TH400 build-pictures

[chris718]

jason high rpm engines benefit from no check back on either side but a mandatory .060 bleed hole in the drum.hi rpm can cause balls not to seat.

[DonWG]

Originally Posted by chris718

don .002" per side is the amount left for the grinder to grind off to bring the valve to the proper dimension.this means if the part finished od is .750 its diameter is machined to .754 "after turning in the lathe .the final material removal to get to required diameter is done on a grinder while the part is supported on both ends from a center point machined into both end faces..002"per side removed generates .750".besides other things it allows "exact finishing and alignment between centers.

Good. I was hoping that was what you meant.

[DonWG]

Originally Posted by chris718

jason high rpm engines benefit from no check back on either side but a mandatory .060 bleed hole in the drum.hi rpm can cause balls not to seat.

Slick chirping 3rd on a sticky track with a checkball in the aluminum piston. 2-3 shifts have been as high as 7,800 rpm. This is in addition to a bleed hole (not .060"), commonly recommended to relieve trapped or crossfeeding oil, drilled in the high drum. I think the reason for this extra hole has been covered. The high drum is not rotating in 2nd gear and begins to rotate only after the pressure has seated the check ball, acted on the direct clutch piston and the clutch pack has engaged. Maybe at a lower line, the checkball can unseat due to rotating speed?

There is a better intermediate sprag setup, but I don't think you'll need it for your level.

[DonWG]

I was just thinking. Judging from your pictures, you're probably not dual feeding the direct, so the possibility of the direct airbleed checkball not seating at high rpm won't be a concern.

[chris718]

Testing i have done in the past has improved clutch apply with balls omitted in high rpm applications.Oil does momentarily exhaust out the ball on apply and it is this motion that partially pulls the ball into the pocket to create the seal.Hi rpm can throw the ball up the curvature of its pocket and away from the center and unseat it.Oil pressure acting on the balls minute cross section in psi is minimal at best,and there comes a point where rpm beats psi.

[DonWG]

Originally Posted by chris718

Testing i have done in the past has improved clutch apply with balls omitted in high rpm applications.Oil does momentarily exhaust out the ball on apply and it is this motion that partially pulls the ball into the pocket to create the seal.Hi rpm can throw the ball up the curvature of its pocket and away from the center and unseat it.Oil pressure acting on the balls minute cross section in psi is minimal at best,and there comes a point where rpm beats psi.

At what rpm did you notice the checkball having a problem staying seated?

There are many transmissions that use airbleed checkballs for the same purpose as the airbleed checkball in the direct drum or piston of the turbo 400, including the 200-4R. What other transmissions have you found this to be a problem?

[chris718]

right about 8000 rpms with a TH400.more prevelant with the 4l60 series where the drum is already in motion in 2nd gear.many have been doing it on torqueflites forever.even if you pump up a 400 or 4l60e drum with 200 psi you can easily push the ball off seat with little effort.the ball check is a very effective but when parts have hi mileage ball seats are worn out and then high rpm just aggravates it.

[DonWG]

8,000. Well, the only way I'll be doing that is by accident. I think most don't have to worry about that problem.

[chris718]

all of our stage 2 units are built with no ballchecks and the bleed hole regardless of rpm.it has worked well,whether its because of the ballcheck absence or not we dont have direct clutch problems.Don I suggest you try it and see if it improves your already functional situation.Its an easy enough thing to do.Some things have been passed over form one design to another without checking the value of their presence in a functioning system.Based on design standards currently in use ,most non rotating clutch housing wont employ a ballchecks,while rotating housing do.some rotating housing that dont use ballcheck will use a ball check and bleed hole in the case or valve body.this seats the ball on apply and bleeds off oil at an orifice next to the ball check to exhaust.as soon as pressure is dumped at the manual valve the ball drops and the ballcheck seat becomes the 3rd and second largest ehaust point in the circuit.But in most manual shift custom vbodys the clutches exhaust at the manual valve (except for the direct after brake charge is dumped.)applying the clutch as fast as possible is enhanced by its removal when used with a bleed.One of these carried over things has been the reverse boost circuit in a th400.it isnt needed in a manual shift brake equipt 400 with max line and we have left it non functional for the last 5 years.we also grind a slot into its land in the boost valve so it doesnt become hydraulically active from the common x leaks at the boost valve. why a ballcheck in the forward drum and none in the center support?it seems the non rotaing drum / piston rule has become standardized.no its because the forward drum can remain applied momentarily while shifting quickly to reverse and drive such as when you are stuck in the snow.the main thing to realize is that without testing some of this stuff may just be along for the ride,and the given application is the foundation the final result is supported by.

[DonWG]

Holy cow Chris. You made my head hurt. Ouch!

The constant bleed hole, especially if it's 1/16" is more than adequate to take the place of the checkball airbleed and exhaust any residual during unapplied conditions. I'm not saying it won't work. It does. Just make sure you do have that bleed orifice, constant or checkball airbleed.

I use both.

OK. I'll explain why I do it the way I do. Not saying my way is better than anyone elses. Like I stated in an earlier post, every builder has their own way of doing what turns out to function the same.

I drill a constant bleed orifice too. In the same place everyone else does. I don't drill it to 1/16". I just feel it's way too much of a constant bleed. I use a smaller size.
I also make sure I have a checkball airbleed. With both the checkball airbleed and the small constant bleed orifice that's positioned to relieve any trapped oil from the outermost point of the piston cavity, I have very adequate air bleed capacity during the initial feeding of the direct clutch. After the clutch housing is bled of air and the fluid slaps the checkball orifice closed, I will still have the constant bleed orifice bleeding off oil while the high clutch is applied and holding 3rd gear. Understand that any fluid that is bleeding off while a clutch is trying to hold is the same as if you took a razor blade and cut a bit of the clutch piston seal away. It makes no hydraulic sense to have an excessive bleed off going on when the clutch is applied. There you have it.

[chris718]

TRIMMED 350 STEADY REST RING IN LAST RING GROOVE

[DonWG]

Nope.

[chris718]

come on don,send it in an email anyhow there a good episode of the twilite zone on see you later.

[turbo bitt]

Chris,
This is another bearing support I'm playing with. It is hard to see but the pocket are under the last sealing ring is machined for a torrington bearing.

[DonWG]

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.

[DonWG]

Originally Posted by chris718

come on don,send it in an email anyhow there a good episode of the twilite zone on see you later.

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.

[chris718]

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.

[DonWG]

Originally Posted by chris718

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.

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.

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.

[lazaris]

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.