the cooler out was about 55psi. I then went to 3/32 and lowered mainline to 165psi cooler out was about 40psi. Thrust was good then. I have since gone to 9/64 and the converter eff picked up 1% and I raised main line to about 180 now. But I also improved my exhaust pressure in the unit. I was able to raise the main line for improved holding while still making thrust the bearing live.
That's right Chris. I'm just offering that it's unnecessary to add another needle thrust bearing. The front unit is already supported by 3 needle thrust bearings if you count the one that is commonly used to replace the case thrust washer. How many needle thrust bearings do you really need? Are you seeing a repeat failure of one of the needle thrust bearings in the rear unit? I'm not.
It's easy to look at a location in a trans and say, "Hmmm, I could fit a needle thrust bearing there". But, is it really needed. What data or experiences are you using to justify the need of a needle thrust bearing there? It's a great marketing gimmick, but is it really needed?
No. In that case, bringing the cooler line pressure to zero still maintained a cooler flow of one quart in twenty seconds. Flow was not cut off.
I would recommend to people that if you're going to be breaking in a new engine and thrust bearing, make sure you do it with a relatively low transmission line pressure, which will translate to lower cooler line pressure in most cases, and certainly did in Lazaris' case. This will put the least amount of load on the crank thrust until it has had a chance to bed in and create a broader load bearing contact surface.
Main point being. If the planned line pressure is going to be 235 psi on a manual valve body, you are going to have 235 psi or close to it at all engine rpms, throttle positions and loadings with a manual valve body. As Lazaris showed, an exceptionally high line pressure will affect T/C feed pressure and cooler line pressure, even with the pump mod. I would have thought 55 psi would be safe, but evidently not.
Special note: Crank killer 400s don't care what the line pressure is. That's why you should always do the pump mod on every 400. Better safe than extremely sorry.
It isnt a marketing gimmick.It is the differnce between a product that gets the job done marginally and one that gets the job done more efficiently.It is what makes our product unique.We build 400s regularly for over 1200 horsepower.a quick look at the parts on the 400 competition components page should make this evident.Running the drum against the support reduces the front sections rearward thrust load on the rear section.Thrust is a motion.Power is absorbed to generate motion.There shouldnt be any question in anyones mind that a roller bearing installed between 2 parts is more efficient than a washer when the 2 parts are rotating opposite each other or one is stationary and the other is rotating.Rotation is a motion.Power is absorbed to generate motion.Bearing assist rotation and provide free momentum.Running the drum against the support and putting a bearing on the pump support(although thrust is rearward the bearing allows super tight clearances) allows front end play of less than .006".guess what?if the drum is pushed into the support and supported ,wobbling is reduced to close to 0.as far as restricting the cooler feed to 0 and still getiing 1 quart every 20 seconds ,at quick glance it would have to be a cooler bypass circuit doing its job,but who knows .and the 1 % gain in efficiency from converter charge sizing isnt something i would consider to be accurate as it is too small to be proven to be a gain and not test variations,or differentials in temp etc.
Chris. If a builder has added the needle thrust bearing at the rear of the case, there is no thrust 'washer' absorbing hp due to friction. Your argument is that needle thrust bearings do a better job of controlling friction losses. I agree. With the rear thrust washer replaced with a needle bearing, all you have taking up thrust load is "needle thrust bearings". Why add another? Even with needle thrust bearings, the more you add, the more frictional losses. Help me understand.
I agree with you on the 1% gain.
Talking about a C4. No cooler bypass. On that particular case, I restricted the T/C feed in multiple steps and watched the cooler line pressure drop in steps too. The engine builder kept having crank thrust problems with each step. That's why we did end up going to the extreme of 0 pressure. We were curious to see if he would still have a crank thrust problem with 0 psi. He did. And later other SB Fords he had built started coming back to him with crank thrust problems. That is when he finally concluded that the crankshafts he was getting were the problem. He was forced to close his business due to the liability incurred due to the cheap crankshafts.
Adding one to the front takes any rearward thrust from the front and cancels it at the support.Reducing front end play with the bearings reduces drum wobble by removing drum tilt plane.The bearing reduces power used to accellerate the drum and gives it momentum as it spins.Now the little bearing under the sun gear isnt overloaded,or required to do extra work.The rear sun gear bearing DOES take a beaten in all applications ,especially high powered cars.as for the c4,i dont build many but if you completely closed off the feed to the converter where it pees out the pump gear area the charge volume should be 0 if there is no pressure or oil supply unless it has a bypass .you probably didnt close the feed off completely .
Anytime you have added another thrust bearing element, whether it is a washer or a needle thrust bearing, you have added to thrust bearing frictional losses. You've just taken some load off of some and added another load bearing point that has its own frictional losses value. Whether the total thrust frictional losses was added to or taken away by the addition of another thrust bearing location, I can't say. I would guess that you've added to total thrust bearing frictional losses by spreading total bearing load amongst more locations.
Back to the C4. I don't know where you guys are reading that I completely closed off T/C feed oil. I 'restricted' it with orifices of various sizes. You'd be amazed how much flow you'll get from a 1/16" hole.
Yes, you can have flow with minimal pressure.